Adolescence: Body, Brain, and Reasoning

This is Unit Nine, part two, on sexual health, adolescent thinking, and risk. Part one answered one question about risk with hot and cold decisions. Part two begins with sexual health, then turns to how adolescents think, and weighs the rival explanations of why they take risks. Carry one question through this part: which accounts of adolescent thinking and risk hold up under evidence? Piaget's final stage holds in part. Invincibility, a popular explanation, fares worse. At the entry that weighs why teens take risks, the part's answer is that no single cause explains it. By the end you will be able to define affirmative consent and name three models of sex education. To describe formal operations and the pendulum task. To tell the imaginary audience from the personal fable. To state the main criticisms of formal operations. And to weigh three explanations of teen risk taking.

Seven entries on sexual health: infection, violence, pregnancy, sex education, and consent.

Infections, and disease.

HGD 1230 STIs and STDs

A sexually transmitted infection is an infection passed through sexual contact by a virus, bacterium, fungus or parasite; it becomes a sexually transmitted disease when it produces disease. HPV and chlamydia are often carried without symptoms, so a person can transmit an infection without knowing it.

Sexual violence, as students report it.

HGD 1231 Sexual Violence

In twenty twenty-one, eleven percent of US high-school students reported sexual violence: eighteen percent of girls and five percent of boys, with higher rates among American Indian and Alaska Native, multiracial and LGBTQ+ youth. These figures are students' own reports in a national survey.

Early first intercourse.

HGD 1232 Early First Intercourse

Early first intercourse is linked to negative sexual-health outcomes and predicted by early puberty, adverse childhood experiences, drug use, family conflict and low parental support. Protective factors include higher family income, religious affiliation, sex education, parental monitoring and reproductive knowledge; religiosity delays first intercourse, especially for males.

Adolescent pregnancy.

HGD 1233 Adolescent Pregnancy

About three-quarters of teen pregnancies are unplanned, and about half of teen mothers finish high school by twenty-two, against about ninety percent of women without a teen birth. Sons of teen fathers are almost twice as likely to become teen fathers themselves. Teen parenthood is linked to lower education and earnings, though some teens are motivated by parenthood.

A falling teen birth rate.

HGD 1234 The Falling Teen Birth Rate

The US teen birth rate has fallen since nineteen ninety-one, reaching twelve point six births per thousand females aged fifteen to nineteen in twenty twenty-four, a decline spanning every racial and ethnic group tracked. Likely causes include contraception, sex education, access to family planning and less sexual activity.

Three models of sex education.

HGD 1235 Sex Education Models

US sex education follows three models: abstinence-only; abstinence-plus, which adds contraception information; and comprehensive, covering development, relationships, consent and identity. A review of three decades of research by Goldfarb and Lieberman linked comprehensive programmes to fewer births and infections. The course reports the review and takes no position on curriculum policy.

Affirmative consent.

HGD 1236 Affirmative Consent

Affirmative consent, yes means yes, is consent that is freely given, reversible, informed, enthusiastic and specific. US high-school students view it favourably, girls and teens with egalitarian gender views more so. Consent culture frames sexual activity as requiring clear agreement from every person involved, at every stage.

Four entries on formal thought: Piaget's final stage, its classic task, and the abstract and idealistic thinking that comes with it.

Piaget's final stage.

HGD 1237 Formal Operations

Formal operations, Piaget's final stage from about eleven or twelve, bring reasoning with logic and symbols about possibilities, including situations that do not exist, like a fourteen-year-old reasoning about how history would differ had a war gone the other way. Formal thinkers reason from imagined premises, not only from what they observe.

The pendulum task.

HGD 1238 The Pendulum Task

In Inhelder and Piaget's pendulum task, children discover which factor, string length, weight, drop height or push, governs how fast a pendulum swings. A concrete thinker changes everything at once; a formal thinker varies one factor at a time. Most children under twelve run biased experiments and conclude whatever they already believed.

Abstract and relativistic thinking.

