THE ROBUSTNESS OF INFANTS DETECTION OF VISUAL-MOTION

Fourteen-week-olds were tested for detection of the movement of a smal l vertical bar with varying levels of visual complexity using a speede d version of the forced-choice preferential looking (FPL) paradigm. Th e target bar horizontally oscillating at temporal frequencies of 0.6, 1.2 or 2.4 Hz could appear amidst 1, 5, or 13 other static bars. Detec tion accuracy was (a) generally unaffected by the complexity of the vi sual field, (b) affected by the distance of the moving bar from the ce nter of the screen, and (c) affected directly by temporal frequency. R esponse times depended inversely on temporal frequency. When the simil arity of the static elements was decreased by making them chromaticall y heterogeneous, the FPL observer's average response time increased, a lthough detection accuracy remained the same. The FPL observer's respo nse times actually decreased slightly as more heterogeneous distracter s were added. Adults tested using an FPL observer also showed this sam e effect. Both infants and adults showed disproportionately long respo nse times on incorrect trials when only 1 other distracter was present in the visual field. The number of static elements in the visual fiel d and their similarity affected primarily the speed with which infants at this age responded to movement.