THEORIES AND METHODS IN DEVELOPMENT STUDIES

Developmental psychology is the scientific study of how and why human beings change over the course of their life. Originally concerned with infants and children, the field has expanded to include adolescence, adult development, aging, and the entire lifespan.

The study of developmental psychology is essential to understanding how humans learn, mature and adapt. Often developmental psychology is thought of as only studying children. The early years of life is when many new developmental events occur, but developmental psychology is not only interested in childhood. Developmental psychology is broader than that, as developmental psychologists are interested in changes across the entire lifespan.

The two main processes that cause individuals to change across their lifetimes are maturation and learning. Maturation refers to developmental changes that occur as a result of the aging process, not from injury, illness or other life experience, including learning. Maturation information is encoded in an individual's genes. On the other hand, learning is a relatively permanent change in behavior (or potential behavior) as a result of experience or practice.

Throughout their lives, humans go through various stages of development. Developmental psychologists study how people grow, develop and adapt at different life stages. They conduct research designed to help people reach their full potential. Child development that occurs from birth to adulthood was largely ignored throughout much of human history.

Children were often viewed simply as small versions of adults and little attention was paid to the many advances in cognitive abilities, language usage, and physical growth that occur during childhood and adolescence.Interest in the field of child development finally began to emerge early in the 20th century, but it tended to focus on abnormal behavior. Eventually, researchers became increasingly interested in other topics including typical child development as well as the influences on development.

THEORIES OF CHILDHOOD

In the past, few distinctions were made between childhood and adulthood. In the 17th and 18th century, schooling was introduced for children, because it was recognized that an educated population would benefit society, as people would be a better labour force.

Thomas Hobbes believed that children are guilty of original sin, as they were intensely selfish egoists, so society must control them.

Jean Jacques Rousseau on the other extreme believed that children have an intuitive sense of right and wrong - or innate purity - and that sense is only misdirected by society. One suggestion is that Rousseau believed children were "noble savages."

John Locke on the other hand suggested that people are born with no tendencies at all - that is, newborn children have minds like tabula rasas or blank slates just waiting to have information written on them.

DEVELOPENTAL PSYCHOLOGY METHODOLOGY

Theories are all fine and good, of course, but psychology wants data to support whatever theory is being expounded. None of Hobbes, Rousseau, or Locke ever collected data that would support their theories of what humans are like when they enter into the world. To examine people at different ages, developmental psychologists do either cross-sectional or longitudinal studies.

Cross-sectional studies involve looking at different people at different ages. So, you could examine different individuals at 4 years of age, 6 years, and 8 years.

Longitudinal studies involve looking at the same people at different ages. So, you could look at the same individuals when they are 4 years old, when they are 6 years old, and when they are 8 years old.

One problem with cross-sectional studies is that it can be unclear whether the results are a matter of age differences or of differences in the experiences that group of people have experienced. Cohorts are groups of people who share similar experiences. Differences between groups of people who are different ages could be the result of cohort differences, which would be from cultural and historical factors they experienced growing up, rather than actual developmental change.

For example, a study of computer skills in 8 year olds and 12 year olds may find no differences. That result would be surprising, as it suggests that between age 8 and age 12 no improvement in computer skills is made. However, it could be that the 8 year olds were exposed to computers sooner than the 12 year olds, so they have just as much experience with computers as the 12 year olds; hence, we find no difference in computer skills, because the two age group cohorts were introduced to computers at different ages.

Thus, cross-sectional studies confound age and cohort effects, which makes it impossible to determine whether the results are due to age of the different individuals in each group (or cohort) or the experiences of the different individuals in each group (or cohort).

Longitudinal designs do not confound cohort and age, because the same individuals are being examined at each age. A problem with longitudinal designs is that they can take a long time to do. You may not have the time or inclination to wait for an answer to your hypothesis. Also, over time, the research techniques may improve, but you would be stuck using the old (inferior) techniques, because your results would be confounded by a change in technique.