The Newborn

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
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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.