Touch latency has been shown to reduce users' performances but most studies focus on one-handed elementary tasks such as pointing or tracking a single object. The everyday use of touch devices is made, however, of more complex "composite" tasks combining several objects with potential bimanual interaction. Such a composite task may increase users' cognitive load which makes latency less perceivable. We thus expected that the impact of latency on users' performances should be smaller in composite tasks than in elementary tasks. We tested this hypothesis by comparing the degradation effect of latency on users' performances in an elementary vs. a composite task. The elementary task consisted in positioning a single object. The composite task involved sorting and positioning objects with a two-handed interaction, inducing more complex planning and motor strategies that could be seen as an additional cognitive load. Contrary to expectations, the degradation effect was comparable in the two tasks. This study indicates that the substantial hindrance of latency, demonstrated on elementary tasks, also exists in more complex tasks that better represent the every day use of touch devices. This strengthens the motivation to question the interaction between the task properties and latency effect and to adapt commercial devices and applications accordingly.
['Elie Cattan', 'Amélie Rochet-Capellan', 'François Bérard']
Effect of Touch Latency on Elementary vs. Bimanual Composite Tasks