<P> Given the potential consequences, engaging in sexual behavior is somewhat risky, particularly for adolescents . Having unprotected sex, using poor birth control methods (e.g. withdrawal), having multiple sexual partners, and poor communication are some aspects of sexual behavior that increase individual and / or social risk . Some qualities of adolescents' lives that are often correlated with risky sexual behavior include higher rates of experienced abuse, lower rates of parental support and monitoring . </P> <P> Related to their increased tendency for risk - taking, adolescents show impaired behavioral inhibition, including deficits in extinction learning . This has important implications for engaging in risky behavior such as unsafe sex or illicit drug use, as adolescents are less likely to inhibit actions that may have negative outcomes in the future . This phenomenon also has consequences for behavioral treatments based on the principle of extinction, such as cue exposure therapy for anxiety or drug addiction . It has been suggested that impaired inhibition, specifically extinction, may help to explain adolescent propensity to relapse to drug - seeking even following behavioral treatment for addiction . </P> <P> The formal study of adolescent psychology began with the publication of G. Stanley Hall's "Adolescence in 1904 ." Hall, who was the first president of the American Psychological Association, viewed adolescence primarily as a time of internal turmoil and upheaval (sturm und drang). This understanding of youth was based on two then new ways of understanding human behavior: Darwin's evolutionary theory and Freud's psychodynamic theory . He believed that adolescence was a representation of our human ancestors' phylogenetic shift from being primitive to being civilized . Hall's assertions stood relatively uncontested until the 1950s when psychologists such as Erik Erikson and Anna Freud started to formulate their theories about adolescence . Freud believed that the psychological disturbances associated with youth were biologically based and culturally universal while Erikson focused on the dichotomy between identity formation and role fulfillment . Even with their different theories, these three psychologists agreed that adolescence was inherently a time of disturbance and psychological confusion . The less turbulent aspects of adolescence, such as peer relations and cultural influence, were left largely ignored until the 1980s . From the' 50s until the' 80s, the focus of the field was mainly on describing patterns of behavior as opposed to explaining them . </P> <P> Jean Macfarlane founded the University of California, Berkeley's Institute of Human Development, formerly called the Institute of Child Welfare, in 1927 . The Institute was instrumental in initiating studies of healthy development, in contrast to previous work that had been dominated by theories based on pathological personalities . The studies looked at human development during the Great Depression and World War II, unique historical circumstances under which a generation of children grew up . The Oakland Growth Study, initiated by Harold Jones and Herbert Stolz in 1931, aimed to study the physical, intellectual, and social development of children in the Oakland area . Data collection began in 1932 and continued until 1981, allowing the researchers to gather longitudinal data on the individuals that extended past adolescence into adulthood . Jean Macfarlane launched the Berkeley Guidance Study, which examined the development of children in terms of their socioeconomic and family backgrounds . These studies provided the background for Glen Elder in the 1960s, to propose a life - course perspective of adolescent development . Elder formulated several descriptive principles of adolescent development . The principle of historical time and place states that an individual's development is shaped by the period and location in which they grow up . The principle of the importance of timing in one's life refers to the different impact that life events have on development based on when in one's life they occur . The idea of linked lives states that one's development is shaped by the interconnected network of relationships of which one is a part; and the principle of human agency asserts that one's life course is constructed via the choices and actions of an individual within the context of their historical period and social network . </P>

When was adolescence first considered a period of development