extfieldsofstudy: Mathematics Medicine

text:
Motor Program Transformation of Throwing Dart from the Third-Person Perspective

The perspective of perceiving one’s action affects its speed and accuracy. In the present study, we investigated the change in accuracy and kinematics when subjects throw darts from the first-person perspective and the third-person perspective with varying angles of view. To model the third-person perspective, subjects were looking at themselves as well as the scene through the virtual reality head-mounted display (VR HMD). The scene was supplied by a video feed from the camera located to the up and 0, 20 and 40 degrees to the right behind the subjects. The 28 subjects wore a motion capture suit to register their right hand displacement, velocity and acceleration, as well as torso rotation during the dart throws. The results indicated that mean accuracy shifted in opposite direction with the changes of camera location in vertical axis and in congruent direction in horizontal axis. Kinematic data revealed a smaller angle of torso rotation to the left in all third-person perspective conditions before and during the throw. The amplitude, speed and acceleration in third-person condition were lower compared to the first-person view condition, before the peak velocity of the hand in the direction toward the target and after the peak velocity in lowering the hand. Moreover, the hand movement angle was smaller in the third-person perspective conditions with 20 and 40 angle of view, compared with the first-person perspective condition just preceding the time of peak velocity, and the difference between conditions predicted the changes in mean accuracy of the throws. Thus, the results of this study revealed that subject’s localization contributed to the transformation of the motor program.

Introduction
Throughout life, subjects develop a perception of their actions from the first-person point of view. At the same time, in some situations, the subject is given the task of regulating his own actions when he perceives himself from an outside perspective, for example, in a mirror during rehearsals and trainings, while controlling an avatar in computer games using virtual reality (VR) and motion capture, or controlling a remote robot that repeats the operator's actions.
In the first-person perspective the person looks from the position of localizing himself within the borders of his own body. In the third-person perspective (3PP) subject's perception occurs from the position of localizing oneself in space outside the boundaries of one's own body, for example, when subjects see himself reflected in a mirror.
The first-person perspective (1PP) facilitates the transfer of information between visual and motor systems due to direct coincidence in measurement between the body image and the corresponding representation of an action. The result of this coincidence is expressed in faster and more accurate subject's reactions [1]. Changing the perspective has negative effects on memory [2,3] and the intensity of emotional reactions decrease [4], the initiation and execution of an action slow down, its accuracy also decreases [5,6]. These changes are associated with a change in the localization of a subject and, as a result, cause several mismatches in the regulation of the execution of an action. There is a conflict between the motor program and visual reafferentation [7]. Some researchers have proposed the presence of two levels of regulation when the perspective changes [8][9][10]. Level 1 is associated with the automatic calculation of the perspective-at what angle the other person looks and what area of the visual scene he sees. The priority of perception from the first-person perspective at this level was not found [10] suggesting that the lability of perception of perspective is necessary for social orientation. For example, the performance of an action by another person causes a spontaneous change in the perspective [11], that is, perspective taking is influenced by the attribution of intentions to others [12]. Level 2 is associated with the explicit stimuli discrimination from a third perspective [8] and the priority of the first-person perspective is manifested at this level.
The self-perception from the third-person perspective is also referred to as an out-of-body experience or disembodiment [13]. This phenomenon has been investigated through the sensory conflict [14], but attributing authorship of movements also affects the ability of identification [15]. For example, a study [16] found that a conflict between the performance of a movement and its visual perception results in the feeling of authorship (or agency) of the action and ownership (or embodiment) of the body decreases.
Another conflict in the perception of one's own actions from the 3PP arises between the proprioceptive and visual perception of action [17]. Numerous studies have been conducted using lenses that cause a mismatch between the actual hand position and its visual perception [18,19]. However, in these experimental models, the subject remains in the same localization inside the borders of his own body and therefore, following a small number of attempts, the impaired coordination of movement successfully restores. In the 3PP, the self-localization as a source of activity is changed. A few studies analyzed the accuracy and temporal parameters of movement when the subject performed the actions from the 3PP [5,6] and, as far as we know, an analysis of the kinematics was not previously conducted.
Perception of body parts in space is defined as body schema. Electroencephalographic source localization studies show that changes in body schema through the third-person perspective is associated with the activation of right temporo-parietal junction [20] and theta-burst magnetic stimulation of this region results in facilitation of the perspective changes [21]. Easier changes of the perspective, from first to third-person view, are also obtained in subjects with higher heartbeat perception [22], in subjects of Western culture and in women [23].
Theoretical frameworks that explain the change in motor control associated with altered body schema in third person point of view are as follows.
Reinforcement learning account suggests that action control is based on the prediction of long-run future consequences, such that motor control is aimed at maximizing rewards and minimizing negative outcomes. The dopamine neuromodulator provides basal ganglia target structures with phasic signals that convey a reward prediction error, or difference between the real consequences of action and the planned results, that can influence learning and action selection [24].
In motor control theory [19,25,26], the inner motor model includes two models, an inverse model and a forward model. Inverse models transform desired goals into a plan to accomplish them. To learn an inverse model, one needs to evaluate the consequences of action, which may be sensed with delays and noise. So, the brain has developed the predictions, which can be achieved by using forward models that simulate the outcomes of a given plan. Forward models are used to give instantaneous predicted feedback that provides an estimate of the state of the controlled effector, and thus to overcome the significant delays of real sensory feedback. When a real sensory feedback does arrive, it can be combined with such predicted feedback to compensate for limitations and the noise of the sensory systems. Thus, forward models are used to generate sensory error signals (predicted feedback minus real feedback), which can guide learning of inverse models. The other proposed role for the forward models involves anticipating and cancelling the sensory effects of self-initiated actions from the incoming sensory stimuli.
According to the predictive coding account [27], brain develops a prediction model about sensory inputs, trying to maximize model evidence and to suppress the deviation from this model, defined as a prediction error or a surprise. An action depends vicariously on sensory states so that sensory prediction errors generate motor command signals and predicts an intimate anatomical relationship between primary motor and sensory systems. On the other hand, an action suppresses sensory prediction by changing the motion of sensory states so that they conform to conditional expectations. This formulation suggests that motor control may not be the selection of an action but an emergent property of the predictive coding.
Studies of perspectives of perception often use static images of other people [11] or parts of their body [1,6,12,17], as well as avatars [4,[8][9][10]28], and do not pay attention to studying the regulation of actions when the perspective of perception is being changed. On the other hand, studies of the perception of one's own actions [18,[29][30][31][32] do not include the perception from a third-person view. Jeannerod [15] has shown that the perception of one's own actions (that is, the correspondence between the motor program and the visual reaffirmation) is an independent self-awareness factor, but this study has not analyzed the kinematics of movements, but only a subjective assessment of an identity. In the current study, we investigated the kinematics of the movement of throwing darts in various conditions of visual perception. The goal of the game of Darts is to hit a spot in the central region of the target (bull's eye). A typical sequence of events consists of aiming, swing, acceleration, release of the dart and completion of the throw/getting feedback about the result. During the performing of dart throws, we recorded the position and speed of the hand by using motion capture sensors. In the experiment the subjects performed dart throws in the first and third-person point of view conditions. To simulate the perception from the 3PP, a video feed from the camera, installed behind and above the subject, was directed into a head-mounted display (HMD), as a result, the subjects directly perceived themselves and their actions from the outside perspective. Thus, unlike previous studies that used a mental rotation to model the perception from the third-person view, and analyzed the response time as well as accuracy to assess the difference between perspectives [1,6,[8][9][10]12,17,28], in this study we used a motion capture of subject's movement while he perceived himself from the 3PP. Such a research paradigm allows separating the subject's body and the localization from which visual perception is carried out and to study the regulation of movement in this condition. In healthy subjects, the border between the unrecognized changes in the angle, induced automatic motor correction, aware of changes of the angle, and evoked consciously controlled movement corrections, lies around 14-15 degrees [33,34]. In the current study, the camera angle was equal and greater than 20 degrees, which should have caused the subjects to activate the mechanisms of the consciously controlled correction of the hand trajectory when performing dart throws, accompanied by a decrease in their identity with their own body.
We expected that the third-person perspective would evoke a decrease in the accuracy of actions, compared with the 1PP condition, in accordance with the data of Watanabe and Higuchi [6]. In accordance with the data from Gorisse et al. [19], we expected the decrease in the amplitude and speed parameters of the movement performance in the third-person perspective condition compared with the 1PP condition.

Subjects
The subjects were 31 students and staff of the Far Eastern Federal University. The data of three subjects were removed due to technical errors during data registration. The final number of subjects was ). Subjects had no or little (few times in their lives) experiences in playing darts and no sports activities addressed accuracy in motion (shooting, throwing, cybersport or others). All participants were volunteers. Subjects have no neurological or mental abnormalities according to the self-report. They did not consume alcohol 24 h before the study and tonic beverages three hours before the study. All subjects were right-handed because in the 3PP condition we changed the camera's location to the right. The study was conducted in accordance with the Helsinki Declaration and was approved by the Ethics Committee of the Far Eastern Federal University. All subjects signed an informed consent.

