The COG bias is evolutionarily adaptive: eye movements will bring both the saccade target as well as nearby objects into high acuity vision, thereby maximizing the amount of information obtained with each saccade. Motor preparation or “efferent readiness” to execute an undershooting or overshooting saccade, Coren found, however, can also give rise to a corresponding illusion of extent (1986: 404–406). Observers, e.g., will perceptually underestimate the length of the distance between the point of fixation and the saccade target when there is an extraneous stimulus on the near side of the target (as in the second row of Figure 3) and will perceptually overestimate the length of the distance when there is an extraneous stimulus on the far side of the target (as in the third row of Figure 3).