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The often-repeated myth of brain development ending at the ages of 18 or 25, started circulating in the early 10s, but has never been backed up by observable trends in brain imaging evidence going beyond that age. The perceived incompetence of the modern minor is exaggerated, culture-bound, and can be blamed in part on the highly lucrative "troubled teen" industry and the advocacy science surrounding it.

A little background

This myth reached the status of folklore after a 2005 US Supreme Court decision preventing teenage offenders being executed. In their brief, the American Psychological Association successfully, but fallaciously argued that the teen temperament is uniquely malleable and subject to change. The amicus cites behavioral studies and observations that lack experimental control, otherwise identifying trends that are culture-bound or contradicted by other studies cited by Robert Epstein (for example) in this article. Well known data surrounding the high recidivism and reoffending rates of youth offenders also contradicts the "unique plasticity" or "second chance" narrative (sources in linked article). So like many MAP-adjacent topics, the source of the myth is a classical case of "bad science following good (or at least political) intentions". Since this Supreme Court decision, some less reputable brain scientists have cottoned on to the trend, sometimes making spurious claims that contradict their own experimental findings - one supposes, in an attempt to curry favor.

Generalizations are often made from physiological data to competences, and then a further leap of faith is made to "policy implications". This common fallacy of relevance is the hallmark of advocacy science; even inspiring one legal scholar to coin the term "Brain Overclaim Syndrome". Debate Guide: Teen brain, gives some rebuttals. Use in combination with the following sources:

Basic Physiology/volumes

Total brain volume and Gray Matter volume appears to reach a peak before or during puberty, declining thereafter. White matter, which has a less critical function in cognition, takes until the mid-40s to peak in volume. Neither of these represent any milestone other than the start of puberty. It is clear that some parts of the brain develop into and beyond early adulthood, while others might regress somewhat. This is a normal process of aging, since brain development and cognitive capacity is highly elastic and dependent on ones environment.

• Giedd, J. et al (1999). "Brain development during childhood and adolescence: a longitudinal MRI study," Nature Neuroscience, 2(10):861-3.

  "Pediatric neuroimaging studies, up to now exclusively cross sectional, identify linear decreases in cortical gray matter and increases in white matter across ages 4 to 20. In this large-scale longitudinal pediatric neuroimaging study, we confirmed linear increases in white matter, but demonstrated nonlinear changes in cortical gray matter, with a preadolescent increase followed by a postadolescent decrease. These changes in cortical gray matter were regionally specific, with developmental curves for the frontal and parietal lobe peaking at about age 12 and for the temporal lobe at about age 16, whereas cortical gray matter continued to increase in the occipital lobe through age 20. The subjects for this study were healthy boys and girls participating in an ongoing longitudinal pediatric brain-MRI project at the Child Psychiatry Branch at the National Institute of Mental Health. [...] This MRI study demonstrates a preadolescent increase in cortical gray matter; this phenomenon was previously obscured, probably by the lack of longitudinal data, as even in an analysis of the 145 cross-section-al data points in our sample, the largest to date, we could not detect nonlinearity in these developmental curves".

• Bartzokis, G. et al., (2001). "Age-related changes in frontal and temporal lobe volumes in men: a magnetic resonance imaging study," Arch Gen Psychiatry, Aug; 58(8):774.

  "Methods: Seventy healthy adult men aged 19 to 76 years underwent magnetic resonance imaging. Coronal images focused on the frontal and temporal lobes were acquired using pulse sequences that maximized gray vs white matter contrast. The volumes of total frontal and temporal lobes as well as the gray and white matter subcomponents were evaluated. Results: Age-related linear loss in gray matter volume in both frontal (r = -0.62, P<.001) and temporal (r = -0.48, P<.001) lobes was confirmed. However, the quadratic function best represented the relationship between age and white matter volume in the frontal (P<.001) and temporal (P<.001) lobes. Secondary analyses indicated that white matter volume increased until age 44 years for the frontal lobes and age 47 years for the temporal lobes and then declined. Conclusions: The changes in white matter suggest that the adult brain is in a constant state of change roughly defined as periods of maturation continuing into the fifth decade of life followed by degeneration. Pathological states that interfere with such maturational processes could result in neurodevelopmental arrests in adulthood."

