Concept Acquisition in the Human Infant.

This experiment examined developmental changes in the ability of infants to learn conceptual categories regarding the human face. A total of 108 infants, aged 18, 24, and 30 weeks, were habituated to (1) the same face in the same orientation, (2) the same face in differing orientations, or (3) different faces in different orientations. All subjects were then tested for generalization of habituation with a familiar face in a novel orientation and a novel face in a novel orientation. Results for both fixation times during post-habituation trials and dishabituation to the test stimuli indicated little conceptual categorization at 18 weeks, possibly the beginnings of such categorization at 24 weeks, and evidence for responding at two different categorical levels (both that of a"specific face regardless of orientation" and "faces in general") at 30 weeks of age. These results suggest that concept acquisition ability may be present at a much younger age than had previously been believed. (Author/MS)