PS218 - T2W10 - Adolescence

This lecture covers adolescence — one of the most talked-about and misunderstood periods of human development. It's split into two main parts: the first looks at the physical, biological, and cognitive changes that happen during adolescence, and the second focuses on the social side — friendships, relationships with parents, and the development of identity. Together they paint a picture of adolescence not as some inevitable catastrophe but as a genuinely complex transition that most young people navigate pretty well.

So to start with — what even is adolescence? It's typically defined as roughly the period between 12 and 18 years old, but those boundaries are fuzzy and vary across cultures. It's marked by a combination of biological events (puberty, brain development) and social events (legal rights, educational transitions), and it's actually a relatively modern concept — the idea of adolescence as a distinct life phase didn't really exist in the same way historically and still doesn't take the same form in all cultures.

The physical transitions are probably what most people think of first. Puberty involves a growth spurt, and for girls the onset of menstruation (menarche), and for boys the production of sperm (spermarche). Interestingly, the timing of puberty matters a great deal for how adolescents experience it. Early maturing boys tend to do relatively well — they tend to have a more positive self-concept, be more popular, do better at sports, and achieve more at school. Early maturing girls, however, tend to have a harder time — they show more conflict with parents, higher rates of depression, less popularity, more risky behaviours, and more eating disorders. This is sometimes called the "maturational deviance hypothesis" — the idea that developing at a different time from your peers, especially earlier, is a source of stress. An important trend is that the average age of menarche has been declining over the last 150 years, likely due to improved nutrition, though family factors also play a role — girls from father-absent households tend to mature earlier. The social environment also shapes the impact of early maturation; for example, early maturation has stronger effects in mixed-sex schools than single-sex ones. Early maturation combined with rapid hormonal increases is considered the highest-risk combination.

Alongside puberty, the brain is also going through significant changes. Two key processes are happening. Myelination involves the coating of nerve fibres in a fatty sheath, which speeds up neural communication and increases what's called "white matter" in the brain. Meanwhile, synaptic pruning is happening — the brain is actually eliminating excess neural connections, leading to a decrease in "grey matter." This might sound counterintuitive (fewer connections sounds worse), but it's actually more like a brain becoming more efficient — cutting away the unused pathways and strengthening the ones that matter. Gogtay and colleagues (2004) produced averaged MRI scans from children aged 5 to 20 that visually showed this progressive decrease in grey matter across development. Hormones also interact with brain structure — they drive physiological changes, which drive changes in behaviour, which in turn modify brain structures. It's another example of how biology and environment shape each other.

Three theoretical models of adolescence are presented in the lecture, each offering a different lens. The first and oldest is the "storm and stress" model, attributed to G. Stanley Hall writing in 1904, who compared adolescent emotional states to being heated like wine. This model sees adolescence as a period of universal, biologically-driven turbulence — mood swings, conflicts, and risky behaviour. Arnett (1999) revisited this question and found that the evidence gives a more nuanced picture. Mood disruptions do occur in adolescence, and conflict with parents does increase, particularly in early adolescence. Risky behaviours do peak, but typically in late adolescence or early adulthood rather than the middle of the teenage years. The takeaway from Arnett (1999) is that storm and stress is likely but not inevitable — it's not a universal biological programme, and many adolescents move through this period without serious difficulty. The second model is developmental contextualism, associated with Bronfenbrenner (1979), which argues that you can't understand adolescent development without looking at the full ecology surrounding the young person — their family, school, community, culture, and the broader social context. Crucially, timing matters (the same event can affect people very differently depending on when it happens), adolescents actively shape their own environments (they're not passive recipients of development), and there needs to be a "goodness of fit" between the individual and their context. The third model is Coleman's focal model, which is perhaps the most optimistic. Coleman argued that most adolescents actually cope pretty well, and that concerns and issues tend to peak at different points across the adolescent years rather than all hitting at once. The key insight is that problems arise when multiple challenges come together simultaneously — dealing with puberty, changing schools, family conflict, and romantic relationships all at the same time is much harder than dealing with each in turn.