Procedure
Upon arrival at the laboratory, subjects completed an informed consent. Then they performed 10 training dart throws. After that, they put on a Perception Neuron 32 suit to capture the movement. The suit version contains the following sensors: lower back, chest, left and right shoulder, right arm, right forearm, right hand and each finger of the right hand. This set of sensors made it possible to receive data from all parts of the limb participating in the throwing. However, finger movement data had to be excluded from the analysis due to insufficient equipment accuracy. The sampling rate was 120 Hz. The motion capture suit was connected to the computer via a Wi-Fi network. The computer running the application had an Intel Core I9-9700X @ 3.30GHz CPU, 64 Gb RAM and a Nvidia GeForce RTX 2080 Ti GPU.
After the calibration of the motion capture suit, the subjects were instructed on the rules for throwing and asked to put their feet on the pre-marked lines on the floor. The purpose of these lines was to keep all the subjects in the same position throughout the experiment.
The dartboard, 450 mm in diameter, consisted of concentric black and white rings with a score from 1 on the periphery to 10 in the center, as well as radial sections clockwise from 1 to 36 of 10 • . The dartboard was placed at a 2.37 m distance and its center was at a height of 1.73 m in accordance with the rules of the World Darts Federation ( [35]; Figure 1A). The plastic darts had a metal tip, the weight of the dart was 16.5 g. playing darts and no sports activities addressed accuracy in motion (shooting, throwing, cybersport or others). All participants were volunteers. Subjects have no neurological or mental abnormalities according to the self-report. They did not consume alcohol 24 hours before the study and tonic beverages three hours before the study. All subjects were right-handed because in the 3PP condition we changed the camera's location to the right. The study was conducted in accordance with the Helsinki Declaration and was approved by the Ethics Committee of the Far Eastern Federal University. All subjects signed an informed consent.

Procedure
Upon arrival at the laboratory, subjects completed an informed consent. Then they performed 10 training dart throws. After that, they put on a Perception Neuron 32 suit to capture the movement. The suit version contains the following sensors: lower back, chest, left and right shoulder, right arm, right forearm, right hand and each finger of the right hand. This set of sensors made it possible to receive data from all parts of the limb participating in the throwing. However, finger movement data had to be excluded from the analysis due to insufficient equipment accuracy. The sampling rate was 120 Hz. The motion capture suit was connected to the computer via a Wi-Fi network. The computer running the application had an Intel Core I9-9700X @ 3.30GHz CPU, 64 Gb RAM and a Nvidia GeForce RTX 2080 Ti GPU.
After the calibration of the motion capture suit, the subjects were instructed on the rules for throwing and asked to put their feet on the pre-marked lines on the floor. The purpose of these lines was to keep all the subjects in the same position throughout the experiment.
The dartboard, 450 mm in diameter, consisted of concentric black and white rings with a score from 1 on the periphery to 10 in the center, as well as radial sections clockwise from 1 to 36 of 10°. The dartboard was placed at a 2.37 m distance and its center was at a height of 1.73 meters in accordance with the rules of the World Darts Federation ( [35]; Figure 1A). The plastic darts had a metal tip, the weight of the dart was 16.5 grams.
Subjects performed throws with their leading right hand. The accuracy of the hits was recorded in accordance with the dartboard rings in the range from 1 to 10, as well as a radial position from 1 to 36. The missed throws were scored as zeroes. Method of the study. Subjects wore the motion capture suit and threw the darts from the first and the 3PPs. A. dartboard location relative to the subject, the insert shows the dartboard with the radial sector and radial sector marker. B. The relative to the subject location of the camera used to simulate perception from a 3PP. The insert shows the image taken from a virtual reality (VR) headset when the subject threw the darts in a third-person perspective with a camera placed at a 40° angle position.
Participants were asked to throw darts at the target in four conditions-from the first-person perspective and from the 3PPs with the camera moved on 0°, 20° and 40° to the right relative to the direction of the throw. The 1PP condition was performed first. Then, three conditions with a 3PP Figure 1. Method of the study. Subjects wore the motion capture suit and threw the darts from the first and the 3PPs. (A) dartboard location relative to the subject, the insert shows the dartboard with the radial sector and radial sector marker. (B) The relative to the subject location of the camera used to simulate perception from a 3PP. The insert shows the image taken from a virtual reality (VR) headset when the subject threw the darts in a third-person perspective with a camera placed at a 40 • angle position. Subjects performed throws with their leading right hand. The accuracy of the hits was recorded in accordance with the dartboard rings in the range from 1 to 10, as well as a radial position from 1 to 36. The missed throws were scored as zeroes.
Participants were asked to throw darts at the target in four conditions-from the first-person perspective and from the 3PPs with the camera moved on 0 • , 20 • and 40 • to the right relative to the direction of the throw. The 1PP condition was performed first. Then, three conditions with a 3PP were given for each participant in random order, without a gradual increase or decrease in the angle of perspective. In each of the four conditions, subjects performed 40 throws of five darts per series. After each throw, the first experimenter announced the accuracy of the throw and the radial sector and the second experimenter registered it. After every five throws, the first experimenter cleared the dartboard of darts. In total, every subject had to perform 160 throws.
To simulate the 1PP, the built-in HTC Vive Pro HMD frontal cameras were used. To simulate the 3PP, we used a projection of a video feed from an external high definition wide-angle USB-camera Genius WideCam F100 into the VR HMD. The camera was located behind the subject at a distance of 1.5 m and about 20 cm higher than the subject's height, producing the vertical viewing angle deviation of about 5 degrees. The location and direction of the camera were chosen so that the subject could see the target, his own body down to the waist and the trajectory of the arm during the throws ( Figure 1B). In the current experiment, the 3PP was presented in three different by the angle of the camera conditions. The camera location strictly behind the subjects (zero degrees' condition, 3PP0) created the condition of the 3PP without the distortion of the horizontal perspective angle. Moving the camera at 20 and 40 degrees (3PP20, 3PP40) to the right created the increased 3PP angle of perception.

Accuracy Analysis
Analysis of the accuracy of hits was carried out for each condition (1PP, 3PP0, 3PP20 and 3PP40) and only for throws that hit the target.
The hits were registered in the polar coordinate system and then were transformed to the Cartesian coordinate system where 1 radial section was equal to 10 • and 1 dartboard ring had a thickness of 22 mm (except for the 10-point outer ring, which had 44 mm thickness). The calculation was carried out in accordance with the formulas: x = r × cosϕ, y = r × sinϕ, where x and y are the Cartesian coordinates, r-target ring, ϕ-radial section.
For each subject in each condition, the average absolute accuracy and relative accuracy in millimeters along the OX and OY axes in the Cartesian coordinate system and the number of hits were calculated. Absolute accuracy was calculated as the mean distance from the center of the dartboard. Relative accuracy was calculated as the standard error of the mean (SEM) accuracy.

Kinematics Analysis
For the analysis of kinematics, the right-hand sensor was selected, as well as a sensor from the sternum of the spine. All motion recordings contained some level of noise, which is a high-frequency change in the signal that is not caused by the movement of the subject. The presence of the high-frequency noise made the acceleration analysis difficult, so, we filtered the signal. Figure 2A shows the raw displacement signals with the presence of high-frequency noise and smoothed filtered signal. Figure 2B shows the hand acceleration in the same period on movement.
The displacement of the right hand along the OX, OY and OZ axes and the sensor quaternion of the torso around the OZ axis, described the rotation of the body, were exported to MATLAB 2017b. Then, we used a moving-average filter with a window width of 10 points to remove the high-frequency noise from the data. The velocity of movement was calculated as the first time derivative for each axis. The acceleration of movement was calculated as the second time derivative for each axis. For each condition, the maximum velocity of the hand was identified along the OY axis, that is, perpendicular to the axis of the body and in the direction of the throw. This parameter was chosen because it had a clearly defined peak, which reflects the event of releasing a dart [36]. Other researchers describe the difference in peak velocity and dart release at 2-11 ms [37], which corresponds to about 1 frame of a mocap suit recording. Peaks were identified using the built-in findpeaks function. Then the movements were analyzed in according with the perspective conditions: from the 1PP and of 0 • , 20 • and 40 • from the 3PP. Next, the data were cut into segments from −1.5 to +1 s relative to the moment of peak velocity of the hand. millimeters along the OX and OY axes in the Cartesian coordinate system and the number of hits were calculated. Absolute accuracy was calculated as the mean distance from the center of the dartboard. Relative accuracy was calculated as the standard error of the mean (SEM) accuracy.

Kinematics Analysis
For the analysis of kinematics, the right-hand sensor was selected, as well as a sensor from the sternum of the spine. All motion recordings contained some level of noise, which is a high-frequency change in the signal that is not caused by the movement of the subject. The presence of the highfrequency noise made the acceleration analysis difficult, so, we filtered the signal. Figure 2A shows the raw displacement signals with the presence of high-frequency noise and smoothed filtered signal. Figure 2B shows the hand acceleration in the same period on movement.  To analyze the kinematics, we used data on the displacement, velocity and acceleration of the right hand along the OX, OY and OZ axes. The data of the body rotation around its OZ axis throughout the dart-throwing was analyzed using quaternion. Additionally, we calculated the angle of the hand movement in the period of throwing. For this, we took 12 points (or 0.1 s of the registration time) in the OX and OY axes of hand movement preceding the time point of peak velocity of the hand along the OY axis. In that period, participant's hand moved more or less linearly from backward move point to the dart release point. Later points, followed dart release, were not affect the dart flying angle and were not used in the analysis. The angle was calculated in every two neighboring time points according to formula Angle = arctan x2−x1 y2−y1 , where x 2 , y 2 -the position of the hand along the axes OX and OY at one moment in time, x 1 , y 1 -the position of the hand along the axes OX and OY at the previous moment in time.
All throwing movements that did not result in a goal hit were excluded from the analysis. The trajectories were averaged for each subject in each condition: 1PP (1PP), third-person perspectives in 0 • condition (3PP0), 20 • condition (3PP20) and 40 • condition (3PP40).

