If one is not developing in a healthy and positive manner throughout life, it is possible to become completely self-possessed during middle age. Instead of expressing concern about the people and society around them and their relationship with others, the middle-aged person is completely selfish and out to satisfy their own desires without much consideration for anyone else.

Jean Piaget set the intellectual foundations for Kohlberg's six stages of moral development. The major difference is that Piaget elucidates the process of moral reasoning in children, rather than breaking down moral development into evolutionary stages. Piaget said that children approach problems in two different ways: assimilation and accomodation. In assimilation, children easily internalize the rules of the outside world, including the ethical ones. In accomodation, children may have to change these internalized ideas or other pre-existing notions to fit what they see in the world. Kohlberg expanded on this and categorized ideas based on the stages of a person's life which, according to him, define the moral dilemnas a person faces.

In the presence of a Y chromosome, testosterone prevents the default female organs from developing in the embryo. However, to prevent female organs from developing and to initiate development of male reproductive organs, testosterone must be received by 5-alpha reductase receptors. If testosterone is present, but there are no receptors, female organs will continue to develop in spite of the Y chromosome. This is called 5-alpha reductase deficiency. Although genetically male, the baby has the appearance of a female. In many cases however, a surge of testosterone during puberty leads to development of male reproductive organs.

The Sensorimotor stage ranges from zero to two years of age. The phrase “out of sight, out of mind” describes a child before developing true object permanence. True object permanence is the ability of a child to know that even though an object is not visible to them, it still exists (imagine a game of peek-a-boo). In this stage, Piaget also proposed instinctual reflexes, intentional-ism, and coordination of speaking, hearing, and acting.  

Secondary sex characteristics are traits that develop during puberty, and include facial hair, enlarged breasts, pubic hair, and deeper voices. Primary sex characteristics are innate and include sex organs (the ovaries in women and testes in men) and genitalia. 

Longitudinal research is a popular method of conducting developmental psychology studies. This method takes one group of people and tracks the effect of the developmental factor being studied on them over time. This is a time-consuming and often tricky method of research and many researchers may turn to cross-sectional research instead.

Mary Ainsworth's study of attachment styles in parent-child relationships showed that babies with secure attachments to their parents would be distressed when their parents left the room and look for their comfort upon return. Ainsworth held that the baby had unconsciously recognized and accepted their dependence on their caregivers for their needs. The other attachment styles identified in the study were avoidant and anxious/ambivalent, where the babies may not have felt they could depend on their caregivers to fulfill their needs.

Permissive parenting is the most "relaxed" of the parenting styles. It's defined by a lack of consistency in rules and consequences that are usually not enforced, or are enforced in an inconsistent manner. Permissive parenting is on the opposite end of the spectrum from Authoritarian parenting, which features extremely strict rules with strong enforcement of punishment, and little explanation. Most parenting styles fall somewhere between these two polarized points on the spectrum of parenting style.

Authoritarian parents typically create strict rules that are not open to being updated based on the child's input. These parents have high expectations for their children, and are usually not nurturing. 

FAS is a rare, serious, and irreversible disorder that is caused by heavy drinking by the mother during pregnancy. Although FAS is more common than some other results of substance abuse during pregnancy, it is not the only one- there are damaging effects of cocaine use during pregnancy, for example. FAS presents a number of symptoms including low birth weight, malformed skulls, and intellectual disabilities and its effects present immediately.