THE NEWBORN Babies can see, hear, and respond to interesting sights, sounds, and other sensory stimuli at a much earlier age than was originally believed.A New Baby's Reflexes The newborn, or neonate, has a repertoire of reflexes, or involuntary responses to external stimuli. Many of these reflexes, some of which have obvious value in helping the newborn survive, disappear during the first year of life.Infant States Babies experience predictable changes in state, or recurring patterns of alertness and activity level, ranging from vigorous, wakeful activity to quiet, regular sleep. Two significant infant states are sleeping and crying. The amount of sleep in which children engage and the nature of their sleep both change gradually until about adolescence, when both parameters conform to a more adult pattern. Between the ages of 2 and 4 months babies may fall prey to sudden infant death syndrome (SIDS). Although the causes of SIDS are as yet unexplained, this fatal disorder usually occurs in winter and after a cold. Preventive measures include the cessation of parental smoking, preventing infants from sleeping on their stomachs, and parent and infant cosleeping. The autostimulation theory proposes that infants spend more than twice as much time as adults in REM sleep because such sleep stimulates higher brain centers that in turn promote development of the central nervous system. As babies become more able to process external stimulation, they spend more and more time in non-REM sleep, approaching the adult level at about the age of 3. Crying, which is an effective means of early communication, follows distinct patterns that also change with development.How to Soothe an Infant Although there are wide differences among individuals, sexes, and races in soothability, certain caregiver techniques, such as holding the baby on the shoulder or swaddling it, are widely successful in helping to calm a distressed baby. Infants can also help to soothe themselves, as when they quiet after starting to suck on a thumb or pacifier.Evaluating the Newborn's Health and Capabilities Tests of reflexes may be combined with other assessments to gauge the health, maturity, and capacities of a newborn. The Brazelton Neonatal Assessment Scale is one widely used assessment tool. THE INFANT'S SENSORY AND PERCEPTUAL CAPACITIESUnlocking the Secrets of Babies' Sensory Capabilities Infants' sensations and perceptions are no longer completely obscure to researchers, who have learned how to measure infants' sensory and perceptual capacities. In their efforts to understand whether babies can distinguish between one stimulus and another investigators often make use of the infant's tendency to habituate, or become used to, a given stimulus. Another technique is to use the visual preference method, in which researchers pinpoint a baby's preference for one of two alternative stimuli.Hearing: Babies are Good Listeners At birth, babies are more sensitive to high-pitched sounds than low-pitched ones, and a sound must be slightly louder for them to detect it. Overall, however, a newborn's hearing is very well developed. Newborns can distinguish among different kinds of sounds and tell what direction a sound comes from. They are also predisposed to respond to human voices, which may be significant for later social and language development.Vision: How Babies See Their Worlds Although visual capacities continue to develop throughout the first year of life, newborns are sensitive to brightness and movement, can distinguish colors, and can track moving objects. Because they cannot focus their eyes very well, newborns do not have good visual acuity at distances beyond close range, but their acuity improves in the first 3 months of life. During the same period they become better able to perceive patterns, including the patterning of human faces. The accurate perception of distance improves with age as well, as babies begin to coordinate their two eyes and use stereoscopic vision. Experiments with the visual cliff demonstrate that by the time babies are between 6 and 14 months old they are capable of depth perception. Shape constancy is something that even newborns seem to possess. Size constancy, however, appears to be a skill that develops partly through experience.Smell, Taste, and Touch Newborns can discriminate among a variety of odors, and by 1 week of age they have learned to distinguish their mother's smell from those of other people. Newborns are also able to discriminate different tastes, and they display a preference for sweet over sour or bitter. The sense of touch is activated long before birth, and newborns are clearly responsive to both positive and negative types of touch; contrary to past beliefs, they are highly sensitive to pain. Infants also quickly learn to discriminate among objects based only on their sense of touch.Intermodal Perception: How Infants Transfer Learning From One Sense to Another From a very early age, using their capacity for intermodal perception, babies can integrate information from two different senses, such as the sounds that go with a certain sight. This finding challenges the commonly held view that infants begin life experiencing totally unrelated sensations in each sensory system. EARLY LEARNING AND MEMORYClassical Conditioning Even newborns can be classically conditioned when a previously neutral stimulus is repeatedly paired with a pleasant stimulus that naturally elicits some involuntary response. Eventually, the previously neutral stimulus alone comes to elicit the same reaction. Classical conditioning is more difficult in newborns when an aversive stimulus is involved. Young babies don't seem to be biologically prepared to learn such associations easily.Operant Conditioning Newborns can also learn to emit a certain behavior when that behavior is repeatedly rewarded. Successful operant conditioning in newborns typically involves a behavior like sucking, which is a component of feeding and of considerable importance to the baby's survival. This suggests that young babies are best organized to learn conditioned responses that are functionally adaptive.Learning Through Imitation Although newborns may be capable of some imitation, the basis of the ability to imitate others and the amount of such behavior the child displays change significantly with age. By the early toddler period, at the age of about 1½ children cannot only readily imitate others, but also can defer imitation and generalize imitated behavior to new settings.Memory in Babies When given adequate retrieval cues for something they have learned, babies can remember information over a substantial period of time. Thus, rather than having poor memories, as many people assume, it appears that infants just need the right reminders to help them access the information they have stored.