Now onto the cognitive transitions of adolescence, which are just as significant as the physical ones. Piaget described this as the shift from concrete operational thinking to formal operational thinking. Concrete operational thinking is tied to the here and now — reasoning about real, tangible things. Formal operational thinking is abstract — it can handle hypothetical situations, variables, and propositions that have no real-world referent. A simple example: in concrete operations you can work out that if Derrick is taller than Fiona and Fiona is taller than Elizabeth, then Derrick is tallest, because the problem is grounded in reality. In formal operations you can work out the same kind of problem even when the premise is absurd — "If ants are bigger than dogs and dogs are bigger than elephants, which is biggest?" — because you're reasoning with the logical structure, not the real-world content. Adolescents also develop hypothetico-deductive reasoning — the ability to think like a scientist. In concrete operations, a child might have one hypothesis and test it, ignoring counter-evidence. In formal operations, an adolescent can generate multiple hypotheses, devise tests for them, and update their theory when evidence contradicts it. The classic test of this is the pendulum problem, where the task is to work out what determines how fast a pendulum swings (it's the length of the string). A concrete operational child will test one variable at a time without a systematic plan; a formal operational thinker will systematically vary each factor while holding others constant.

However, Piaget's formal operations account has its critics. The findings haven't always replicated well, and not everyone reaches formal operational thinking — it doesn't seem to be universal in the way Piaget suggested. It also can't be the final stage of development, since reasoning continues to improve into adulthood. The role of experience and training is important — people tend to reason in formal operational ways in domains they know well, which suggests it's more domain-specific than Piaget's general stage theory allows. Flieller (1999) did a cross-generational comparison and found that 35% of 13 to 15-year-olds reached formal operational thinking in 1967, compared to 55% in 1996 — a significant increase that suggests environmental and cultural factors have a real impact, which isn't well accounted for by a purely biological stage theory.

Two alternative accounts of cognitive development in adolescence are also discussed. The information-processing view focuses on gradual improvements in processing capacity, attention, memory, and organisational strategies. Metacognition — the ability to reflect on and monitor your own thinking — also improves, allowing adolescents to take more information into account when solving problems. The executive control view focuses on changes in specific brain areas involved in emotional regulation, response inhibition, planning, and monitoring. Adolescents become progressively better at managing their own mental processes — deciding what information is relevant, choosing efficient strategies. However, executive control still requires knowledge, so development in this area is tied to what the adolescent has learned.

How do these cognitive changes feed into other areas of development? Elkind (1967) described a form of "adolescent egocentrism" that emerges from the new ability to think about what other people are thinking. The catch is that adolescents initially fail to differentiate between their own preoccupations and others' — they assume everyone else is as focused on them as they are on themselves. This produces two related phenomena. The "imaginary audience" is the feeling that you're always being watched and judged — which explains the intense self-consciousness, concern about appearance, and desire for privacy that are so characteristic of early adolescence. The "personal fable" is the belief that your own feelings and experiences are uniquely special and that no one else could possibly understand them — this is linked to the risk-taking behaviour of adolescence (it won't happen to me). By about age 16, adolescents become better at distinguishing their own perspective from others', and egocentrism gradually decreases. Cognitive development also supports more complex moral reasoning — adolescents can move into Kohlberg's postconventional level, reasoning about abstract principles of justice and ethics rather than just rules and authority. Political thinking also becomes more sophisticated, shifting from concrete authoritarian views (one leader who makes decisions) towards more abstract ideological thinking, though this is influenced by socioeconomic status and the political views of parents.

Moving into the second part of the lecture — the social world of adolescence. One of the most striking facts about adolescent social life is simply how much time is spent with peers. Research using the Experience Sampling Method — where participants report on their activity and mood at random points throughout the day — found that talking to friends is the primary activity of adolescents, and the time when they feel happiest. Time with peers increases steadily from childhood through adolescence, eventually exceeding time spent with any other social group. Time with family drops dramatically — from around 33% of waking time at age 10 to around 14% at age 18. There are also cultural differences: American and European adolescents spend 40 to 50% of waking hours on leisure activities, compared to around 20 to 30% for Korean adolescents and under 10% for adolescents in Kenya. Digital culture has added another dimension — by 2015, 81% of 13 to 17-year-olds had a social network profile, up from 55% in 2007, and online engagement can serve as a space for exploring identity and self-expression.

