Synchronous change and perception of object unity: evidence from adults and infants

Adults and infants display a robust ability to perceive the unity of a cent er-occluded object when the visible ends of the object undergo common motio n (e.g. Kellman, P.J., Spelke, E.S., 1983. Perception of partly occluded ob jects in infancy. Cognitive Psychology 15, 483-524). Ecologically oriented accounts of this ability focus oil the primacy of motion in the perception of segregated objects, but Gestalt theory suggests a broader possibility: o bservers may perceive object unity by detecting patterns of synchronous cha nge, of which common motion is a special case. We investigated this possibi lity with observations of adults and 4-month-old infants. Participants view ed a center-occluded object whose visible surfaces were either misaligned o r aligned, stationary or moving, and unchanging or synchronously changing i n color or brightness in various temporal patterns (e.g. flashing). Both al ignment and common motion contributed to adults' perception of object unity , but synchronous color changes did not. For infants, motion was an importa nt determinant of object unity, but other synchronous changes and edge alig nment were not. When a stationary object with aligned edges underwent synch ronous changes in color or brightness, infants showed high levels of attent ion to the object, but their perception of its unity appeared to be indeter minate. An inherent preference for fast over slow flash rates, and a novelt y preference elicited by a change in rate, both indicated that infants dete cted the synchronous changes, although they failed to use them as informati on for object unity. These findings favor ecologically oriented accounts of object perception in which surface motion plays a privileged role. (C) 199 9 Elsevier Science B.V. All rights reserved.