What's Going on in There?

Such adaptability is a property of the brain from its very first emergence. While genes program the sequence of neural development, at every turn the quality of that development is shaped by environmental factors. (Location 218)

Around two or three months after birth, activity levels shoot up in several cortical areas, most notably in the roughly rear half of the brain that controls visual perception. Then after six or eight months, the frontal lobe begins to rise in glucose utilization. Within the frontal cortex, phylogenetically older areas are activated before newer ones, which don’t register significant activity until the last few months of the first year. As we will see, frontal activation is responsible for the first inklings of higher cognitive function in babies, a surge in memory, emotion, and general awareness that takes off around eight months after birth. (Location 667)

According to one theory, the fatigue and nausea that many women suffer during early pregnancy are another means of protecting the embryo and young fetus. These symptoms peak during the baby’s most vulnerable phase, when all of its organs are first forming. Fatigue tends to keep a woman from risky physical activities, while “morning sickness” (a misnomer since it often lasts all day) tends to keep her diet bland, helping her to avoid natural toxins present in spoiled or exotic foods. Our best guess is that these symptoms are caused by the placental hormone human chorionic gonadotropin (HCG). This hormone can be detected in the mother’s blood as early as one week after conception (which is why its measurement is the basis of pregnancy testing in home kits). (Location 725)

It also varies with time of day, with the thinnest milk (the lowest fat content) being produced early in the day and the richest produced in the evening. Finally, it varies with the mother’s diet, providing breast-fed infants a rich medium for experiencing many different flavors in early life. (Location 3415)

Babies who recognize familiar stimuli more efficiently may therefore be better at building a vocabulary, solving problems, and using abstract reasoning during the preschool and early elementary school years. Infants with better recognition memory probably also benefit more from their early experiences, learning faster than babies with poorer recognition skill. So if you find yourself run ragged by a baby who seems to grow instantly bored with every new toy or variation on peekaboo, try to look on the bright side—it may mean you’ve got a budding Einstein on your hands. (Location 6206)

Parents who talk more inevitably expose their children to a greater variety of words and sentences, so a correlation also turned up between the diversity of parents’ language—the number of different nouns and adjectives they used, and the length of their phrases and sentences—and their children’s linguistic progress. In addition to these quantitative features, Hart and Risley discovered a particular qualitative aspect of parental language that seems to especially influence children’s language: the amount of positive versus negative feedback children hear. Youngsters who heard a larger proportion of no, don’t, stop it, and similar prohibitions had poorer language skills than three-year-olds who had received less negative feedback. Of course, no parent of toddler-aged children can avoid all prohibitions, but those who kept their negative responses to a minimum, emphasizing instead positive responses, such as repeating their children’s vocalizations or following them with questions or affirmations, fostered better language development. (Location 6966)