An investigation of object permanence and its relationship to smooth pursuit eye movement

The aim of the present thesis was to investigate the role of 'object permanence' in smooth pursuit eye movement in humans. Churchland, Chou, and Lisberger (2003) found that smooth pursuit eye velocity was maintained in monkeys when target motion was occluded by an object in comparison to a condition where target motion was briefly removed, suggesting that object permanence may facilitate the maintenance of smooth pursuit velocity. In the present thesis, two smooth pursuit eye velocity intervals were measured in nine conditions. In each condition the motion of a target was interrupted for 200ms, either by removal in a series of gap-like conditions, or occlusion by a real object, a computer-generated object, or an illusory object stimulus. Baseline smooth pursuit eye velocity was also recorded without target interruption. Eye velocity was measured at two intervals: 100ms pre-interruption and 120ms post-interruption, and the difference between these intervals yielded a Mean Change in Eye Velocity value. Analyses partially supported the findings of Churchland et al., with Mean Change in Eye Velocity in the Gap condition significantly greater than Baseline smooth pursuit eye movement. However, no such difference was found between Baseline and the computer generated Object, Real Object, or Illusory Object conditions. Overall, there was a clear, though non-statistically significant, pattern in the raw data indicating that object permanence may play a role in allowing smooth pursuit eye velocity maintenance as suggested by Churchland et al., and it is proposed that the eye velocity memory component of their model may function on a continuum of engagement. It was concluded that the findings provide some evidence for object permanence promoting the maintenance of human smooth pursuit eye velocity when an object blocks the perception of target motion