Friendships in adolescence change in character as well as in importance. Youniss and Smollar (1985) surveyed 1049 adolescents aged 12 to 19 and found that by 14 to 16 years, friendships were characterised by mutual intimacy — a depth of closeness and self-disclosure that hadn't been present in earlier friendships. Twelve to fourteen-year-olds already rated intimacy and emotional support as more important than younger children did. The takeaway from Youniss and Smollar (1985) is that the need for intimate friendship — what Sullivan called "chumship" — emerges strongly in preadolescence and deepens through the teenage years. Berndt, Hawkins, and Hoyle (1986) compared how early adolescents and younger children interacted with friends versus non-friends, and found that early adolescents competed less and shared more with friends than with non-friends, whereas younger children actually showed the opposite pattern. The takeaway from Berndt, Hawkins, and Hoyle (1986) is that by early adolescence, the special reciprocity of friendship is genuinely distinctive — adolescents treat friends differently from peers in general in ways that younger children don't yet. Rice and Mulkeen (1995) showed that this continues — 17-year-olds report more intimacy between friends than 14-year-olds do. These changes map onto Selman's stages of friendship understanding, with the transition from late childhood to early adolescence representing the shift from "fair-weather cooperation" to "intimate and mutually shared relationships," and mid to late adolescence involving a move towards more autonomous and less exclusive friendships — the intensity of early adolescent friendships settles into something more sustainable.

Adolescents also tend to choose friends who are similar to themselves, particularly in terms of behaviours like substance use. Berndt and Hoyle (1985) found that friendships increased in stability from childhood to early adolescence, but also that adolescents became more reluctant to form new friendships. The takeaway from Berndt and Hoyle (1985) is that while adolescent friendships become more stable and meaningful, there's also a kind of social conservatism — the cost of a friendship breaking down feels higher, so adolescents invest more carefully. On gender differences in friendship, Rice and Mulkeen (1995) found that girls rated themselves as more intimate with their best friends than boys did, and girls spend more time with friends. However, Youniss and Smollar (1985) found that about 45% of boys had levels of intimacy comparable to most girls, and about 30% of boys had genuinely non-intimate friendships — so the picture is more varied than a simple "girls are closer" story. Romantic relationships also begin to emerge in adolescence, typically following a progression from initial interest in the opposite sex, through using romance as a social status enhancer, to a genuine focus on the relationship itself, and finally to concerns about commitment and bonding.

What about the relationship with parents? Despite all the time spent with peers, parents remain deeply important. Shanahan, McHale, Crouter, and Osgood (2007) found that conflict between adolescents and parents peaks at around age 13 and tends to be most frequent in early adolescence and most intense in mid-adolescence. But — and this is important — despite these conflicts, most adolescents report good overall relationships with their parents, and there is no strong evidence for a genuine "generation gap" in values. Typically, adolescents and parents conflict over apparently trivial things like dress or curfews, while actually agreeing on bigger issues like education and values. This suggests that the surface-level conflicts may represent deeper concerns about autonomy and control rather than genuine value differences. Adams and Laursen (2007) found that moderate amounts of conflict can actually be beneficial, but high levels are never good. The psychoanalytic account, associated with Blos (1962), predicted that adolescents would go through a process of disengagement from parents — essentially a second individuation process, similar to the toddler's move from dependent infant to self-reliant child. But Rice and Mulkeen (1995) found that intimacy with parents actually increased from age 13 to 17 years — which directly contradicts the psychoanalytic prediction. Relationships are transformed, not severed. Sebald (1986) found that friends and parents act as two separate reference groups for teenagers — both influencing them in different domains — rather than peers simply replacing parents.

