Sensitivities of the Infant
The best criterion that can be used to determine the presence or absence of sensory capacity is the motor response to sensory stimuli that would normally arise when these sense organs are stimulated However, it is often difficult to tell whether a motor response is made to a stimulus or whether the reaction is a part of general mass activity. Nor does absence of response necessarily mean absence of sensitivity. It may mean only that the stimulus used was too weak to elicit a response.
An even more serious problem in studying the sensitivities of the infant is finding a suitable method of doing so. To date, for example, no reliable test for color vision in infants has been devised. Consequently, the knowledge of whether infants can see color or whether they are capable of only black-white vision has been determined indirectly from the study of the development of the cones in the eyes of infants who die at birth or shortly afterward. Because the cones are very undeveloped, it is assumed that new born infants are color blind.
There is ample evidence that the state of the infant influences reactivity. When infants are dazed by the birth experience, when they are drowsy or asleep. or when they are preoccupied with feeding, they will react differently to sensory stimuli than when their physical condition is better. The intensity of the stim ulus likewise has a profound influence on infant's re activity to different sensory stimuli. This explains, in part at least, the variations in the sensory abilities of different infants, just as it explains the variations in the sensory abilities of the same infant from time to time during the infancy period.
While present knowledge of sensory reactions of infants is somewhat limited, it is now believed that infants have a greater capacity for sensory discrimination than formerly was thought.
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