• Del Giudice, M, (2014). "Middle Childhood: An Evolutionary-Developmental Synthesis", Child Development Perspectives, Volume 8, Number 4, Pages 193–200.

  Del Giudice has age 6-8 as the peak for gray matter (see tables).

  "By age 6, the brain has almost reached its maximum size and receives a decreasing share of the body’s glucose after the consumption peak of early childhood (see Figure 1; Giedd & Rapoport, 2010; Kuzawa et al., in press). However, brain development proceeds at a sustained pace, with intensive synaptogenesis in cortical areas (gray matter) and rapid maturation of axonal connections (white matter; Lebel, Walker, Leemans, Phillips, & Beaulieu, 2008). The transition to middle childhood is marked by a simultaneous increase in perceptual abilities (including a transition from local to global visual processing), motor control (including the emergence of adult-like walking), and complex reasoning skills (Bjorklund, 2011; Poirel et al., 2011; Weisner, 1996). The most dramatic changes probably occur in the domain of self-regulation and executive functions: Children become much more capable of inhibiting unwanted behavior, maintaining sustained attention, making and following plans, and so forth (Best, Miller, & Jones, 2009; Weisner, 1996)."

Competence

• Epstein, Robert (2010). "Adultness," Teen 2.0, 148-157.

  "After reviewing the relevant scientific literature, interviewing many adults, and consulting with three other psychologists and two psychiatrists with expertise in adult development issues, we concluded that there are fourteen different skill-sets or "competencies" [love, sex, leadership, problem solving, physical abilities, verbal and math, interpersonal skills, responsibility, managing high-risk behaviors, work, education, personal care, self-management, and citizenship] that distinguish adults from non-adults. [...] For three of the competencies--love, leadership and problem solving--we did find statistically significant differences between the mean scores of teens and adults, with adults outscoring the teens. But the absolute differences were small. [...] On two other scales--work and self-management--the differences between the adult scores and teen scores were marginally significant (at the .05 level), again in the adults' favor, but the absolute differences were less than 4 percent. On the other nine scales, we found no significant differences at all between the adult and teen scores. [...] fifty five of the adults in our sample were college graduates--more than double the rate of college graduates in the United States."

• Epstein, Robert (2007). "The Myth of the Teen Brain," Scientific American Mind, April/May, 57-63.

  "Visual acuity, for example, peaks around the time of puberty. "Incidental memory"—the kind of memory that occurs automatically, without any mnemonic effort, peaks at about age 12 and declines through life. [...] In the 1940s pioneering intelligence researchers J. C. Raven and David Wechsler, relying on radically different kinds of intelligence tests, each showed that raw scores on intelligence tests peak between ages 13 and 15 and decline after that throughout life. Although verbal expertise and some forms of judgment can remain strong throughout life, the extraordinary cognitive abilities of teens, and especially their ability to learn new things rapidly, is beyond question. And whereas brain size is not necessarily a good indication of processing ability, it is notable that recent scanning data collected by Eric Courchesne and his colleagues at the University of California, San Diego, show that brain volume peaks at about age 14."

• Moshman, David (2011). "Adolescent Rationality and Development: Cognition, Morality, and Identity, Third Edition.

(Intro) "Adolescents are qualitatively and categorically distinct from children. There is no empirical support, however, for a state of rationality or maturity common to most adults, rately seen in adolescents. Even young adolescents often show forms and levels of rationality beyond the competence of many adults, and adults of all ages often fall short of rational standards met by many adolescents [...] it is not surprising to find that in most societies for most of human history there was no such thing as adolescence, at least as we understand it (Epstein, 2007; Grotevant, 1998; Hine, 1999)."