Steinberg and Silverberg (1986) described the process not as separation but as individuation — from age 10 to 14, adolescents show an increasing sense of self-control and self-awareness, a de-idealisation of their parents (recognising them as flawed human beings rather than all-knowing authorities), and a decreased dependency. This is associated with the development of other relationships — interestingly, high autonomy from parents has been linked to high celebrity interest, perhaps as a way of finding new idealised figures. There are different types of autonomy: emotional autonomy (having internal representations of parents as separate people rather than idealised figures), behavioural autonomy (actually making independent decisions), and value autonomy (developing your own moral and ethical framework). Smetana's social domain theory highlights that adolescents and parents often disagree about which domains fall under which kind of authority — parents may see certain things as social-conventional rules they have the right to set, while adolescents see those same things as matters of personal autonomy where they should have control.

Baumrind's parenting styles framework is relevant here too. Research consistently shows that the authoritative style — combining warmth, structure, and genuine support for the adolescent's autonomy — produces the best outcomes. Lamborn, Mounts, Steinberg, and Dornbusch (1991) found that authoritative parenting was associated with healthy adolescent development in terms of psychosocial competence and educational achievement. This style balances structure with freedom, and facilitates intellectual development through reasoning and negotiation rather than just issuing commands. Adolescents raised this way tend to identify more with their parents as well. However, the directionality question is worth noting — it's not always clear whether good parenting produces well-adjusted adolescents or whether well-adjusted adolescents are easier to parent in authoritative ways.

The final section covers identity development, which Erikson (1968) described as the central psychological task of adolescence — the challenge of "identity versus identity diffusion." Adolescence is the time of asking "Who am I?" — experimenting with different roles, values, and relationships in a period Erikson called the "psychological moratorium," where identity is not yet settled and this is actually healthy and productive. If this process goes unresolved, the adolescent might slide into foreclosure (committing to an identity that isn't really self-determined, often just adopting parental values uncritically) or form a negative identity (deliberately taking on the identity that others don't want for them, as a form of rebellion). Marcia (1980) operationalised Erikson's framework into four formal identity statuses. Identity diffusion means the person is avoiding commitment altogether and not even exploring options. Identity foreclosure means they have committed to beliefs but without having explored alternatives — they've adopted an identity, but it wasn't arrived at through genuine self-exploration. Moratorium means they're in an active state of exploration and questioning but haven't yet resolved it. Identity achievement means they've gone through the exploration and come out the other side with a genuine, self-determined commitment. Phillips and Pittman (2007) found that a diffuse-avoidant identity style — the tendency to avoid commitment and exploring identity altogether — was associated with lower self-esteem, lower optimism and self-efficacy, and higher levels of delinquent attitudes and hopelessness. The takeaway from Phillips and Pittman (2007) is that how adolescents engage with the identity formation process has real consequences for their wellbeing, not just their sense of self. Berzonsky proposed an "identity style" approach — looking at identity formation as a process rather than just an outcome — with people being informational (actively seeking and evaluating information about themselves), normative (following the expectations of significant others), or diffuse-avoidant.

The lecture illustrates the shift in self-concept across adolescence beautifully with two examples. A 15-year-old's self-description is full of contradictions and confusion — how can I be cheerful with friends and then come home and be sarcastic with my parents? Which is the real me? An 18-year-old's description shows much more integration — they have a clear sense of the kind of person they want to be, can acknowledge that they don't always live up to their own standards, but have a stable core sense of identity that doesn't depend as heavily on others' opinions. This captures the developmental shift from mid-adolescence (identifying contradictions and finding them confusing) to late adolescence (integrating contradictions into a coherent self). Meilman (1979) showed through a cross-sectional study of 12 to 24-year-old males that identity achievement continues to increase across and beyond adolescence — it's not a single moment of resolution but a gradual process that extends well into adulthood.

It's also worth noting that the concept of an "identity crisis" may itself be culturally biased. In some societies, foreclosure — adopting the identity your community and family have mapped out for you — may be more adaptive than the Western-idealised path of individual self-exploration and achievement. Adolescence is also being prolonged in many societies by extended education, which gives young people more time in the moratorium state. And the statuses don't always follow a neat developmental sequence — people can move between them, and changes can be gradual rather than sudden. The overall message is that establishing a sense of identity is the primary psychological task of adolescence, but it doesn't have to involve crisis, and for most people it leads gradually to a stable, independent sense of self that carries forward into adult life.