HGD 1239 Abstract and Relativistic Thinking

Abstract ideas such as justice and truth gain importance in adolescence, along with relativistic thinking, seeing that many truths depend on the observer's position, as when a student weighs a dress code's fairness against the class time it costs. Seeing several dimensions at once also leads teens to question rules that seem arbitrary.

Adolescent idealism.

HGD 1240 Idealism

David Elkind described adolescent idealism: new analytic power makes teens critical of adult hypocrisy and the world's problems, with an urge for immediate change, like a fifteen-year-old pointing out that her parents ask her to recycle but drive everywhere. The accompanying de-idealization of parents and authorities is normal.

Three entries: two fables of the adolescent self, an audience made real online, and what survives of Piaget's final stage.

Two fables of the adolescent self.

HGD 1241 Adolescent Egocentrism

David Elkind described adolescent egocentrism in two parts. The imaginary audience is the belief that others are as focused on one's appearance and behaviour as one is oneself: a thirteen-year-old refuses to go to school over a small stain, sure everyone will notice. The personal fable is the belief that one is unique and special, so that others cannot understand one's feelings. The invincibility fable, a later label for part of the personal fable, is the belief that nothing can cause one harm. Exam items describe the belief and ask for the term: being watched is the imaginary audience; being uniquely misunderstood is the personal fable. Whether invincibility explains risk taking is contested, as this part's payoff shows.

The imaginary audience, online.

HGD 1242 The Imaginary Audience Online

Social media can make the imaginary audience feel real, since posts do attract watchers, and it can encourage risky self-disclosure, like a teen deleting a photo after an hour because it received too few likes. Adults active on social media also report feeling under scrutiny, so the effect is not unique to teens.

Piaget's final stage, weighed.

HGD 1243 Evaluating Formal Operations

Piaget's account of formal operations has held up in part and been challenged in part. What holds: adolescents gain the capacity to reason about possibilities, to test hypotheses systematically, and to handle abstract ideas. What has been challenged comes in four parts. Development is less stepwise than stages imply: a teen may reason formally in one domain and concretely in another. Piaget underplayed culture and social interaction, which Vygotsky stressed. Relying on verbal explanations can confuse performance with competence. And treating formal operations as the endpoint reflects a bias toward WEIRD societies; other cultures value wisdom, art and practical success. The misconception is that everyone reaches formal operations. It depends on schooling and on whether a culture emphasizes scientific reasoning, and many adults use it inconsistently. The stage describes a capacity many adolescents develop, not a guarantee.

Four entries on processing speed, two kinds of risk taking, culture's imprint on thinking, and parenting for school.

Perceptual speed and metacognition.

HGD 1244 Perceptual Speed and Metacognition

Perceptual speed, rapid recognition of objects and symbols, peaks in late adolescence and then declines, and it predicts job and school performance. Metacognition, planning, monitoring and judging one's own learning, develops through adolescence and plateaus in adulthood, as teens learn to reject misleading advice while accepting good advice.

Two kinds of risk taking.

HGD 1245 Reasoned and Reactive Risk Taking

Many teen risks are planned rather than impulsive, like a teen who researches a skateboarding trick for weeks before trying it. Reasoned risk takers show more sensation seeking, better working memory and more future orientation. The misconception is that every teen risk is impulsive; reasoned and reactive risk taking are distinct.

Culture and adolescent thinking.

HGD 1246 Culture and Adolescent Cognition

Culture shapes cognition: in a study by Masuda and Nisbett, Japanese participants encoded objects together with their backgrounds, while Americans encoded objects apart from context. Chinese fraction names, of four parts, one, may ease fraction learning. In cultures that do not emphasize scientific reasoning, formal operations may not be observed at all.

Parenting and school performance.

HGD 1247 Parenting and School Performance

Authoritative parenting, warm and firm with explained rules, best supports adolescents' school performance and engagement, in research by Steinberg and colleagues. Home learning resources, books, a quiet place to study, a computer, vary with family income. Curricula track cognitive growth, introducing abstract subjects such as algebra as formal reasoning becomes possible.

Six entries on reward and risk, including three rival explanations weighed side by side. The opening question is answered here.

Sensitivity to reward.