"Postchildhood developmental changes in thinking are not tied to age and do not culminate in a state of maturity. Although it seems likely that many individuals show progress beyond childhood in the quality of their problem solving, decision making, judgment, and planning (Cauffman & Woolard, 2005; Steinberg & Scott, 2003), the deployment and progress of thinking in adolescence and beyond is highly variable, depending on specific interests, activities, and circumstances (Fischer, Stein, & Heikkinen, 2009). No theorist or researcher has ever identified a form or level of thinking routine among adults that is rarely seen in adolescents. Adolescent thinking often develops but not through a fixed sequence and not toward a universal state of maturity [...] It seems almost irresistible for adults to see themselves as having achieved a state of maturity that adolescents (and even younger adults) have not yet reached, but brain research provides no evidence to support the postulation of advanced states of maturity attained by the most or all adults but few adolescents. Many people continue to develop long beyond childhood, and their brains reflect those changes, but beyond age 12, there is no natural and universal state of maturity waiting to be achieved."

"Developmental changes beyond age 12 to 14 are much too stable and individualized, it appears to me, for a developmental panel, even if it included brain experts, to succeed in distinguishing age groups on the basis of their age development. Second, there is the reductionist fallacy. Brain data seem more scientific than behavioral data, but they are not, nor do they provide us with ultimate explanations, even if psychology can in principle be reduced to biology, a dubious proposition, we are a very long way from achieving such a reduction."

• Waber, D.P., et al. (2007). "The NIH MRI Study of Normal Brain Development: Performance of a Population Based Sample of Healthy Children Aged 6 to 18 Years on a Neuropsychological Battery," Journal of the International Neuropsychological Society, 13(5), 729-746.

  "Perhaps most intriguing are the age-related trajectories for raw score performance. For most tasks, proficiency improved dramatically between 6 and 10 years of age, leveling off during early adolescence (approximately 10 to 12 years of age), suggesting that for many neurocognitive tasks, children approach adult levels of performance at that age. For a few measures, scores increased linearly throughout the age range. These were tasks that assessed basic information processing, such as Coding, Digit Span, and Spatial Span. Still others were associated with a non-linear component during adolescence. Some showed a flattening of the curve followed by another period of acceleration, suggesting another spurt in mid-adolescence. Verbal learning actually reversed direction with performance declining in later adolescence."

• Adler, N.E., & Matthews, K. (1994). "Why do some people get sick and some stay well?," Annual Review of Psychology, 45, 229-259.

  "However, empirical tests show that adolescents are no less rational than adults. Applications of rational models to adolescent decision-making show that adolescents are consistent in their reasoning and behavior after the salient set of beliefs is assessed (Adler et al 1990). Quadrel et al (1993) demonstrated that adolescents are no more biased in their estimates of vulnerability to adverse health outcomes than are their parents."

• Weithorn, L. A. & Campbell, S. B. (1982). "The competency of children and adolescents to make informed treatment decisions," Child Development, 53(6), 1589-1598.

  "In general, minors aged fourteen were found to demonstrate a level of competence equivalent to that of adults. [...] The ages of eighteen or twenty-one as the "cutoffs" below which individuals are presumed to be incompetent to make determinations about their own welfare do not reflect the psychological capabilities of most adolescents."

• Offer, D. (1987). "In defense of adolescents," Journal of the American Medical Association, 257, 3407-3408.

  Mike Males describes this study: "Northwestern University psychiatrist Daniel Offer, the nation’s leading researcher on adolescents, studied 30,000 teenagers and adults from the 1960s to the 1990s. He and his colleagues found 85% to 90% of teens held attitudes and risk perceptions similar to that of their parents, were not alienated, did think about the future, were coping well with their lives, and did not display psychological disturbances. "Decision making for adults is no different than decision making among teenagers,” Offer reported in 1987 in the Journal of the American Medical Association."

