Visuo-motor development which causes detection of visual depth from motionand density cues

This study examines the effectiveness of cues of visual depth and distance in the course of development and how this process depends on visuo-motor de velopment. In the visual pitfall situation, i.e. a modification of Gibson's visual cliff; eight Japanese monkeys (macaca fuscata) were observed with r espect to their depth avoidance and visuo-motor activity. The tests were ru n once a week from the first until the sixteenth week after bit th. Binocul ar parallax, motion parallax and texture density rates were manipulated to examine their effectiveness as cues. It was shown that for the first two mo nths depth perception depended exclusively on motion parallax, whereas in t he third month cues of motion and texture were added. Binocular cues did no t have ally effect in this age range. Three items of behaviour, i.e. visual regard of depth. head movement, and body movement, were checked and measur ed to obtain information which could explain the process of development of the cue function. The three items showed different developmental curves. Du ring the first month, visual regard closely concurred with head and body mo vements, then visual activity suppressed motor behaviour and, after the end of the second month, the two became almost independent of each other. These analyses demonstrated that at a later stage pictorial cues produced a n effect additional to the primary motion cues and that the effective cue f unction was based on the development of visuo-motor activity.