Statistical Analysis
For the statistical analysis of the differences in the number of hits between conditions a repeated measurements ANOVA with the factor condition (1PP, 3PP0, 3PP20 and 3PP40) was used. Student's t-test for paired-samples was used to analyze paired differences in number of hits between conditions. Analysis of hits accuracy was conducted in three variants. Firstly, one-sample Student's t-test was used for analyzing the deviance of mean hit accuracy from zero in axes OX and OY in each condition. Secondly, repeated measurements ANOVA with throw conditions (1PP, 3PP0, 3PP20 and 3PP40) and axes (OX and OY) was used to analyze the effects of condition on absolute accuracy. Student's t-test for paired-sample t-test was used to analyze paired differences. Third, two-sample F-test was used to check the difference in relative accuracy between each pair of conditions. Effect sizes of significant results are reported as proportion of explained variance (partial eta squared, η 2 p ). In case the assumption of sphericity was violated, the degrees of freedom for all ANOVAs were corrected by Greenhouse-Geisser epsilon (ε) and Bonferroni corrections were applied to correct the α-levels.
Statistical analysis of kinematic data was carried out in the SPM1d package [38,39]. This package is designed for the analysis of kinematics on the basis of scripts for the analysis of three-dimensional tomography results in the SPM package. It uses random field theory (RFT), which is charged with solving the problem of multiple comparisons. Random field theory is superior to other correction methods since it conducts inference based on the height and the size of connected clusters that remain following the suitably high SPM{t} thresholding (e.g., t > 3.0). Precise probability computations additionally depend on field smoothness and search space morphology. A key point is that a large suprathreshold cluster is the topological equivalent of a large univariate t-value.
So, SPM1d allows analyzing trajectories for the entire duration of the movement. It also provides an opportunity to make corrections for multiple comparisons (familywise error rate, FWER). Since the research is exploratory, we carried out an analysis of the long-term area of the action, without breaking it up into separate periods of analysis. This raises the threshold for familywise error correction (FWEC), but the results are more resistant to accepting false alarms. In the statistical analysis, an interval from −1.5 to 0.5 s relative to the time of the maximum throw speed was used, and it included all phases of the throw: raising the hand, backward move, acceleration, throwing and follow-through.
A repeated measurement ANOVA, involving four throw categories (1PP, 3PP0, 3PP20 and 3PP40), was used to analyze the effects. The significance level was calculated using permutation statistics; the number of permutations was 1000. The FWER adjustment was used to account for multiple comparisons. Paired differences were evaluated using Student's t-test (with FWER correction). Regression analysis was used to study the prediction of throw accuracy based on kinematics data.
The significance level was p < 0.05.

Accuracy Analysis
Analysis of accuracy was carried out on the data of number of throws and mean hit accuracy in each condition.

Target Hit Accuracy
One-way ANOVA of the number of successful hits reveal the significant effect of Condition (F(3,81) = 30.77, p < 0.001, ε = 0.961, η 2 p = 0.533). The number of hits gradually decreases (Table 1) from 1PP to 3PP0 and 3PP20, but 3PP20 does not differ from 3PP40 (Table 2). Therefore, the number of successful hits is affected by perspective distortion and angle distortion but does not depend on the angle value.

Hit Accuracy
The accuracy of hits of each category is presented in Figure 3 and Table 1. Firstly, we conducted the analysis on differences in mean hit accuracy between conditions. ANOVA was calculated with the factors condition (1PP, 3PP0, 3PP20 and 3PP40) and axis (OX and OY). Results revealed significant effects of condition (F(3,81  A statistical analysis of pairwise differences in the number of successful hits, average absolute accuracy values along the OX and OY axes and equality of variances of successful hits along the OX and OY axes are presented in Table 2. Additionally, we analyzed the deviation hit accuracy from the OX and OY axes using onesample t-tests. The results indicate that conditions with a natural perspective angle (1PP and 3PP0) show a significant bias for hitting to the left side of the target and conditions with a changed perspective angle (3PP20 and 3PP40) shows a significant bias for hitting to the right side of the target ( Table 1). The absolute accuracy of hits along the OY axis showed that in the 1PP the deviation was non-significant and in 3PP conditions hits were in the lower part of the dartboard. Thus, the absolute accuracy along the OX axis was affected by the parameter of distortion of degree and the absolute accuracy along the OY axis was affected by the parameter of distortion of perspective. A statistical analysis of pairwise differences in the number of successful hits, average absolute accuracy values along the OX and OY axes and equality of variances of successful hits along the OX and OY axes are presented in Table 2.
Additionally, we analyzed the deviation hit accuracy from the OX and OY axes using one-sample t-tests. The results indicate that conditions with a natural perspective angle (1PP and 3PP0) show a significant bias for hitting to the left side of the target and conditions with a changed perspective angle (3PP20 and 3PP40) shows a significant bias for hitting to the right side of the target ( Table 1). The absolute accuracy of hits along the OY axis showed that in the 1PP the deviation was non-significant and in 3PP conditions hits were in the lower part of the dartboard. Thus, the absolute accuracy along the OX axis was affected by the parameter of distortion of degree and the absolute accuracy along the OY axis was affected by the parameter of distortion of perspective.
Secondly, we analyzed the relative differences between the conditions. The relative accuracy along the axis OX revealed the statistically significant difference in all pairs, associated with 1PP, and did not reveal a statistically significant difference in all other pairs. Relative accuracy along the OY axis did not reveal statistically significant differences in all pairs of conditions. Therefore, change in perspective from 1PP to 3PP resulted in a decrease in the total number of successful hits, absolute accuracy along the vertical axis towards the bottom of the dartboard, and a decrease in relative accuracy along the horizontal axis. Change in the angle of perception in 3PP resulted in additional decrease in the total number of successful hits, and absolute accuracy along the horizontal axis was shifted towards the right side of the dartboard. In other words, we had 3 groups (1PP, 3PP0 and 3PP20 with 3PP40) that are statistically significantly different in terms of the number of Brain Sci. 2020, 10, 55 9 of 21 successful throws (N) and the absolute accuracy of hits along the OX and OY axes. These conditions can be designated as a condition with a natural perspective and a natural angle (1PP), a condition with a distorted perspective and a natural angle (3PP0) and a condition with a distorted perspective and a distorted angle (3PP20 and 3PP40). Control analysis was performed to investigate the sex differences in the number of hits and mean accuracy. Power analysis with the goal power equal to 0.9 and the alpha equal to 0.05 for the given total standard deviation and condition's means reveal that for the number of hits required 12 subjects, for the hit success along the OX axis required 11 subjects and for the hit success along the OY axis required 13 subjects. This is more than two times less than in the current study.

Kinematic Analysis
The analysis of kinematic data was carried out for the successful throws in each condition using the displacement, velocity and acceleration of the right hand as well as rotation angle of the torso and displacement angle in the period of a throw. Figure 3B shows the trajectories of the right hand movement (positioned in three-dimensional space) when darts were thrown from the 1PP and the 3PP with 0 • , 20 • and 40 • angles of perspective distortion. The mean values of hand displacement significantly differed when the perspective changed, the path of hand displacement become less amplitude along the axis of the throw in backward move period and less downward move in the follow-through period, relative to the normal 1PP. The displacement data along the OX axis did not produce statistically significant effects and were not reported.

OY axis Displacement
The throwing condition (1PP, 3PP0, 3PP20 and 3PP40) produced a significant effect on the hand movement ( Figure 4A) in the period from −0.298 to −0.099 s ( Figure 4B).
Pairwise comparisons showed (Supplementary Materials Figure S4) that right hand displacement was more negative in 1PP in comparison with 3PP20 (from −0.265 to −0.116 s) and 3PP40 (from −0.257 to −0.158 s) conditions. There were also almost significant differences in movement in the similar period in 3PP0 condition compared to 1PP condition. The 3PP conditions were not differ from each other.

Velocity
Significant effects of the throw conditions ( Figure 4C) in the periods from −0.149 to 0.074 s were obtained ( Figure 4D). Pairwise comparisons showed that the velocity in 1PP condition was higher compared to 3PP0 (from −0.133 to −0.066 s and from 0.041 s to 0.066 s), 3PP20 (from −0.133 to 0.075 s) and 3PP40 (from −0.142 to −0.05 s) conditions. The 3PP conditions did not differ from each other.

Acceleration
The significant effects of the throw conditions ( Figure 4E) in the periods from −0.217 to −0.108 s were obtained ( Figure 4F). Pairwise comparisons showed that during the period of backward move and retraction of the right hand, the hand acceleration in 1PP condition was higher compared to 3PP0 (from −0.167 to −0.125 s), 3PP20 (from −0.192 to −0.117 s) and 3PP40 (from −0.192 to −0.125 s) conditions. The 3PP conditions did not differ from each other.  These results indicate that the hand kinematics in the 1PP condition had lower amplitude and was smoother in the period from the backward move to the time after the peak velocity. These results indicate that the hand kinematics in the 1PP condition had lower amplitude and was smoother in the period from the backward move to the time after the peak velocity.

Displacement
Significant effects of the right hand displacement were found in periods from 0.166 to 0.689 s ( Figure 5A,B). Pairwise comparisons showed that the hand displacement was higher in the 1PP condition as compared to 3PP0 condition (from 0.174 to 0.697 s), 3PP20 condition (from 0.216 to 0.647 s) and 3PP40 condition (from 0.348 to 0.539 s). The 3PP conditions did not differ from each other.

