visual cliff

n. An experimental apparatus used to investigate depth perception in infants and small animals in which a clear surface covers a checkerboard pattern which goes to an edge and extends down a side to a lower level, as does a tablecloth draped over the edge of a table and onto the floor. Infants and young animals are placed near the edge, and their willingness to move over the edge is used to infer whether or not they are capable of perceiving depth.