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Conditions for Young Infants' Perception of Object Trajectories


  • This research was supported by ESRC Grant R000238340, NIH Grant R01-HD40432, and NSF Grant BCS-0418103. We gratefully acknowledge the efforts of the infants and parents who participated in the studies, and extend our appreciation to Les Cohen for Habit computer software.

concerning this article should be addressed to J. Gavin Bremner, Psychology Department, Lancaster University, Lancaster LA1 4YF, UK. Electronic mail may be sent to


When an object moves behind an occluder and re-emerges, 4-month-old infants perceive trajectory continuity only when the occluder is narrow, raising the question of whether time or distance out of sight is the important constraining variable. One hundred and forty 4-month-olds were tested in five experiments aimed to disambiguate time and distance out of sight. Manipulating the object's visible speed had no effect on infants' responses, but reducing occlusion time by increasing object speed while occluded induced perception of trajectory continuity. In contrast, slowing the ball while it was behind a narrow or intermediate screen did not modify performance. It is concluded that 4-month-olds perceive trajectory continuity when time or distance out of sight is short.