347 Beginnings chance of being blind, deaf, or mentally retarded or of having a malformed heart. If the mother has rubella later in the pregnancy, after the infant’s eyes, ears, brain, and heart have formed, the likelihood that the baby will have one of these defects is much lower. Later, during the fetal stage, teratogens affect the baby’s size, behavior, intelligence, and health, rather than the formation of organs and limbs. Of special concern today are the effects of drugs on infants’ development (e.g., Gendle et al., 2004; Jones, 2006). Pregnant women who use substances such as cocaine create a substantial risk for their fetuses, which do not yet have the enzymes necessary to break down the drugs. “Cocaine babies” or “crack babies” may be born premature, underweight, tense, and fussy (Inciardi, Surratt, & Saum, 1997). They may also suffer delayed physical growth and motor development (Tarr & Pyfer, 1996). Current research suggests, however, that although cocaine babies are more likely to have behavioral and learning problems (Singer et al., 2001; Singer et al., 2002; Tan-Laxa et al., 2004), their mental abilities are not necessarily different from those of any baby born into an impoverished environment (Frank et al., 2001; Jones, 2006). How well these children ultimately do in school depends on how supportive that environment turns out to be (Begley, 1997; Messinger et al., 2004; Singer et al., 2004). Alcohol is another dangerous teratogen, because it interferes with infants’ brain development (Avaria et al., 2004). Almost half the children born to expectant mothers who abuse alcohol will develop fetal alcohol syndrome, a pattern of defects that includes mental retardation and malformations of the face (Jenkins & Culbertson, 1996). Pregnant women who drink as little as a glass or two of wine a day can harm their infants’ intellectual functioning (Streissguth et al., 1999). Those who engage in bouts of heavy drinking triple the odds that their child will develop alcohol-related problems by the age of twenty-one (Baer et al., 2003). Smoking, too, can affect the developing fetus. Smokers’ babies often suffer from respiratory problems, irritability, and attention problems, and they are at greater risk for nicotine addiction in adolescence and adulthood (Buka, Shenassa, & Niaura, 2003; Gilliland, Li, & Peters, 2001; Law et al., 2003; Linnet et al., 2005; Niaura et al., 2001). Worse, they may be born prematurely, and they are usually underweight. Babies who are premature and/or underweight—for whatever reason—are likely to have cognitive and behavioral problems that continue throughout their lives (Bhutta et al., 2002; Jefferis, Power, & Hertzman, 2002). Defects due to teratogens are most likely to appear when the negative effects of nature and nurture combine. The worst-case scenario is one in which a genetically vulnerable infant receives a strong dose of a damaging substance during a critical period of prenatal development. The risk of behavioral and psychological difﬁculties in later life is also increased for children whose mothers were under signiﬁcant stress during the ﬁrst six months of pregnancy (Huizink, Mulder, & Buitelaar, 2004; Van den Bergh & Marcoen, 2004) or who got the ﬂu during that period (Brown et al., 2005). Fortunately, mental or physical problems resulting from all harmful prenatal factors affect fewer than 10 percent of the babies born in Western nations. The vast majority of fetuses arrive at the end of their nine-month gestation averaging a healthy seven pounds and ready to continue a normal course of development in the world. The Newborn fetal alcohol syndrome A pattern of defects found in babies born to women who drink heavily during pregnancy. Determining what newborns can see, hear, or do is one of the most fascinating and frustrating challenges for researchers in developmental psychology. Babies are extremely difﬁcult to study because they sleep about 70 percent of the time. When they are not sleeping, they are drowsy, crying, awake and active, or awake and inactive. It is only when they are in this latter state, which is infrequent and lasts only a few minutes, that researchers can assess the infants’ abilities. To do so, psychologists show infants objects or pictures and record where they look and for how long. They ﬁlm the infants’ eye movements and note changes in heart rates, sucking rates, brain waves, bodily movements, and skin conductance (a measure of perspiration that accompanies emotion) when objects are shown or sounds are 348 