Velocity
The significant effects of the throw conditions ( Figure 5C) in the periods from 0.116 to 0.233 s were obtained ( Figure 5D). Pairwise comparisons showed that during the period of lowering the hand down after throwing a dart, the hand velocity in 1PP condition was higher compared to 3PP0 (from 0.142 to 0.208 s), 3PP20 (from 0.166 to 0.258 s) and 3PP40 (in the period from 0.133 to 0.192 s) conditions. The 3PP conditions did not differ from each other. Pairwise comparisons showed that the hand displacement was higher in the 1PP condition as compared to 3PP0 condition (from 0.174 to 0.697 s), 3PP20 condition (from 0.216 to 0.647 s) and 3PP40 condition (from 0.348 to 0.539 s). The 3PP conditions did not differ from each other.

Velocity
The significant effects of the throw conditions ( Figure 5C) in the periods from 0.116 to 0.233 s were obtained ( Figure 5D). Pairwise comparisons showed that during the period of lowering the hand down after throwing a dart, the hand velocity in 1PP condition was higher compared to 3PP0 (from 0.142 to 0.208 s), 3PP20 (from 0.166 to 0.258 s) and 3PP40 (in the period from 0.133 to 0.192 s) conditions. The 3PP conditions did not differ from each other.

Acceleration
Acceleration of right hand movement had non-significant effects of throwing conditions ( Figure 5E,F).
Thus, the subjects lowered their right hand after the throw with the greater amplitude and velocity in the 1PP compared to the conditions with the distorted perspective.

Torso Rotation
To study the rotation of the body during a throw, a torso quaternion around the OZ axis was used. The significant effects of the throw conditions ( Figure 6A) in the periods from −1.5 to 0.183 s ( Figure 6B) were found.
Pairwise comparisons showed that the subject's torso was turned more leftward (counterclockwise) during periods of raising the arm, moving backward and throwing in the 1PP condition compared to 3PP0 (from −1.5 to −1.283 s and in the period from −0.1 to 0.067 s), 3PP20 (from −1.5 to 0.075 s) and 3PP40 (from −1.5 to 0.05 s) conditions. Thus, the throw in the 1PP was accompanied by a more natural torso rotation counterclockwise, which makes it more convenient to position the right hand concerning the target.

The Movement Angle during a Throw
Dart accuracy significantly depends on the hand position in space during dart release time [18], and the dart release occurs several milliseconds before the peak velocity [37]. So, the direction of the hand movement in a short period immediately before and in time of the peak velocity includes the dart release time and should affect hit accuracy. In the present experiment, the hand movement direction was represented as the angle between the direction of motion and the OX axis in the XY plane.
The significant effects of the throw conditions ( Figure 6B) in the periods from −0.058 to 0 s were obtained ( Figure 6D). Pairwise comparisons showed that at the time of throwing the dart, the angle of the direction of hand movement was significantly greater in the 3PP condition at 20 degrees (from −0.058 to 0) and 40 degrees (from −0.05 to −0.008 s) relative to the 1PP condition.
Thus, the change from the first to the 3PP results in shifting the torso direction to the right and increasing in the angle of hand movement immediately before and at a time of dart release.

Effect of Kinematic on Accuracy
It was previously described that conditions affect the absolute accuracy along the OX axis, however, they did not affect the hand movement. In this section we presented the results of regression analysis, predicting hit accuracy from kinematic data.
Brain Sci. 2020, 10, 55 13 of 21 increasing in the angle of hand movement immediately before and at a time of dart release.

Effect of Kinematic on Accuracy
It was previously described that conditions affect the absolute accuracy along the OX axis, however, they did not affect the hand movement. In this section we presented the results of regression analysis, predicting hit accuracy from kinematic data.  The regression analysis did not reveal statistically significant effects of displacement, speed, acceleration along the OX and OY axes and torso rotation angle on the absolute accuracy of hitting along the OX and OY axes. However, an angle of the movement during the throws predicted the absolute accuracy along the horizontal axis (F = 2.38, p = 0.049) in 1PP conditions at time −0.050 s. Further, we analyzed the relative data. The analysis included the differences between 3PP20 and 1PP as well as between 3PP40 and 1PP in hand movement angle and accuracy gain along the OX axis between the corresponding conditions since these variables had significant differences between conditions. The angle data differed significantly from the normal distribution, so we used a non-parametric Spearman correlation. The analysis was carried out in 12 points before the time of peak velocity, i.e., from −0.100 to 0 ms. For the difference between 3PP20 and 1PP it was found significant correlations between angle difference and hit gain from −0.042 to 0 c (p < 0.048) with maximum correlation is −0.017 c (R = 0.57, p = 0.002). For the difference between 3PP40 and 1PP it was found significant correlations between angle difference and hit gain from −0.083 to 0 c (p < 0.049) with maximum correlation is −0.050 c (R = 0.66, p < 0.001).
Power analysis calculated for the point of maximum effect of movement angle with the goal power equal to 0.9 and the alpha equal to 0.05 revealed that for the given total standard deviation and condition's means the study required six subjects. The required sample sizes for other variables were greater than in the present study.

