Function of attention in infants is explored. Assuming (1) that infants respond differently to novel situations than to familiar ones; (2) that the infant's pattern of response is a partial reflection of the process of acquiring a perceptual memory of the stimulus, and (3) that sex differences may occur in the rate of habituation, 120 infants either 12 or 18 weeks old received five presentations of a standard stimulus. After this, when the infant displayed a fixation of less than 3 seconds, the number of additional trials needed established their habituation criteria. Discrepancies of 0,1,2, or 3 arbitrary units were introduced on the next trial. Results indicate that while young infants took longer to habituate than older ones, they showed no differences in response to discrepancies. If a new stimulus is presented before habituation is complete, infants respond differently than they would otherwise do. Conclusions are (1) Sex differences may reflect differences in maturation rates, (2) Developmental processes during the first few months of life may influence memorizing more than using what is learned and (3) Infants may moderate discrepancies by ignoring those he is not ready to assimilate. (DJ)