Adolescence
The average age of onset for puberty is 10 to 11 years for girls and 11 to 12 years for boys. This biological process triggers a surge in hormone production that initiates a chain reaction throughout the body. The pituitary gland secretes hormonal agents into the bloodstream, activating the testes or ovaries. Testes primarily release testosterone while ovaries predominantly dispense estrogen. These hormones increase gradually until sexual maturation is met. Facial hair in males typically appears between 14 and 17 years of age at the corners of the upper lip first. It then spreads to form a moustache over the entire upper lip before appearing on the cheeks and chin. The major landmark of puberty for males is spermarche, which occurs on average at age 13. For females, menarche marks the onset of menstruation between ages 12 and 13. Girls who have a high-fat diet and are not physically active begin menstruating earlier than those with less fat diets. Nearly half of all American high school girls' diets aim to lose weight. Early maturing boys often appear taller and stronger than their friends but may face increased social pressure to conform to adult norms. Early maturing girls can become more insecure and dependent due to their bodies developing in advance. They are more likely to develop eating disorders such as anorexia nervosa. Girls usually reach full physical development around ages 15 to 17 while boys complete puberty around ages 16 to 17.
The human brain reaches 90% of its adult size by six years of age. Over the course of adolescence, white matter increases linearly while grey matter follows an inverted-U pattern. Synaptic pruning eliminates unnecessary neuronal connections to make the brain more efficient through myelination. The first areas pruned involve primary functions like motor and sensory areas. Complex processes lose matter later including the lateral and prefrontal cortices. Changes in the dorsolateral prefrontal cortex control impulses and planning ahead. Ventromedial prefrontal cortex development aids decision making. Orbitofrontal cortex changes evaluate rewards and risks. Glutamate is an excitatory neurotransmitter whose receptors are found on most neural connections pruned during this period. Dopamine levels increase in the limbic system during adolescence. This balance of excitatory to inhibitory neurotransmitters may imply adolescent risk-taking and vulnerability to boredom. Serotonin regulates mood and behavior with gene expression changing dramatically in the frontal cortex. Adolescents become more emotional and responsive to rewards and stress due to these shifts. The effect of serotonin extends beyond the limbic system into the human frontal and prefrontal cortex. Prefrontal cortex pruning has been recorded to level off by age 14 or 15 but continues as late as into the sixth decade of life.
Adolescents' thinking becomes less bound to concrete events than that of children. They can contemplate possibilities outside the realm of what currently exists. Deductive reasoning improves leading to hypothetical thinking that allows planning for future consequences. Adolescents find it easier to comprehend higher-order abstract logic inherent in puns, proverbs, metaphors, and analogies. Children younger than age nine often cannot comprehend sarcasm at all. Metacognition involves monitoring one's own cognitive activity during the thinking process. It leads to better self-control and more effective studying. Adolescents are much better able than children to understand that people do not have complete control over their mental activity. Being able to introspect may lead to two forms of adolescent egocentrism: the imaginary audience and the personal fable. These likely peak at age fifteen along with general self-consciousness. Perspective-taking involves a more sophisticated theory of mind where adolescents understand how thoughts influence others even if they are not involved. By ages 12 to 14 critical thinking and decision-making competency become comparable to those of adults. Processing speed improves sharply between age five and middle adolescence before leveling off at age 14 or 15. White matter is recorded to increase up until around the age of 45 then lost via progressive aging.
For most individuals the search for identity begins in the adolescent years. Adolescents cycle through different behaviors and appearances to discover who they are. Erik Erikson argued that not everyone fully achieves identity despite having a self-concept. Identity represents a coherent sense of self stable across circumstances including past experiences and future goals. James Marcia developed a method testing progress through occupation, ideology, and interpersonal relationships categories. His questions classify individuals into identity diffusion, identity foreclosure, moratorium, or identity achievement. Research since reveals self-examination beginning early but identity achievement rarely occurring before age 18. The freshman year of college influences identity development significantly by encouraging reexamination of previous commitments. Fashion plays a major role when teenagers find their selves as it evolves with personality changes. Modern life takes place amidst a never-ending barrage of flesh on screens pages and billboards causing issues with self-image. A study of 194 lesbian gay and bisexual youths under age 21 found awareness of sexual orientation occurred on average around age 10. Coming out to peers and adults occurred around ages 16 and 17 respectively. The suicide rate amongst LGBT adolescents is up to four times higher than heterosexual peers due to bullying and rejection. Baseline self-esteem remains highly stable across adolescence even though barometric self-esteem fluctuates rapidly.
The formal study of adolescent psychology began with G. Stanley Hall's publication of Adolescence in 1904. Hall defined adolescence as the period from ages 14 to 24 viewing it primarily as internal turmoil and upheaval. His assertions stood relatively uncontested until the 1950s when psychologists like Erik Erikson and Anna Freud formulated their theories. Jean Macfarlane founded the University of California Berkeley's Institute of Human Development in 1927. The Oakland Growth Study initiated by Harold Jones and Herbert Stolz in 1931 aimed to study physical intellectual and social development. Data collection began in 1932 and continued until 1981 allowing researchers to gather longitudinal data extending past adolescence into adulthood. Glen Elder proposed a life course perspective of adolescent development in the 1960s. The principle of historical time and place states that an individual's development is shaped by the period and location they grow up in. In 1984 the Society for Research on Adolescence became the first official organization dedicated to studying adolescent psychology. Evolutionary biologists like Jeremy Griffith have drawn parallels between adolescent psychology and developmental evolution of modern humans from hominid ancestors.
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Common questions
What is the average age of onset for puberty in girls and boys?
The average age of onset for puberty is 10 to 11 years for girls and 11 to 12 years for boys. This biological process triggers a surge in hormone production that initiates a chain reaction throughout the body.
When does spermarche occur on average for males during adolescence?
Spermarche occurs on average at age 13 for males. It serves as the major landmark of puberty for boys while facial hair typically appears between 14 and 17 years of age.
At what age do adolescents reach full physical development compared to when they complete puberty?
Girls usually reach full physical development around ages 15 to 17 while boys complete puberty around ages 16 to 17. The human brain reaches 90% of its adult size by six years of age before white matter increases linearly over the course of adolescence.
How does identity achievement relate to age and self-examination in adolescent psychology?
Identity achievement rarely occurs before age 18 despite self-examination beginning early. Erik Erikson argued that not everyone fully achieves identity despite having a self-concept, and James Marcia developed a method testing progress through occupation ideology and interpersonal relationships categories.
What was the average age of first sexual intercourse reported in an American study from 2002?
An American study from 2002 reported the average age of first sexual intercourse was 17.0 for males and 17.3 for females. A separate study conducted by YouGov for Channel 4 found twenty percent of 14 to 17-year-olds surveyed revealed first sexual experience at 13 or under in the United Kingdom.
When did G. Stanley Hall publish his formal study defining adolescence as internal turmoil?
G. Stanley Hall published Adolescence in 1904 defining it as the period from ages 14 to 24 viewing it primarily as internal turmoil and upheaval. His assertions stood relatively uncontested until the 1950s when psychologists like Erik Erikson and Anna Freud formulated their theories.