Discussion
The present study revealed the changes in accuracy and hand kinematic while the subjects performed dart throws perceiving themselves from 1PP and from the 3PP with various degrees of perception. The results of the experiment showed that in the 1PP condition the number of successful hits decreased and the mean accuracy of the hits shifted downward compared with the 3PP conditions. Shifting the angle of self-perception in the 3PP rightward results in shifting mean accuracy in the same direction. Kinematic analysis revealed that in the 1PP condition displacement speed and acceleration of the right hand in the direction to the target in the period from a backward move to the time of maximum velocity were greater compared with 3PP. In the follow-through period amplitude and velocity of the lowering the hand was greater in the 1PP condition compared with 3PP condition. Finally, the torso angle was greater in the 1PP condition compared with 3PP condition and hand movement angle before the time of peak velocity was smaller in the 1PP condition compared with 20 and 40 degrees of the 3PP condition.
The motor program essentially depends on the visual feedback-reafferentation [7], which in turn is associated with the perception of acting subject's localization. Studies [17,18,32] showed that the subject's own actions affect the effectiveness of mental rotation in the way of reducing interference in the perception of subject's hand from 1PP. Another study suggests that changing the perspective reduces the speed and accuracy of movements [4], which was confirmed by the results of this study. The angle of a virtual avatar [28] and one's own body [9] influence perception accuracy when changing the perspective of perception-the congruent position of the stimulus or avatar compared to the position of the subject's own body facilitates perception.
In the present study, subjects performed dart throws from the 1PP in a situation of congruence of visual and proprioceptive afferentation, and from a 3PP in a situation of conflict between visual and proprioceptive information. The amount of conflict was increased by increasing the angle of the self-perception from the 3PP from 0 to 20 and 40 degrees.
The number of successful hits decreased gradually from 1PP to 3PP0 and to 3PP20 and stabilized at 40 degrees. So, changing the angle from 1PP condition to 3PP0 condition was about 5 degrees above the view. According to data [33,34] the border for automatic movement regulation was 14-15 degrees. In the present experiment shifting the angle from 1PP to 3PP with zero degrees was under this border. The angle of view was also not shifted laterally, Level 1 of regulation [8][9][10] should not be affected and the target was clearly visible in front of subject view. However, change in perspective of view in the present experimental results in a decrease in movement success. These results, in according with similar reports [5,6], showed a decrease in accuracy in 3PP condition. However, in report by Watanabe R. and Higuchi [6] was angle rotation of 180 degrees, but in the report by Gorisse et al., [5] was zero degrees' rotation, so, it is unclear the relative contribution of the 3PP condition and rotation angle.
The results of the current study shed light on this topic. Particularly, increase the lateral angle in the 3PP from 0 to 20 and 40 degrees induced an additional decrease in the number of hits. The source of this decrease lay in controlled motor regulation i.e., angle changed with extend exceeding the border of controlled regulation [33,34] and should involve the Level 2 regulation, which is associated with the limited capacity of the working memory [8].
Shifting in perspective from 1PP to 3PP0 results in shifting the mean accuracy downward, i.e., in the opposite direction. However, shifting the perspective angle rightward from 3PP0 to 3PP20 and 3PP40 caused shifting the mean accuracy also in rightward, i.e., in the same direction. Thus, in the present study was found the dissociation between the accuracy along horizontal and vertical axes. Orthogonal changes assume different mechanisms. Vertical axis associated with overcoming gravity, thus, requires muscle effort. Throwing to the greater distance required the greater muscle effort for giving more impetus for higher and longer flying of the object. The effect of the third perspective, but not the horizontal angle, expressed in reducing the hit's relative accuracy. Changes in muscle effort could be produced by the illusory change in the estimation of the distance and self-body height. In the present experiment, the location of the camera was backward and higher than the participant's eyes position and viewing from this reference frame may evoke the illusion. Alternatively, perceiving one self's body may increase attention to the movement or inner focus of the attention [40]. It is also known that the inner focus of attention decreases the accuracy in dart hitting [41].
Changes in the horizontal axis required only a shift in movement accuracy. However, this does not explain why the mean accuracy of the hits shifted in the congruent direction with the perspective angle. A possible reason for this may lay in the perception of target location. When the perspective is shifted to the right in the 3PP, the subjects perceive the target in between the self-body and actual viewpoint, i.e., illusory shifted rightward. Implying that the motor program also shifts the direction of the movement rightward.
Changing the angle of view is studied with the help of lenses and results in the gradual recovery of motor regulation [18]. Changing the perspective also has a negative effect on the movement accuracy [5,9,10,28]. In the current experiment, we found that perspective and angle have a different impact on the hit accuracy of the dart throwing. Changing perspective by viewing oneself from back and up shifts the reference frame, resulting in a decreased number of hits, decreased horizontal relative accuracy, shifting the mean accuracy of the dart-throwing downward due to the changing the estimation of distance, and self-body height or evoked inner focus of attention. Shifting the angle additionally evoked the controlled mental rotation mechanism with limited working memory capacity results in an additional decrease in the number of hits and shifting mean accuracy in congruent direction due to the illusory shifting the target location.
The accuracy data in the current study are complemented by the kinematic results. Data of [5] revealed the decrease in velocity of actions in the 3PP. In the current study, the analysis of the trajectory and velocity of the right hand suggested that subjects perform hand movements in 3PP condition with lower amplitude during the backward move period and lower speed and acceleration immediately before the peak velocity. These data are consistent with the action constraint hypothesis [42] because the subjects were seeing their own hand in the 3PP condition, their inner focus of attention [40] was increased, and they tried to reduce the conflict between the perception of their hand from the outside and the need to complete the motor program, which also attracted attention to the process of executing the movement.
The difference between the 1PP and 3PP conditions in terms of displacement, speed, and acceleration significantly overlap in time and are located in the period −200 to −100 ms. In studies [29,31,43], it was found that motion correction when changing the location of the target during movement occurs after 115-147 ms due to a mismatch of proprioceptive data with the forward model. However, unlike previous studies using a change in the position of the target during the movement of the hand, in the present study the position of the target remained constant, only the angle of perception of oneself and the target are changed. Therefore, we assumed that the visual control of movement when perceiving oneself from a third-person perspective is increased due to a mismatch between visual and proprioceptive perception. Higher control of movement in turn causes a decrease in the amplitude and dynamic characteristics of its implementation. In other words, approximately 100-200 ms before the release of the dart, subjects try to control the hand to resolve the conflict between the visual and proprioceptive systems. The data are consistent with the results of [44], which showed that the accuracy of the throws is positively related to the peak of acceleration of the hand, activity of posterior deltoid muscle and negatively related to activity of thenar muscle.
Changes in the amplitude and dynamic characteristics of movement in third-person perspective condition can also be caused by changes in the estimate of the distance to the target and the perception of the height of one's own body. Upon an illusory change in the distance [32], independent contributions of the perceptual and motor components to eye movement patterns were found.
A decrease in the amplitude and speed of the throwing hand is also accompanied by a shift of hits downward, however, a decrease in the position of the hand along the OZ axis before the peak velocity does not occur. A downward shift in the accuracy can be associated with a lower speed of the hand that transmits the impulse to the object. Indeed, the speed of the hand in the target's direction was less from the 3PP compared to the 1PP. This, in turn, can be caused by attention to the hand in the condition of performing throws from the third-person perspective. The data [41] indicate that with inner focus of attention to the limb, the muscle activity of the triceps brachii agonist increases when darts are thrown. In a study [45], attention to a limb increases the tension of antagonistic muscles and reduces the effectiveness of the regulation of movement.
Further hand movement becomes faster, and subjects did not have time to perform the movement correction based on the real perceptual feedback [30], so the hand movement executed based on the inverse model and predicted proprioceptive feedback [25]. Thus, amplitude and speed characteristics of the hand movement in the dart release time did not differ between conditions in the current experiment, except velocity along OY axis. Effect of peak velocity at this axis was small and was accompanied by two greater effects before and after peak velocity, i.e., during the hand acceleration and hand slowing.
The second period of differences in hand velocity along OY axis could be induced by two causes. First, in the 1PP condition, the hand moved on a ballistic trajectory with the greater speed and the subject had to make more effort to stop it. In the 1PP condition the hand movement amplitude was greater in the period of the backward move and also tendency to increase in amplitude following dart release ( Figure 4A). Contrastingly, in the 3PP condition, slower hand movement during the dart throwing could result in better hand control and early stopping of the hand. Additionally, reducing the speed of the hand movement in the 3PP condition is evoked by the conflict between visual and proprioceptive information. Perhaps, both hypotheses are true and the first is more applicable for the explanation of the hand movement from the 1PP and the second explains better the movement regulation from the third-person perspective.
Following the dart release, subject's attention is directed to assessing the throw accuracy and drooping hand no longer carries the functional significance for dart throw. However, in the current experiment, we found smaller hand amplitude and velocity along the vertical axis in 3PP condition. A similar effect was found in our previous study [36] in the eyes-closed condition. In the current experiment in the follow-through period subject's attention was rather directed to target for assessing the throw accuracy, than to the fallen hand. Dart flying time plus time of visual and cognitive analysis exceeded the time when differences between hand velocity in the first and 3PP conditions were started. So, the differences between conditions in amplitude and velocity were not evoked by assessing the throwing accuracy but associated with the motor conflict. To the 100-200 ms follow the peak velocity the hand movement occurred with less velocity ( Figure 4C) and motor regulation based on proprioceptive feedback was available. So, the conflict between visual and proprioceptive data become actual again in a condition such as less relaxed biceps muscle and less lowered hand.
As an initial hypothesis of our study, we suppose that shifting the viewpoint in 20 and 40 degrees induced shifting the hand movement in the same direction in order to combine the eye, hand and target in line. However, in this study, we did not find differences in movement, speed or acceleration in the direction of the shift in the angle of perception. The absence of differences along the OX axis could be caused by the fact that, for hitting a relatively small target (10 • 50 ), sufficiently strong restrictions are imposed on the movements to ensure accuracy of hits. Considering that the majority of misses in the third-person perspective conditions were to the right from the target, it can be assumed that a larger target size would catch a larger rightward deviation of hitting caused by stronger deviations of the arm moving in the same direction.
In order to identify the shifting of the body position as a whole and the hand in particular, with an increase in the third-person condition angle, we performed an additional analysis of the subject's body rotation and the hand angle in the XY plane during the throws. We found that in the 1PP condition, the body was turned more leftward, that is, counterclockwise, in the period from −1.5 to 0.183 s and, therefore, the right shoulder and hand were closer to the virtual line connecting the subject's eye and the target. This position most closely matches the ability to control the throw. The perception of oneself behind the third-person, regardless of the angle, leads to a smaller turn of the body leftward and the shoulder becomes more perpendicular to the line of the throw. A smaller turn of the body to the left when performing third-person perspective throws imposes physical limitations on the possibility of motor regulation. It should also be noted that the differences are not related to the different settings of the subjects during the throws. As indicated in the method section, all subjects stood on marks on the floor and their leg position was the same for all subjects in all conditions. Consequently, the differences found concern torso rotation caused by cognitive factors, but not the subjects' physical position.
Since the angle of torso's rotation was greater in the first-person condition compared with the third-person condition from the very beginning of the analysis period, we assumed that the rotation of the torso was associated with proactive motor control and the motor setting, when the movement was performed. It should also be noted that the time of differences between the angles of torso's rotation from the first and 3PPs ends 183 ms after the time of the hand's velocity peak, which corresponds to the time of motion compensation when changing the target's localization [9,33,38]. The influence of the cognitive factor can be traced in the fact that significant differences between the conditions of the first and 3PPs in terms of the angle of torso's rotation end at about the same time period when the amplitude differences of lowering the arm begins. This suggests that proactive motor control ends after the completion of the throw, but the cognitive conflict caused by third-person perception continues to be pronounced and affects the amplitude of movements.
Finally, according to the angle of the hand movement in the XY plane, it was found that the hand moves from right to front. A smaller value of the angle indicates a greater deviation of the hand movement to the right. The results showed a smaller angle of the hand movement in the 1PP condition ( Figure 6C), that is, the hand movement was directed more from right to front (Supplementary Materials Figure S1A). In the third-person perspective condition with a viewing angle of 20 and 40 degrees, the hand moved with a larger angle relative to the OX axis, that is, more straightly towards the target. Differences in direction reach a significant level immediately before and at the time of the peak velocity and overlap in time with differences in speed along the OY axis. These results indicate that the change in the angle of perception in the third-person condition affects the program of movement, which deviates in the opposite direction. These results also correlate with the change in the average accuracy of dart throws. A larger angle of the hand movement's direction from right to forward in the 1PP condition is reflected in the displacement of hits to the left, relative to the direction of hand movement, and a straighter movement of the hand towards the target in 20 and 40 degrees of the third-person perspective conditions is reflected in the displacement of hits to the right. Thus, a change in the angle of perception to the right causes the opposite change in the direction of hand movement, which in turn predicts a shift in the average accuracy of hits, congruent to the shift in the angle of perception. Moreover, the angle of rotation of the torso does not correlate with the displacement of the hit. These results correspond to the data [37,46], which showed the existence of independent parameters of the place and the time of release of the dart, affecting the hit's accuracy. According to [37], the moment of dart release occurs before the time of the peak velocity for 2-11 ms, that is, in the results of this study, the deviation of the hand movement occurs at the time of the release of the dart.
Oppositely directed changes in the angle of perception and the angle of hand movement could be caused by the illusion of a target's displacement. While the subject illusory was seeing the target on the right, to shift the desired hit in the same direction, the subject needed to move his hand until the moment of peak velocity with a lesser shift to the right. Probably, the reference frame was also shifted to the point where the dart was released, so the less the subject was prone to illusion, the greater was the deviation of the hand from the axis of forward movement and the smaller was the deviation of hitting to the right in the third-person condition, compared to the third-person condition. However, a larger increase in the angle of perception did not lead to a larger increase in the angle of hand movement.
Regarding the angle of the perception one could think, that current results were similar to that used the lenses for visually shifting the position of the target [18,30]. However, the subject in these experimental conditions localizes itself in the same place and corrects the movement of the hand under the changed angle of view in order to match the egocentric position. In the third person view condition in the current experiment, the subject locates himself in a different place and adopts the hand movement to a changed perception of the self-location. Thus, the movements are adapted not only in accordance with the sensory flow but also in accordance with the subject's location.
Thus, decreasing the hand amplitude and speed in the 3PP condition could be induced by the conflict between proprioceptive and visual information. As a result, attention is shifted from controlling the accuracy of the throw to the movement regulation. Studies have shown that the inner focus of attention, controls the bodily implementation of the action, reduces the accuracy of the action. In opposite, the external focus of attention, aimed at controlling an object, increases the accuracy of dart throws and reduces muscle tension [41]. In the present study, 3PP condition evoked proactive motor regulation, reflected in less torso rotation. Then the throws were executed with less amplitude of backward move, less velocity and acceleration of the hand before dart release, close to the time of maximum velocity, as well as, less amplitude and speed of hand lowering follow the dart release. These periods were more than 100 ms before and after time of peak velocity and associated with the movement regulation based on both visual and proprioceptive feedback [29,31,43], which is in the conflict in the 3PP condition in the current study. In the period around the peak speed, the hand movements were too fast to be regulated based on the real feedback information. So, the hand movement in a short period around dart release was not affected by the third-person perspective and realized based on both the inverse model and predicted sensory information of the forward model [25]. On this period shifting angle of the movement predicts a rightward shift in the mean accuracy. Since the inverse model was not trained for the movement regulation in changed perceptual condition, the hand kinematic and throw accuracy executed with low prediction error correction and changed significantly. Finally, follow the dart release the influence of proactive motor control disappeared.
The effect of changing the perception angle by 20 • and 40 • to the right on the dart throwing results can manifest itself in a similar way with dysfunction of somato-spatial synthesis while correlating the object's location with the respect to one's body and constructing a corresponding action program. For example, a mismatch of visual and proprioceptive information is observed in patients with optic ataxia associated with a dysfunction of the parieto-occipital junction [47]. Conducting cognitive diagnostics in VR or cognitive rehabilitation in VR by using Vicariation or by restructuring functional systems, without taking into account the factor of perception distortion of the perspective and body proportions, can produce an inadequate assessment on the degree of cognitive dysfunction. Studies have also shown that out-of-body experience [13] and body schema [20,21] are associated with the activity of the right inferior parietal cortex. The perception of oneself from the 3PP in the current study may be due to the activation of these areas of the cortex.
The practical application of the results of this study also may extend to other areas. In the gaming industry, the perception and management of an avatar require a change in the perception perspective. In some areas of industry, there are requirements of online control of robotic actions, based on the operator's movements. In sports or dancing, training often takes place in a hall with mirrors, and the regulation of movements is based on a mirror reflection, that is, from the third-person view.
The present study had several limitations. Firstly, there were technical limitations of the cameras used. HTC VIVE Pro HMD built-in cameras had poor image quality and USB-camera used to simulate third-person perspective provided 2D images. This imposes restrictions on the assessment of the accuracy of hits by the subjects. There was also a slight but noticeable hardware delay when transmitting images from a first-person view camera and a third-person view camera.
Secondly, changes in the kinematics of motion associated with the changes in perspectives can affect different links of the motor chain. Therefore, in addition to analyzing the rotation of the torso and the angle of the direction of movement of the hand, the analysis of the angles and position of the shoulder, arm and forearm will provide additional information and will help to better understand the motor effects of changing perceptual perspectives.
Thirdly, we had not registered the time of dart release and dart flight trajectory. Since the time of dart release and time of the hand peak velocity are close to each other [37], we propose that selection of peak velocity as a reference point reflect the inner nature of this movement, aimed to speed up the dart. However, third-person perspective condition could change the timing between dart release and peak speed.
Fourthly, target height was located on a fixed position for all subjects. Since the height of the subjects was varied, the target was located above the eyes for some subjects and below the eye for other subjects. These differences could affect the hand kinematic. In future research, it would be preferable to set the height of the target at an individual level.
Fifthly, although there were enough participants to make conclusions, but for kinematic, except hand movement angle, G power analysis showed that the number of participants was insufficient.
Finally, in the current experiment, some error throws were outside the target area. In most cases these throws in the 3PP conditions were shifted rightward. So, it seems justified to use the target with larger area in order to catch the throws with large deviation from the center of the target.