• Offer, D., and Schonert Reichl, K.A. (1992). "Debunking the myths of adolescence: Findings from recent research," Journal of the American Academy of Child & Adolescent Psychiatry, 31, 1003 1014.

  "[T]he effects of pubertal hormones are neither potent nor pervasive (Brooks-Gunn and Reiter, 1990). [...] Adolescence does not occur in a vacuum and is significantly affected by the sociocultural context in which it occurs. A recent investigation by Enright et al. (1987) illustrates this point. This study was based on the careful reading of 89 articles in the Journal of Genetic Psychology for the past 100 years. The articles were rated for their conceptions about the nature of adolescence. Enright et al. demonstrated ideological bias in approaches to understanding adolescent psychology, specifically in relation to economic conditions. Specifically, in times of economic depression, theories emerged in the literature that portrayed adolescents as "immature, psychologically unstable, and in need of prolonged participation in the education system" (p. 553). In contrast, during wartime, the psychological competence of adolescents was accentuated. The authors point out, "The field of adolescent psychology is not free from the societal influences that impinge upon legislators, educators, and parents in shaping American adolescents" (p. 554)."

• Quadrel, M. J., Fischhoff, B., & Davis, W. (1993). "Adolescent (in)vulnerability," American Psychologist, 48, 102-116.

  "Three groups of subjects were asked to judge the probability that they and several target others (a friend, an acquaintance, a parent, a child) would experience various risks. Subjects were middle-class adults, their teenage children, and high-risk adolescents from treatment homes. All three groups saw themselves as facing somewhat less risk than the target others. However, this perception of relative invulnerability was no more pronounced for adolescents than for adults. Indeed, the parents were viewed as less vulnerable than their teenage children by both the adults and those teens. These results are consistent with others showing small differences in the cognitive decision-making processes of adolescents and adults. Underestimating teens' competence can mean misdiagnosing the sources of their risk behaviors, denying them deserved freedoms, and failing to provide needed assistance."

Informed consent

Children's decision-making ability has recently come under scrutiny, with consent to clinical research, gender transition and vaccination efforts the most common contemporary themes so far. In a paper that repeated some of the myths re. development of older teens, it was nevertheless held that for children over the age of 11.2 need not be assessed individually for their ability to give consent to take part in clinical research.

• Hein, M. et al, (2015). "Informed consent instead of assent is appropriate in children from the age of twelve," BMC Medical Ethics, 2015, 16:76.

  "Children between 9.6 and 11.2 years were in the change-over period, an individual assessment of competence might be applicable in this age group. Children of 11.2 years and above can generally be considered decision-making competent, and although they need a supportive context, no individual assessment is needed."

Risk Taking/Impulsivity/Prefrontal Physiology

The oft-repeated myth of the human brain maturing fully at 25, is simplistic and outdated. If impulse control were dependent upon prefrontal volume, we would see no such thing as the quiet, studious preschooler - as all preschoolers have a tiny prefrontal cortex. As the previous studies suggest, the brains of teenagers are already losing gray matter and raw processing power is already declining by that age. Further studies are now informing us that functions of the prefrontal cortex are borrowed from other parts of the brain in teens, and raw levels of impulse-control are equal to or greater than that of adults. However, teenage boys in particular, might be slightly less discriminatory when facing tasks within a positive or negative emotional context. While this might manifest in poorer performance within an experimental context, it is likely to be an adaptive (possibly pro-reproductive) trait that is net beneficial to socialization/competence building during youth. Further, there is no sound evidence to support the idea that the amygdala is the brain's "fear center" - so any differences in teens' amygdala response can not be traced to function, let alone be ascribed to a mental deficiency. One would also have to account for the fact that when compared to teens, smaller children generally show similar levels of amygdala activation to adults.

• Steinberg, L., (2008). "A Social Neuroscience Perspective on Adolescent Risk-Taking," Developmental Review, Volume 28, Issue 1, March 2008, Pages 78-106.

