| Abstract: | The development of the visual placing response was studied in the human infant using an apparatus that controlled the visual stimulus (texture density of patterns) and the depth at which stimuli were presented. The visual placing response was found to be nearly an all-or-none response having an acute onset at between 170 and 190 days of age. The response is identified in the human infant by rigid extension of the hands and arms, characteristically with the fingers fanned. Shortly after it develops, the response appears to be visually mediated and is well differentiated with respect to increasing depth. In contrast, the older infants showed less well differentiated visual placing, tending to respond to all depths equally. The results suggest that there are two phases in the development of the response. The first phase is the initial acquisition of the response and is determined largely by visual depth. The second phase occurs later in development, near the time of walking, and seems to be determined by several factors, including both texture density and depth. |