Conclusions
In the present study, we investigated the change in accuracy as well as hand and torso movement when making dart throws in the first and third-person perspectives with varying angles. The results indicated that the mean accuracy shifted in the opposite direction in the vertical axis and congruent direction in the horizontal axis. Kinematic data revealed less torso angle in the 3PP conditions before and during the throw. The amplitude, velocity and acceleration in 3PP condition were decreased as compared with 1PP condition before and after the peak velocity and the same variables did not differ between conditions more than 100 ms around peak velocity period. The hand movement angle toward the target direction was smaller in the 3PP conditions with 20 and 40 degrees compared with the 1PP condition just preceding the time of peak velocity and the difference between conditions predicted the changes in mean accuracy of the throws. Thus, the results of the current study revealed that the transformation of the motor program takes into account the subject's localization.


s2fieldsofstudy:
Education
Computer Science

text:
EMPIRICAL OBSERVATION IN THE SEARCH OF STRATEGY FOR DEVELOPMENT OF E-LEARNING: CASE OF NATIONAL UNIVERSITIES IN UZBEKISTAN

Majority of universities in the world are implementing technology enhanced learning in order to improve education and help students to develop learning. Nowadays technology enhanced learning offers universities with all context of education and universities are trying to apply it. One such case is the TARCI (Tashkent Automobile and Road construction institute) in Uzbekistan that is subject of this project. The university’s current system is not reliable; also it is outdated in terms of its structure; and need to be replaced with e-learning system. In thisresearch study using a questionnaire as data collection techniques. This data collection was necessary as none of the interviewed individuals had experience with any e-learning systems. The analysis of the data shows positive attitude students for implementing an elearning system. This proposed system is based on NodeJS and Elgg software and it is believed to be a full scale elearning system that offers courses for students in TARCI. Through user requirements, the project comes up with a reliable e-learning system that will help the TARCI’s administration manage courses and monitor students’ progress. Hence therefore the collaboration between students and staff would be improved with developed e-learning system.

INTRODUCTION
Nowadays, using e-learning system in education is becoming, without doubt, more and more important learning method. E-learning system is being used in universities and in higher education, and also in organizations that look for accurate and continuous formation of their employees. One simple activity of this type of learning is the process of learning evaluation; it means to value the earned knowledge by the students. The evaluation is the movement for the student to verify the reached knowledge in the learning process. In a summary, the evaluation process allows the student to compare the acquired knowledge with the expected one in the formative action and thus to determine if the objectives have been achieved correctly.
The advent of e-learning is mainly due to the widespread use of ICT in education. Today, elearning has its own standards that are developed by Instructional Management System (IMS). E-learning has a Learning Management System (LMS), which consists of the tools for the creation, storage, use, educational content delivery and management in the multiplayer mode. The main thing that makes e-Learning unique is an opportunity of repeatedly usage of once created multimedia educational content, including online access in the real time. User not only observes the creative process of content creation, but also can participate in establishing learning process. E-learning creates educational content around the social networks, forums, and chat rooms.
E-learning allows converting the content of education, improving mobility and creative curricula and programs; it provides the possibility of designing and constructing a variety of tools for building professional competence. More and more universities world over are deploying e-learning system for the sake of improving learning process efficiency and student"s knowledge quality.
Great attention to the higher education in Uzbekistan is paid to the improvement of the educational system and training of qualified specialists. On the basis of the president's decree dated February 28, 1992, twenty-four new institutions of higher learning and their branches to train specialists for principle branches of the national economy were established.
Today there are 61 institutions of higher learning function in the republic, including 16 universities, 39 teacher training institutes, medical, technical, economic, agricultural, and other institutes. About 300 thousand students master 276 specialties there. The oldest higher Institutions in Uzbekistan are the National University named after Ulugbek, the Technical Institute (Polytecnical Institute). Since 1991 the number of higher educational institutions has increased by 30 %. New higher educational institutions have appeared: The University of World Economy and Diplomacy, Academy of State and Public Structuring, Academy of Armed Forces, Academy of Ministry of Internal Affairs. There are also few branches of foreign universities, such as Branch of Lomonosov Moscow state university, Russian University of oil and gas, Singapore university of management and others.
TARCI (Tashkent Automobile and Road Construction Institute) in Central Asia is the only institution of higher education in this area. Institute situated in the center of the capital of Uzbekistan. There are 4000 students who enter the institute every year, to obtain their bachelor's and master's degrees.
The main objective of this study is to explore ways to develop e-learning for national universities in Uzbekistan. Current study also made attempt to seek solutions for problems by answering following questions: 1. What is the current situation with learning process in national universities?
2. Which e-learning model is suitable for Uzbekistan universities?
3. How e-learning can benefit learners, practitioners and educational institutions within Uzbekistan?
In this research it is anticipated to employ a relevant research methodology to analyze the data. Obtained results will lead to suggestions for the development appropriate e-learning model that can benefit students and universities, which would in turn enhance learning process.
The study will concentrate on the e-learning in Uzbekistan universities analyzing e-learning system for Uzbekistan universities. It includes using "nodeJS" and "elgg" as Learning Management System (LMS) to analyze effective online learning web site for national universities.
Basically, there are two main objectives: 1.
Investigate the role of elearning system in education processes; 2.
Determine the current situation of learning process in Uzbekistan universities to determine and analyze suitable e-learning model for the universities.
Also, there is a practical problem, which current study will solve given that Uzbekistan is a country relatively new to e-learning practices. Thus, this research aims to provide a knowledge foundation work that brings following benefits : convenience and portability (reading, uploading, downloading materials at any time), flexibility (use most suitable tools for learning style), elimination geographical barriers to open up broader education options; 24/7 accessibility that makes scheduling easy and allows a greater number of people to attend classes.

