Haptic perception of material properties by 3-month-old infants

Three studies were conducted using a multiple trials procedure to investigate 3-month-old infants' ability to perceive material properties with their hands. In Study 1, infants discriminated stimuli which differed from one another in texture, temperature, compliance, and weight. In Study 2, infants discriminated stimuli which differed from one another only in weight. Infants evidenced discrimination by holding one stimulus longer than the other over trials, by involving both hands, and by increasing their general level of activity. A critical feature of both Studies 1 and 2 was that the stimuli were presented to infants in the pitch dark. In Study 3, infants were given the same stimuli as in Study 2, but under normal lighting conditions; they provided no robust evidence for discriminating the stimuli. We conclude that 3-month-old infants are able to perceive material properties, including weight differences, with their hands. However, they do so only under conditions which confine their attention, and they do not explore these properties with the specialized hand movements used by older infants and adults.