The Developmental Study of Apparent Movement

Abstract

Differences in thresholds of apparent simultaneity and apparent movement were observed with normal and brain-damaged children of different ages. In an attempt to explore this relationship more fully, III subjects between 2 ½ years and 19 years were tested on a modified Withers tachistoscope. It was found that changes in thresholds of apparent simultaneity and apparent movement were clearly a function of age. Both illusions were seen under objectively more difficult conditions—slower flash frequencies—by younger children. The decrease of the illusions with age continued until about 14 years, and then levelled off. No sex differences were observed. A second investigation of closure ability indicated that an explanation of the apparent movement changes in terms of greater closure ability in younger children was not tenable, since ability to form a gestalt under difficult conditions increased as a function of age. In the light of other investigations on age and illusions it is possible that the change in apparent movement is due to an increase of discrimination with age. On the other hand, the similarity between the frequency of apparent-movement thresholds and dominant brain rhythms, as well as their parallel changes with age, may point to some more basic neurophysiological growth change.