SERVQUAL
The SERVQUAL service quality model was developed by a group of American authors, 'Parasu' Parasuraman, Valarie Zeithaml and Len Berry, in 1988. It highlights the main components of high quality service. The SERVQUAL authors originally identified ten elements of service quality, but in later work, these were collapsed into five factorsreliability, assurance, tangibles, empathy and responsiveness -that create the acronym RATER.
Businesses using SERVQUAL to measure and manage service quality deploy a questionnaire that measures both the customer expectations of service quality in terms of these five dimensions, and their perceptions of the service they receive. When customer expectations are greater than their perceptions of received delivery, service quality is deemed low.
In addition to being a measurement model, SERVQUAL is also a management model. The SERVQUAL authors identified five Gaps that may cause customers to experience poor service quality.

E-learning
It goes without saying that education is the best investment and a route to better life. New internet technologies made for the development of methods for delivery in education. E-learning was successfully implemented into the curriculum of many schools and colleges and as the result demonstrated how effective ICT use can be in supporting learning and teaching across a wide range of subject areas. If we look through the term "elearning" in Wikipedia it turns out that it belongs to European programs in the field of education and promotes the penetration of ICT in all learning systems and environments. E-learning is becoming leading in all fields of education and learning policy. It can be freely said that it has a great potential to change teaching and learning drastically. Notably, by developing capital infrastructure and providing quality interactive content ICT can transform institutions" delivery services. It can also be used in improving supporting teacher teaching and assessment. E-learning includes the fields of online learning, web-based training and technologydelivered instruction as well. It is a virtual world that stimulates students to take part in the educational process as they are involved in the activity of exploring and playing with the lessons material, communicating and cooperating with other students and teachers in performing several tasks such as description of electronic commerce issues that is the most attractive topic in the new information society. Usually traditional classes and seminars are focused on group learning whilst e-learning enables students self-paced and individual learning at home. These home based learning courses help students to arrange their time the way they want and take additional courses to learn or improve their skills if they find this necessary. E-learning differs from traditional courses as it provides wide range of exercises, animation, sound and testing that helps to keep student"s attention and interact in the teaching process effectively.
Benefits of e-learning to students, faculty and stuff cannot be overestimated. Access to learning materials at any time helps the student to refresh his memory and will never lose the course syllabuses. Elearning also enables trainee to fulfill requirements for a degree as it is an ideal tool for certification and his results and progress can be tracked. Lectures can use e-learning materials as lecture notes or presentations, syllabus, tutorial, assignments, quizzes, tests or exercises to support presentations with ancillary tools. E-learning increases education productivity and profitability, more over according to Charles Clarke"s paper "Foreword to Towards a Unified e-Learning Strategy" (July 2003) "E-learning has the potential to revolutionize the way we teach and how we learn. A great deal of progress has been made so far, but there is much more to do. E-learning can take us a further step forward. This is about embedding and exploiting technologies in everything we do, and getting ICT embedded across the curriculum for all subjects and in all pedagogues." What is e-learning? E-learning involves the use of a computer or electronic device (e.g. a mobile phone) in some way to provide learning, educational or learning material (Derek Stockley 2003). We can define e-learning as 'the use of technologies in learning opportunities'. This is a very broad definition but has been used in the context of the HEFCE (Higher Education Funding Council for England) e-Learning strategy:"The Government e-learning strategy defines e-learning as any learning that uses ICT. In embedding this strategy we want to ensure that there is confident use of the full range of pedagogic opportunities provided by ICT. For HE this will encompass flexible learning as well as distance learning, and the use of ICT as a communications and delivery tool between individuals and groups, to support students and improve the management of learning". (HEFCE elearning Strategy March 2005 p.5.).
Although electronic learning or shortly elearning is the term used to indicate any electronically assisted instructions it is mostly associated with instruction offered via computer or internet. But in many ways it is associated with ALT (advanced learning technology) that deals with both methodologies and technologies in learning by using networked and multimedia technologies.

E-learning vs. traditional education
"Once we free ourselves from the mental limits of viewing this technology as a weak sister to face-to-face synchronous education, the potentials to revolutionize education and learning become readily apparent" (Turrof, 1995). Although there is no finding to support an opinion that the best learning is traditional and the other models are inferior or less efficient such argument exists, but research shows that e-learning is at least as good as traditional education. E-learning doesn"t mean replacement of lectures or tutors it just enhances the learning process. To suit differing educational needs and aspirations of students universities must provide quality and flexibility. But it is clear that implication of increased workload requires proactive and effective management. Alongside this, transition to e-learning will inevitably lead to fundamental changes in the structure of traditional learning. And the problems associated with the change must be fully understood and taken into account before the transition-taking place. It is found that e-learning has positive effects not only on the student"s commitment to the learning process but on the creations a greater commitment on the students" part to learning. According to David Rashty (2001) the following table summarizes several opinions regarding the comparison between traditional learning and eLearning: The teacher usually talks more than the student The student talks at least as much as or more than the teacher

Learning Process
The learning is conducted with the whole class participating; there is almost no group or individual study Most of the learning process takes place in groups or by the individual student.

Subject Matter
The teacher conducts the lesson according to the study program and the existing curriculum The student participates in determining the subject matter; the studying is based on various sources of information, including web data banks and net-experts located by the student.

Emphases in the Learning Process
The students learn "what" and not "how"; the students and the teachers are busy completing the required subject matter quota; the students are not involved in inquiry-based education and in solving problems, but rather in tasks set by the teacher.
The students learn "how" and less "what"; the learning includes research study which combines searching for and collecting information from web data banks and authorities on the communications network; the learning is better connected to the real world, the subject matter is richer and includes material in different formats.

Motivation
The students' motivation is low, and the subject matter is "distant" from them.
The students' motivation is high due to the involvement in matters that are closer to them and to the use of technology.

Teacher's Role
The teacher is the authority The teacher directs the student to the information.

Location of Learning
The learning takes place within the classroom and the school The learning takes place with no fixed location

Lesson Structure
The teacher dictates the structure of the lesson and the division of time

Benefits of e-learning
"Good teaching is good teaching, no matter how it's done." The old adage still rings true, and e-Learning brings with it new dimensions in education. E-learning believes to be highly beneficial as promotes new entrants into the higher education market. E-learning solves many problems of traditional approach. The benefits of e-learning are stated in several e-leaning web sites.

Benefits for staff
Benefits for students Benefits for organization More effectively and efficiently managed and organized course materials; Encourage anytime-anyplace access to course materials; E-learning can be "on demand". It overcomes timing, attendance and travel difficulties; Reduce the need for certain administrative tasks (for example, making paper copies, marking tests, giving out course reminders); Provide self-directed and self-paced learning, allowing students to keep track of their own progress; More effective training. Studies indicate that trainees' retention rates are as much as 75% higher when using e-learning programs vs. traditional training methods; Ability to monitor student participation and progress, possibility of directed support and quickly advices, and options for making more effective use of staffstudent contact time; Increase opportunities for student participation, encouraging less confident students to take part; Less expensive training. Costs go down as the number of trainees' increases. This enables an organization to cost-effectively increase the number of personnel trained, leading to higher levels of employee satisfaction and superior company performance; Widen communication opportunities with students; Support different learning styles (using flexible learning materials); By using e-learning the course catalogue can be expanded; Help to change teachers' role from "knowledge provider" to "learning facilitators", promoting self-directed learning; Promote student engagement (using interactive learning materials), improving learner motivation and satisfaction; Implemented correctly, it can reduce some of the cost associated with education; Reduce large-group teaching and increase time spend with small groups or individuals; Enhance opportunities for collaborative group work; Support the development with flexible learning materials; Improve communication with course tutor and teaching assistants;

RESEARCH METHODOLOGY
Research methodology is a scientific way to get the data with the purpose and usefulness. Type of the research methods used is quantitative research. This quantitative research method sees reality / phenomenon / phenomena that are causal. This method is used to examine the population or a particular sample, the sampling technique is generally done at random, data retrieval using research instruments, quantitative data analysis or statistic in order to test the hypothesis that has been established. Types of quantitative research methods used is descriptive method. The purpose of descriptive research is to describe systematically the facts and the properties of a given population in a factual and accurate.
Stages of the study consisted of five (5) steps, as follows:

Define Variables and Dimensions to be Measured
The variable is a concept that has a variation in value. The variables to be measured to determine the quality of the e-learning by using ServQual is:  Independent Variable (X) = website content (X1), reliability (X2), responsiveness (X3), empathy (X4), e-learning quality (Y);

Creating and Spreading Questionnaire
In quantitative research, there are three methods of data collection, interviews, questionnaires and observation. In this research, using a questionnaire. Questionnaire method is a technique of data collection conducted by providing the questions or written statement to the respondent. While the measurement technique used is the Likert Scale. This scale is used to measure

RESULTS PROCESSING DATA OF THE QUESTIONNAIRE ANALYZING THE RESULTS PROCESSING DATA OF QUESTIONNAIRES DRAW A CONCLUSION
attitudes, opinions, and perceptions of a person or a group of social phenomenon. The 5 point of Likert Scale is the most common scale. Making the questioner shall refer to the variables and dimensions have beendetermined. Furthermore, the questionnaires distributed directly to the respondents selected with due regard to the characteristics and methods of sampling in accordance with conditions on the ground.
For every choice answers of respondents were scored as shown in Table 3.2 below: Strongly agree 5

Results Processing Data of the Questionnaire
Data were analyzed direct result of spreading questioner, then do the analysis process by using software R Programming. Further processing results can be processed using statistical models with descriptive analysis.

