Developmental psychology is a broad field and it is difficult to cover all of the field in only two chapters. We teach 3 or 4 classes in order to cover the same material: child, adolescent, adult and aging psychology! Nonetheless it is one area of psychology which should appeal to everyone since we all develop.
There are 3 central issues in developmental psychology. The first (and most enduring and wide-reaching) is that of nature v. nurture. Which plays a bigger role: genetics or environment? It is a hotly debated topic and one that causes great controversy. To date, we do not know the exact contributions of each to any are of development. Some researchers may claim that 50% of intelligence is inherited but that is not a widely accepted fact. Be cautious about anyone who claims a certain percentage of any trait is due to either environment or heredity. Most psychologists acknowledge that most of development is a complex interaction between the two.
The second question is that of continuity versus stages. Does development occur in stages (as most developmental theories indicate) or is it continual? Stages development refers to qualitative stages that differ from one another and are usually age-linked. Timing may vary but everyone goes through the same stages in the same order.
The third big question is that of stability versus change. Do we change as we get older or are our personalities and other traits relatively set once we near adulthood? This question is most pertinent in terms of personality.
The first elements of development are motor and physical development and cognitive development. Motor and physical development follow well-documented stages. As infants there are some ranges for normal development but we mostly perform certain tasks at the same ages. Physical development is also important during adolescence when puberty becomes an issue. The range of normal development for puberty is quite wide. In older aging we also see the importance of physical elements. Notice that not all aging is primary and inevitable. Many physical characteristics of aging are considered secondary or the result of lifestyle. Again, there is a wide range of normalcy.
Cognitive development follows physical development. The two are linked since our cognitive development depends upon brain maturation. We cannot perform certain tasks until out brain has matured, myelination has occurred, and the neural connections have been made. The most prominent psychologist in terms of cognitive development is Jean Piaget. Piaget developed a theory of cognitive development which is based on maturation. It is a stage theory and is widely accepted. Each stage is qualitatively different from the previous one. We must develop the skills in one stage before proceeding to the next one. Current research indicates the Piaget underestimated the ages at which children accomplish these tasks. However, the ages at which children enter the stages is not too far off. And we can only help children advance so fast. Thus a seven year old is not capable of abstract thought which Piaget says is characteristic of adolescence.
Two other aspects of development are social and emotional. Many people consider these elements to be the main focal points of development. Within these areas we look at topics such as moral development and social development. Some of the theorists most prominent in this arena are Erik Erikson, Kohlberg and Gilligan.
Erik Erikson's theory is called psychosocial development. He began as a confederate of Freud but split since he saw development as spanning the entire lifespan and the social aspects of development as critical. He posed 8 stages and talks of a crisis at each stage which must be resolved. The term crisis is not used in the same way that we use the word. It refers to a conflict or an issue that must be resolved. For instance, Erikson talks of identity v. role confusion in adolescence. That is, the identity crisis that we all think of as representative of adolescence. James
Marcia expands upon the issue of identity in adolescence. Stages build one upon another and the crisis must be resolved successfully if the next stage/crisis is to be resolved.
Lawrence Kohlberg studied moral reasoning and has the most widely studied theory of moral development. His theory is predicated upon successful cognitive development (Piaget's theory). His is also a stage theory. Critics of Kohlberg maintain that his theory applies to Western males since his theory was developed by studying males at Harvard in the early 1960s. Other criticisms include that fact that it is a theory of moral reasoning, not moral action. Women tend to score at lower levels on tests of Kohlberg's theory.
Carol Gilligan disputes Kohlberg's theory since she claims that women work from a perspective of relationships and caring rather than justice which is the foundation of Kohlberg's theory.