The role of variation as a determinant of infant categorical responding was investigated in three studies of infants 7 to 7 1/2 months of age. Sixty-three infants, divided into groups of 21 each, were habituated to color slide poses of either one, two, or six different adult female faces. Their responses to a novel pose of a familiar face and a novel pose of a novel face were observed. In every condition, infants generalized habituation to the familiar face, but only infants shown six different faces during habituation responded categorically (that is, generalized habituation to the novel face). Infants shown poses of one, two, and even three different faces during habituation dishabituated to the novel face. They did so even when offered only as many presentations of each particular face during familiarization as were the infants shown poses of six different faces. Thus, infants exposed to limited variation seemed to respond on the basis of memories for the specific few exemplars they had seen, rather than on the basis of an abstracted representation of their shared attributes. It was suggested that infant categorical responding may betoken not an active search for invariants but a passive failure of memory for details, which occurs only when the details are too numerous to keep track of individually. (Author/RH)