Setting the Context: Brain Blossoming and Sculpting

Because our large cerebral cortex develops mainly after birth, during the first two years of life, the brain mushrooms. Axons elongate and develop a fatty cover called myelin. Dendrites sprout branches and at synapses link up with other cells. Synaptogenesis and myelination program every ability and human skill. Although the brain matures for decades, we do not simply “develop more synapses.” Each region undergoes rapid synaptogenesis, followed by pruning (or cutting back). Before pruning, the brain is particularly plastic, allowing us to compensate for early brain insults—but synaptogenesis and learning occur throughout life.

Eating undergoes dramatic changes during infancy. We emerge from the womb with sucking and rooting reflexes, which jumpstart eating, as well as other reflexes, which disappear after the early months of life. Although the “everything into the mouth” phase of infancy can make life scary for caregivers, a 2-year-old’s food caution can protect toddlers from poisoning themselves.

Even though its specific health benefits are not always clear-cut, every public health organization advocates exclusive breast-feeding for the first 6 months of life. However, only a minority of women follows this recommendation. Mothers may find breast- feeding difficult and rebel against the social pressure to nurse for 6 months. We need to realize that breast-feeding is not for everyone and avoid equating nursing with being a good mom.

Undernutrition, both stunting (very short stature) and micronutrient deficiencies, are common in young children living in the developing world. Although families with children in the United States may suffer from food insecurity, due to government entitlement programs, severe, chronic hunger is very rare. Crying is at its height during early infancy and declines around month 4 as the cortex develops. Colic, excessive crying that disappears after early infancy, is basically a biological problem. Strategies for quieting crying babies include rocking, holding, and providing an outlet for the urge to suck. The skin-to-skin contact involved in infant massage, and kangaroo care, is preferable to swaddling, another classic technique. These practices may help infants—especially at-risk premature babies—grow.

Sleep is the basic newborn state, and from the 18-hour, waking-every-few hours newborn pattern, babies gradually adjust to falling asleep at night. REM sleep lessens and shifts to the end of the cycle. Babies, however, really do not ever sleep through the night. At about 6 months, many learn self-soothing, putting themselves back to sleep when they wake up. The decision about whether to “let a baby cry it out” or respond immediately at night is personal, because the best way to foster sleep is to provide a caring bedtime routine. Co-sleeping (or bed-sharing)—the norm in collectivist cultures—although still controversial in the West, is also a personal choice.

Sudden infant death syndrome (SIDS)— when a young baby stops breathing, often at night, and dies—is a main cause of developed-world infant mortality. Although SIDS may be caused by impairments in the developing fetal brain—it tends to occur most often when babies sleep face down. Therefore, a late-twentieth-century SIDS campaign urging parents to put babies to sleep on their backs (not stomachs) has been effective, although delivering this message is difficult in cultures that prize co-sleeping.

The preferential-looking paradigm (exploring what objects babies look at) and habituation (the fact that we get less interested in looking at objects that are no longer “new”) are used to determine what very young babies can see. Although at birth visual acuity is poor, it improves very rapidly. Face-perception studies show that newborns look at facelike stimuli, recognize their mothers, and even prefer good-looking people from the first weeks of life. At the same time that our visual capacities improve, due to neural pruning, we lose the ability to “see” facial differences we really don’t need. Sadly, this neural atrophy may bias us against other races. Depth perception studies using the visual cliff show that babies get frightened of heights around the time they begin to crawl.

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Infants’ bodies lengthen and thin out as they grow. The cephalocaudal, proximodistal, and mass-to-specific principles apply to how the body changes and emerging infant motor milestones. Although they do progress through stages when getting to walking, babies show incredible creativity and variability when they first attain skills. Reaching, in particular, literally opens babies up to encountering life. Earlier-than-normal motor development does not predict advanced cognition; but as babies get more mobile, parents need to discipline their children and baby-proof their home.

During Piaget’s sensorimotor stage, babies master the basics of physical reality through their senses and begin to symbolize and think. Circular reactions (habits the baby repeats) help babies pin down the basics of the physical world. Primary circular reactions—body-centered habits, such as sucking one’s toes—emerge first. Secondary circular reactions, habits centered on making interesting external stimuli last (for example, batting mobiles), begin around month 4. Tertiary circular reactions, also called “little-scientist” activities—like spitting food at different velocities just to see where the oatmeal lands—are the hallmark of the toddler years. A major advance in reasoning that occurs around age 1 is means–end behavior—understanding you need to do something different to get to a goal.

Piaget’s most compelling concept is object permanence—knowing that objects exist when you no longer see them. According to Piaget, this understanding develops gradually during the first years of life. When this knowledge is developing, infants make the A-not-B error, looking for an object in the place where they first found it, even if it has been hidden in another location before their eyes.

Using preferential looking, and watching babies’ expressions of surprise at impossible events, researchers now know that babies understand physical reality far earlier than Piaget believed. Because Piaget’s stage model also does not fit the gradual way cognition unfolds, contemporary developmentalists may adopt an information-processing approach, breaking thinking into separate components and steps. Scientists studying social cognition find that babies understand people’s motivations (and prefer people, based on judging their inner intentions) remarkably early in life.

Language, specifically our use of grammar and our ability to form infinitely different sentences, sets us apart from any other animal. Although B. F. Skinner believed that we learn to speak through being reinforced, the more logical explanation is Chomsky’s idea that we have a biologically built-in language acquisition device (LAD). Social-interactionists focus on the mutual passion of babies and adults to communicate.

First, babies coo, then babble, then use one-word holophrases, and finally, at 1 1/2 or 2, progress to two-word combinations called telegraphic speech. Caregivers naturally use infant-directed speech (exaggerated intonations and simpler phrases) when they talk to babies. Talking to babies in IDS is better than any baby-genius tape in promoting this vital human skill.