HGD 1248 Reward Sensitivity

Adolescents are more sensitive to reward cues than children or adults, as changes in the brain's dopamine system raise sensation seeking and reward motivation; the nucleus accumbens, a reward centre, is active when a teen anticipates a prize. Dopamine is a neurotransmitter, not a hormone, and accounts of its role in adolescence remain hypotheses.

The dual systems model.

HGD 1249 The Dual Systems Model

Steinberg's dual systems model holds that the reward system matures earlier than the prefrontal control system, opening a window of vulnerability to risk in middle adolescence: in Steinberg's image, a powerful engine engaged before the braking system is in place. The model is influential and contested, as this part's payoff weighs.

Peers, and social reward.

HGD 1250 Peers and Social Reward

Pubertal rises in oxytocin make social connection more rewarding, and peer approval becomes as rewarding for teens as money or food. Teen drivers make riskier decisions with friends in the car, to impress them, and teens are much more likely than adults to commit crimes in groups rather than alone.

What teens know about risk.

HGD 1251 Teens Know the Risks

Adolescents perceive the riskiness of choices about as accurately as adults do; they weigh rewards more heavily, especially with peers present. A teen who can list every danger of drunk driving may still get into a friend's car after a party. The misconceptions are that teens feel invincible or do not know the dangers; awareness alone changes little.

The payoff: why teens take risks.

HGD 1252 Why Teens Take Risks

Three explanations compete for why adolescents take more risks, and weighing them answers this part's question. The oldest is Elkind's personal fable: teens feel invincible. But adolescents judge riskiness about as accurately as adults do. The second is informational: teens do not know the dangers. The same evidence undercuts it, so awareness-only programmes are expected to help little, as Steinberg has argued. The third is Steinberg's dual systems model: reward systems mature before prefrontal control, and peers amplify the imbalance; the same sixteen-year-old drives carefully alone and recklessly with three friends. The model fits better but is contested, because much teen risk taking is reasoned, with better working memory and future orientation. No single cause explains teen risk. And brain differences correlate with behaviour; explaining everyday choices from brain images is an inference.

Risky driving.

HGD 1253 Risky Driving

In twenty nineteen, forty-three percent of US high-school students did not always wear a seat belt, and thirty-nine percent of drivers texted or emailed while driving; nearly seventeen percent rode with a driver who had been drinking. Accidents are a leading cause of adolescent death, which makes these habits especially consequential.

Three entries to close the unit, on delinquency and substance use, and on a decline that missed one group.

Delinquency.

HGD 1254 Delinquency

Delinquency is an unlawful act committed by a minor. It has been declining, though about thirty-four percent of adolescents report some criminal behaviour in one survey. Risk factors include low monitoring, parent–teen conflict, absenteeism, dropout, poverty, dangerous neighbourhoods and maltreatment, and multisystemic therapy reduces reoffending.

Substance use in adolescence.

HGD 1255 Substance Use in Adolescence

In twenty twenty-three, about twenty-two percent of US high-school students drank alcohol and seventeen percent used marijuana in the past month, according to the CDC, and prescription-opioid misuse was reported by fourteen percent of girls and nine percent of boys. Risk factors include availability, poor parent relationships, family and peer use, and insufficient sleep.

The great decline.

HGD 1256 The Great Decline

Adolescent substance use has declined since twenty nineteen for most groups, a trend researchers call the great decline, though not among LGBTQ+ youth. Proposed explanations include less unstructured time with peers, changing norms and pandemic-era supervision. Among LGBTQ+ youth, victimization predicts substance use, which helps explain why their rates have not fallen.

Look at what you can now do. You can define affirmative consent, freely given, reversible, informed, enthusiastic and specific, and name the abstinence-only, abstinence-plus and comprehensive models. You can describe formal operations, reasoning about possibilities, and the pendulum task, where a formal thinker varies one factor at a time. You can tell the imaginary audience, feeling watched, from the personal fable, feeling uniquely misunderstood. You can state the criticisms of formal operations: less stage-like, culturally bounded, and not universal. And you can weigh the explanations of risk: invincibility and ignorance fit the evidence poorly, reward and peers fit better, and no single cause explains it all. Unit Ten turns to identity and relationships.