Effects of luminance and texture motion on infant defensive reactions to optical collision

Infants saw a textured light area expand and contract on a dark rear-projection screen. The texture elements (15 black dots) expanded and contracted radially from the center of the screen as though they were on a single surface (single-depth display) or independent (multiple-depth display). None of the texture elements was on a "collision" trajectory with the infant's face. The single-depth display elicited greater defensive reactions (blinking and backward head movement) on expansion than contraction trials in both 4- to 8-week-olds and 10- to 14-week-olds. A different group of 4- to 8-week-olds did not exhibit greater overall blinking or backward head movement to expansion versus contraction of the multiple-depth display. The findings suggest that young infants utilize flow field information to distinguish between approaching subjective surfaces and voids in the regions between sparse texture.