Abstract

After prolonged inspection of motion in a particular direction, subsequent viewing of a stationary stimulus induces the perception of motion opposite to adaptation. This is the historical waterfall illusion, today referred to as the motion aftereffect (MAE). The purpose of this dissertation was to posit a functional theory which better explains the underlying neuropsychological mechanism responsible for the production of the motion aftereffect. A psychophysical approach was employed to test the predictions which stem from the traditional fatigue and the recalibration models. To investigate this question, this series of experiments examined the most difficult challenge to the conventional fatigue interpretation, that is, the storage of the motion aftereffect. In Experiment 1, MAE duration was recorded for variable adaptation durations and the decay of the MAE was tracked. In Experiment 2, MAE duration was measured following uninterrupted- versus interrupted-adaptation to test for storage via summation across adaptation episodes. Experiment 3 examined the effect of the intervening visual environment on the long-term storage of the MAE. Finally, Experiments 4a and 4b investigated the time course of immediate and long-term MAEs which were induced in opposite directions to each other. All experiments yielded evidence of MAE storage. The time course for recovery from adaptation illustrated a fast component, independent of the visual environment, like that postulated by traditional fatigue models. As well, a slower mechanism was evident from the data, which did depend on one's visual experience, and hence is consistent with the notion of visual recalibration.