What Is Attachment?
The first section of the chapter explores social development at the time of infancy. Many young animals must be cared for by the older members of their species. The importance of this is seen in the instinctual behavior of imprinting in various bird species, by which they will attach themselves to a mother figure about 18 hr after hatching. Harry Harlow also showed the importance of attachment in his classic studies with rhesus monkeys, in which they preferred a terry-cloth mother over one that dispensed food.

The idea of attachment in humans was popularized by John Bowlby, who conceptualized it as an adaptive strategy to keep infants and caregivers in close contact. Mary Ainsworth developed a means for assessing the caregiverÂinfant bond and identified three styles of attachment: secure, avoidant, and anxious-ambivalent. This has proven to be a fruitful area of investigation, and each attachment style is associated with later behaviors. Finally, it appears that there is a physiological basis to attachment behaviors. The hormone oxytocin promotes numerous maternal tendencies that are associated with the survival of the infant.

Who Influences Social Development
As the child develops, a wider range of behaviors must be addressed than those that ensure survival. Parents have long wondered what contributes to successful social development in their children. Chess and Thomas found that the fit between the childĦs temperament and the parentsĦ behaviors is most important in determining social development. The implication of this is that there is no one way to raise children and that parents must be sensitive to each childĦs unique needs.

As children grow, peers become more important in their lives. Judith Rich Harris made quite an impact in 1995 with her group socialization theory, which suggested that parents have very little affect on their childĦs social development. Other researchers have been critical of this overstatement and presented data showing that both parents and peers are important. The value of friends continues through adulthood, although the nature of these friendships appears to differ between the sexes. WomenĦs same-sex friendships are characterized more by emotional disclosure about personal issues, whereas men tend to participate in shared activities with other men. Both sexes report more friendships with the same sex as, apparently, the potential for intimacy between cross-sex friends inhibits their development.

How Does Moral Behavior Develop?
The next section of the chapter involves the critical role that morality plays in social development. As humans began to live in larger groups, it became increasingly important that they considered the effect of their actions on others and on the maintenance of social contracts. The authors divide moral development into cognitive and affective components. The cognitive component of moral reasoning has been investigated by the well-known stage theory of Lawrence Kohlberg, who classified individuals at different levels of moral reasoning (preconventional, conventional, postconventional) based on their answers to moral dilemmas. The moral emotions of empathy, sympathy, guilt, and shame provide an interesting insight to moral behavior. Again, these emotions appear to be adaptive in that they remind us of social contracts and encourage behaviors consistent with social norms.

Some investigators believe it is the experience of emotions produced by rewards and punishments that facilitates moral actions. As was discussed with Damasio's somatic marker hypothesis in Chapter 10, the visceral response associated with emotions has a tremendous influence on decision making. Recent results from behavioral neuroscience also support the idea of a physiological component to moral emotions and behavior.

What Influences Gender Development and Identity?
The brain changes throughout development and as a result of experience, a property known as plasticity. This plasticity allows the brain to recover some function after injury, though typically brain plasticity decreases with age. Changes in neuronal connections occur as a result of experience. This is the basis of learning. Neurons that fire together strengthen their connections with one another, increasing the likelihood that they will fire together in the future, a process known as Hebbian learning.

The final section of the chapter considers the issues of sex, gender, and gender identity. There are clear biological differences between the sexes. However, recent research suggests that gender identity, one's sense of being male or female, is the result of a combination of biological, social, and cultural forces. Gender roles, the behaviors that differ between men and women, are clearly determined by cultural norms. One's sense of identity was addressed by Erik Erikson in his psychosocial theory of development. Erikson thought that we developed in stages and that a new developmental crisis needed to be confronted at each stage. If the crisis is handled appropriately, then psychosocial growth occurs.

Table 12.1: Erikson's Developmental Crises
Age	Psychosocial Crisis	Appropriate Resolution
0-1.5 years	trust vs. mistrust	strong ties with caregivers
1.5-3 years	autonomy vs. doubt	self-reliance, exploration
3-5 years	initiative vs. guilt	self-control, planning, responsibility
Grade school	industry vs. inferiority	personal efficacy
Adolescence	identity vs. confusion	sense of values and beliefs
Young adult	intimacy vs. isolation	committed friendships, romantic relationships
Middle adult	generativity vs. stagnation	producing, giving back to society
Older adult	integrity vs. despair	positive reflections

The issue of one's identity was further explored by James Marcia, who viewed identity formation as involving crisis and commitment. Marcia envisioned four possible outcomes or statuses to these crises: identity achievement, identity foreclosure, identity moratorium, and identity diffusion. A similar stage theory for the formation of one's ethnic identity (unexamined stage, exploration stage, achievement stage) was proposed by Jean Phinney.