Chapter 9 Human Development made. From studies using these techniques, researchers have pieced together a fair picture of what infants can see and hear (Kellman & Arterberry, 2006). Infants can see at birth, but their vision is blurry. Researchers estimate that newborns have 20/300 eyesight. In other words, an object 20 feet away looks as clear as it would if viewed from 300 feet by an adult with normal vision. The reason infants’ vision is so limited is that their eyes and brains still need time to grow and develop. Newborns’ eyes are smaller than those of adults, and the cells in their foveas—the area in each eye on which images are focused—are fewer and far less sensitive. Their eye movements are slow and jerky. And pathways connecting the eyes to the brain are still inefﬁcient, as is the processing of visual information within the brain. Although infants cannot see small objects across the room, they can see large objects up close—the distance at which most interactions with caregivers take place. Infants look longest at objects that have large elements, movement, clear contours, and a lot of contrast—all of which can be found in the human face (Farroni et al., 2005; Turati, 2004). Newborns actively use their senses to explore the world around them. At ﬁrst they attend to sights and sounds for only short periods, but gradually their attention span lengthens, and their exploration becomes more systematic. In the ﬁrst two months, they focus only on the edges of objects, but after two months of age, they scan whole objects (Banks & Salapatek, 1983). Then, when they see an object, they get all the information they can from it before going on to something new (Hunter & Ames, 1988). Newborns stare at human faces longer than at other ﬁgures (Valenza et al., 1996). They are particularly interested in eyes, as shown in their preference for faces that are looking directly at them (Farroni et al., 2002). At two or three days of age, newborns can hear soft voices and notice differences between tones about one note apart on the musical scale (Aslin, Jusczyk, & Pisoni, 1998). In addition, they turn their heads toward sounds (Clifton, 1992). But their hearing is not as sharp as that of adults’ until well into childhood. This condition is not merely a hearing problem; it also reﬂects an inability to listen selectively to some sounds over others (Bargones & Werner, 1994). As infants grow, they develop sensory capacities and the skill to use them. Infants pay special attention to speech. When they hear someone talking, they open their eyes wider and search for the speaker. Infants also prefer certain kinds of speech. They like rising tones spoken by women or children (Sullivan & Horowitz, 1983). They also like high-pitched, exaggerated, and expressive speech. In other words, they like to hear the “baby talk” used by most adults in all cultures when talking to babies (Fernald, 1990). They even seem to learn language faster when they hear baby talk (Thiessen, Hill, & Saffran, 2005). Newborns also like certain smells and tastes better than others. When given something sweet to drink, they suck longer and slower, pause for shorter periods, and smile and lick their lips (Ganchrow, Steiner, & Daher, 1983). Within a few days after birth, breastfed babies prefer the odor of their own mother to that of another mother (Porter et al, 1992). Vision and Other Senses A BABY’S-EYE VIEW OF THE WORLD The top photograph simulates what a mother looks like to her infant at three months of age. Although their vision is blurry, infants particularly seem to enjoy looking at faces. reﬂexes Simple, involuntary, unlearned behaviors directed by the spinal cord without instructions from the brain. Reﬂexes and Motor Skills In the ﬁrst weeks and months after birth, babies show involuntary, unlearned reactions called reﬂexes. These swift, automatic movements occur in response to external stimuli. Figure 9.2 illustrates the grasping reﬂex, one of more than twenty reﬂexes that have been observed in newborn infants. Another is the rooting reﬂex, whereby the infant turns its mouth toward a ﬁnger or nipple that touches its cheek. And the newborn exhibits the sucking reﬂex in response to anything that touches its lips. Many of these reﬂexive behaviors evolved because they help infants to survive. The absence of reﬂexes in a newborn signals problems in brain development. So does a failure of reﬂexes to disappear as brain development during the ﬁrst three or four months allows the infant to control muscles voluntarily.