[Apparent motion effect under undetermined trajectory of presentation of test dot stimuli]

The influence of such factor as determinacy of trajectory of stroboscopically presented test spot on apparent movement illusion appearance, was studied. Six subjects took part in psycho-physiological experiments during which a test spot was presented successively along the straight line to observer on a display, randomly deviating from this line up or down by 0.39, 0.78, 1.17 or 1.56 angular minutes. It was computed that with the test spot deviating by 0.92 angular minutes from the straight trajectory prognosticated by the observer, the probability of disappearance of apparent straight uniform motion of the spot was equal to 0.75. The findings suggest than one of the conditions under which apparent movement illusion appears involves an agreement between the shape of trajectory of test object presentation as expected by the observer, and its real shape in the experiment.