Descriptive Data Analysis
Descriptive data analysis is used to measure the Mean average of respondents' answers. Description of data to be presented include the value of Mean (M), Median (Me), Modus (Mo) Standard Deviation, the ideal Mean value and the ideal Standard Deviation value. To calculate the ideal Mean value and the ideal Standard Deviation value use the following formula: Besides that, it also presented a frequency distribution table. To determine the tendency of respondents to the research variables grouped by three rankings (Suharsimi Arikunto, 2006), namely: 1. Grouped of High Level All respondents who had scores as much as the average score plus 1 standard deviation upward (> Mi + 1 SDi).

Group of Medium Level
All respondents who had scores between the average score minus 1 standard deviation and the average score plus 1 standard deviation (between Mi -1 SDi to Mi + 1 SDi).

Group of Low Level
All respondents who had lower scores than average score of minus 1 standard deviation (< Mi -1 SDi).

Classical Assumption Test
Classical assumption is test that conducted before multiple regression analysis test. 98 W= (∑ i=1 n α i χ ( i ) ) 2 ∑ i=1 n ( χ i -χ ‾ ) 2 where: χ i = are the ordered random sample values α i = are constants generated from the covariances, variances and means of the sample (size n) from a normally distributed sample.

Multicolinierity Test
Multicolinierity test used to test whether the regression model have a correlation between independent variables [Ghozali2011]. A good regression model should be free of multicolinierity. It performed by looking at the value of Variance Inflation Factor (VIF) from each independent variable. In regression is said there have a multicolinierity if value of VIF > 10.
To determine the value of VIF is used the following formula: VIF= 1 1-R k 2 where R k 2 is the multiple coefficient of correlation.

Autocorrelation Test
Autocorrelation test is used to test whether in the linear regression there is a correlation between the confounding error in t period with confounding error in t-1 period. If there is an correlation means that it have autocorrelation. One of the assumptions that must be met of equation regression models are free of autocorrelation. To determine whether there is a correlation in this research is used a Durbin-Watson test (dWTest) with following formula: dW = ∑ t=2 T ( e t -e t-1 ) 2 ∑ t=1 T e t 2 where: T = number of observations e t = residual for period t To decide whether there is autocorrelation or not, follow the provisions of the following: dW < dL= It has positive autocorrelation (+) dL < dW < dU= Inconclusive dU < dW < 4-dU= There is no autocorrelation 4-dU < dW < 4-dL= Inconclusive dW > 4-dL= It has negative autocorrelation (-)

Heteroskidastity Test
Heteroskidastity test used to test whether the regression model occurred inequality residual variance from one observation to another. The test is performed by using Breusch-Pagan test. It can be used to determine the existence of spatial heterogeneity. The test statistic for the Breusch-Pagan test, which has a chi-square distribution is calculated as: BP chi-square test = n x R resid 2 with k degrees of freedom where: n = the number of observations R resid 2 = R 2 from a second regression of the squared residuals from the first regression on the independent variables k = the number of independent variables The level of trust that taken is 95% which is understood as the level to which a 95% value of the sample will represent the value of a population where the sample came from. The significant value of 95% is 0.05. Criteria for the heteroscedasticity in a regression model is if pvalue < 0.05. If p-value > 0.05 then the research can be continued.

Multiple Regression Analysis
Regression analysis is one of statistical data analysis techniques are often used to examine the relationship between several variables and predict a variable [Kutner2004]. Regression menu on R programming is a tool used to measure the effect of independent variables on the dependent variables and predict the dependent variable using independent variables. If the dependent variable associated only with one independent variable, then the resulting regression equation is simple linear regression. If the dependent variable is associated with more than one independent variable, the regression equation is linear multiple linear regression.

Required Analysis
General

Correlation Coefficient (r/R)
Correlation coefficient is the coefficient used to determine the relationship between variables X and Y, the condition is: 1. If r = 0 or close to 0, then the relation is very weak or no relationship at all. 2. If r = +1 or close to +1, then strong and direct relationship. 3. If r = -1 or close to -1, then the relationship is strong and not unidirectional.

Coefficient of determination (r2/R2)
Coefficient of determination is a coefficient used to determine how much the independent variable (X) affects the dependent variable (Y). The coefficient of determination range is from 0 to 1.

Standard Error of Estimate
Used to determine the accuracy of estimation equations. It can be used to measure the size of the standard error of estimate (the smaller value of his guilt then the higher the accuracy)

Hypotheses Test
Hypotheses used in this research is associative hypotheses. Associative hypotheses are allegations of whether there is a significant relationship between two or more variables. Hypotheses testing is used to determine whether there is an influence between independent variables with the dependent variable. It begins with simultaneous hypothesis testing (F), partial hypotheses test (T) and the coefficient of determination.

Coefficient of Determination Test
Coefficient of determination test is used to determine how much the independent variables have an influence on the dependent variable. To determine the coefficient of determination value is used the following formula: kd= r 2 x100% where: kd = Coefficient of determination r = Coefficient of correlation

F Test
Simultaneous test (F test) was conducted to see the effect of the independent variable on the dependent variables simultaneously.
To determine the value of F is used the following formula: F= R 2 /k ( 1-R 2 ) /( n-k ) where: R 2 = Coeficient of determination n = Number of samples k = Number of independent variables 3. T Test T test (partial) was conducted to see the effect of the independent variables to the dependent variable partially. To determine the value of T is used the following formula: T= r n-2 1-r 2 where: r = Coefficient of correlation n = Number of samples

Analyzing the Results Processing Data of Questionnaires
Analytical results from the processing of questionnaires is a target that would be the purpose of achieving the level of quality of existing information systems. The end result can be expressed in a numerical value that reflects the interests of the variables and dimensions in user satisfaction performance. Determination of the value of these results are based on the gap between expectations and satisfaction received today. Value negative gap means a lower than expected.

Variable and Variable Operational Research
In the research, should have a good measuring tool. This measure is usually referred to as the research instrument. Research instrument is a tool used to measure the natural and social phenomena being observed. Specifically, it is named as a research variable.
There is one variable used in this research, the independent variable. The independent variable is the variable that affects or is the cause of the change or the emergence of the dependent variable.
The independent variable is the data obtained from the factors contained in the End User Computing Satisfaction method to determine user satisfaction of the students in Uzbekistan.
Operational variables used in this research are presented below in Table3.4:

Empathy
The instructor is genuinely concerned about the students(EMP1) 1-5 The instructor understands the individual needs of students(EMP2) 1-5 The instructor has the student's best long-term interests in mind(EMP3) 1-5 The instructor encourages and motivates students to do their best(EMP4) 1-5

Responsiveness
The instructor quickly and efficiently responds to student needs(RES1) 1-5 The instructor is willing to go out of his or her way to help students(RES2) 1-5 The instructor always welcomes student questions and comments(RES3) 1-5

E-learning quality
Responsiven ess

Reliability
Web site content The web site uses audio elements properly(WSC1) 1-5 The web site uses video elements properly(WSC2) 1-5 The web site uses animations/graphics properly(WSC3) 1-5 The web site uses multimedia features properly(WSC4) 1-5 The web site provides useful information(WSC5) 1-5 The web site provides accurate information(WSC6) 1-5 The website provides high quality information(WSC7) 1-5 The information on the web site is relevant to me(WSC8) 1-5

E-learning quality
Your perception of the overall quality of the instruction you get from online learning is (poor-excellent) (eLQ1) 1-5 The instructional web site seems to be up to date(eLQ2) 1-5 The instructional web site works well(eLQ3) 1-5 The instructional web site has clear instruction(eLQ4) 1-5

Variable, Definition and Attribute
In this section will explain the variables that are used together with their explanations and the attributes.

Reliability
Refers to the ability to provide the promised service accurately and reliably.
Realizes non-functional requirements used to evaluate the performance of a system Responsiveness The willingness to help users and provide proper attention.
Has a positive association with students' perceptions of elearning quality. Empathy Includes the care and individual attention to the users.
Has a positive association with students' perceptions of elearning quality.

User Satisfaction
The attitude of a user to the computer system (s)he employs in the context of his/her work environments Has a positive association with students' perceptions of elearning quality.
Web Site Content Can be defined as the presentation and layout of information and functions that capture the overall firm presence and its public image, and is assumed to affect how a customer perceives web service quality.
Has a positive association with students' perceptions of elearning quality.
E-learning quality The student needs to make decisions and learn from the consequences Has a positive association with students' perceptions of elearning quality.