Summary

1. Instinct and innate are vague, rarely defined terms that fail to recognize that all behaviors are influenced by genes and that every behavior can be modified by experience. A more useful criterion to designate more complex behaviors is to ask whether they require social interactions during development to properly unfold. In many species, especially those that require parental care, many behaviors are lost or severely distorted without social experience. See Figures 10.1 and 10.2
2. In mammals and birds, parental care is required for survival. Rat maternal care can reduce methylation of the glucocorticoid receptor gene in the brain, resulting in offspring that have a less severe stress response as adults. Female rats reared by an attentive dam are more likely to be attentive to their own pups in turn. The altered methylation of the glucocorticoid receptor gene caused by maternal care is sometimes called an epigenetic effect, but there are inconsistencies in the use of this term, as with instinct and innate. See Figures 10.3 and 10.4, Box 10.1
3. Sudden infant death syndrome (SIDS), the unexplained respiratory failure of infants, is less common among babies who are placed on their backs to sleep. Interestingly, those babies are also slightly delayed in reaching milestones in motor development, presumably because they have less experience on all fours. See Figure 10.5
4. Young birds imprint on the first slowly moving object they see, which is typically their mother. In many species, adults will attempt to mate with animals resembling the birds that reared them as chicks, a result of sexual imprinting. Young birds appear to learn the safest migratory route by accompanying older birds. See Figures 10.6–10.8
5. Many examples of observational learning have been documented in the wild, including monkeys dipping yams in water, birds raiding milk bottles, and birds attacking hibernating bats or surfacing whales. We have no way of knowing what other foraging behaviors of animals originated in such innovations that spread by observational learning. See Figure 10.9
6. In many songbird species, males memorize the song they hear as nestlings, whether of their biological father or a foster father, and later produce a variant of that song as their own. The young males first produce plastic song and then, guided by auditory feedback and memory of the song they heard as nestlings, fine-tune their own song, which is then said to be crystallized. Birds are predisposed to incorporate elements of the song of their own species rather than that of other species. See Figures 10.10–10.13
7. The FOXP2 gene appears to be important for vocal communication, as it is important for birdsong learning and ultrasonic vocalization in rodents, and mutant alleles of the gene result in specific language deficits in humans. In contrast, people with Williams syndrome are verbally fluent but may otherwise be mentally impaired. See Figure 10.14
8. Children reach language milestones in a relatively fixed sequence. Across cultures, people speak parentese to babies. Newborns appear to be capable of discriminating all the known phonemes that occur in human languages, but as they grow, they become better at discriminating the phonemes they hear and may lose the ability to discriminate other phonemes. See Figures 10.15 and 10.16, Table 10.1
9. The loss of the ability to discriminate phonemes not heard in infancy makes it more difficult for adults to learn additional languages and may have contributed to the progressive loss of phonemes in languages as humans migrated across the globe. See Figures 10.17 and 10.18
10. Monkeys raised without a live, interactive mother, which Harry Harlow regarded as a source of love, display very abnormal behavior as adults; essentially they are unable to socially interact with others. Growing up with peers ameliorates much of the behavioral consequences of being motherless. Children who form a secure attachment to a caregiver have healthier, more positive social interactions as adults. See Figure 10.19
11. Social isolation during the juvenile period has wide-ranging effects on development of the brain and behavior, including stunted expression of neuregulin, resulting in reduced myelination. See Figures 10.20–10.23
12. Scores on IQ tests of abstract reasoning positively correlate with health, longevity, and success in school and the marketplace. Nevertheless, people with IQs between 95 and 110 can be found in almost any profession. The Flynn effect is the progressive improvement seen across the world in IQ performance since the tests began, which cannot be accounted for by changes in the genome. See Figures 10.24–10.26
13. Comparison of relatives demonstrates that genes influence IQ performance. However, environmental factors, including socioeconomic status (SES) and exposure to toxins like lead, also influence IQ. See Figures 10.27 and 10.29
14. Differences in average IQ scores across human groups may be due, in part, to the effects of stereotype threat for African Americans. The difference in average IQ between white and black Americans shrank dramatically in the first half of the twentieth century, and it appears to be shrinking still. Among children born to women in 1950s Germany and raised there, those fathered by black American servicemen scored as high on IQ tests as those fathered by white Americans. See Figures 10.28 and 10.30