  "Among the widely-held beliefs about adolescent risk-taking that have not been supported empirically are (a) that adolescents are irrational or deficient in their information processing, or that they reason about risk in fundamentally different ways than adults; (b) that adolescents do not perceive risks where adults do, or are more likely to believe that they are invulnerable; and (c) that adolescents are less risk-averse than adults. None of these assertions is correct: The logical reasoning and basic information-processing abilities of 16-year-olds are comparable to those of adults; adolescents are no worse than adults at perceiving risk or estimating their vulnerability to it (and, like adults, overestimate the dangerousness associated with various risky behaviors); and increasing the salience of the risks associated with making a poor or potentially dangerous decision has comparable effects on adolescents and adults (Millstein & Halpern-Felsher, 2002; Reyna & Farley, 2006; Steinberg & Cauffman, 1996; see also Rivers, Reyna, & Mills, 2008, this issue). Indeed, most studies find few, if any, age differences in individuals’ evaluations of the risks inherent in a wide range of dangerous behaviors (e.g., driving while drunk, having unprotected sex), in their judgments about the seriousness of the consequences that might result from risky behavior, or in the ways that they evaluate the relative costs and benefits of these activities (Beyth-Marom, Austin, Fischoff, Palmgren, & Jacobs-Quadrel, 1993). In sum, adolescents’ greater involvement than adults in risk-taking does not stem from ignorance, irrationality, delusions of invulnerability, or faulty calculations (Reyna & Farley, 2006)."

• Casey, B., (2013). "The Teenage Brain: Self Control," Current Directions in Psychological Science, Volume: 22 issue: 2, page(s): 82-87.

  "Adolescence, by definition, involves new demands on the individual as she or he moves from dependence on the family unit to relative independence. This developmental period is not specific to humans, as evidenced by the increases in novelty seeking, interactions with peers, and fighting with parents observed in other species (see Romeo, 2013; Spear, 2013; both in this issue). These behaviors are thought to have evolved to serve adaptive functions related to successful mating and obtainment of resources necessary for survival (Spear & Varlinskaya, 2010). [...] To suggest that this period of development is one of no brakes or steering wheel (Bell & McBride, 2010) is to greatly oversimplify it. [...] Self-control—in this case, suppressing a compelling action—showed a different developmental pattern in the context of emotional information than in its absence, especially for males (Tottenham, Hare, & Casey, 2011). As illustrated in Figure 1 (also see Fig. 1 in Hare et al., 2008; National Research Council, 2011), when no emotional information is present, not only do many adolescents perform as well as adults, some perform even better. However, when decisions are required in the heat of the moment (i.e., in the presence of emotional cues; Fig. 2a), performance falters (Fig. 2b). Specifically, adolescents have difficulty suppressing a response to appetitive social cues relative to neutral ones. [...] Recently, a number of human imaging studies have attempted to evaluate this model and test for unique patterns of brain activity in adolescents during stereotypical risky behavior in the context of incentives (Chein, Albert, O’Brien, Uckert, & Steinberg, 2011; J. R. Cohen et al., 2010; Geier, Terwilliger, Teslovich, Velanova, & Luna, 2010; Van Leijenhorst et al., 2010). This work has challenged the view that diminished self-control in adolescents is due to a less mature prefrontal cortex that leads to less successful exertion of regulatory control on behavior (Bell & McBride, 2010). [...] Indeed, if the objective of adolescence is to gain independence from the family unit, then providing opportunities for adolescents to engage in new responsibilities is essential. Without opportunities and experiences to help optimally shape the adolescent’s brain and behavior, the objectives of this developmental phase will not easily be met."

• Bronski, J. (2021). "An Empirical Introduction to Youth"

  "The 2010 study looked at, among many, a white matter tract called the “uncinate fasciculus [which] … is a large fiber track connecting three key regions involved in emotion regulation: [the] amygdala, lateral and medial prefrontal cortex”136. This connection, which considering the evidence is safely considered to be done with all meaningful structural development by the end of puberty (which is likely to be before the age of fifteen), is exactly what some scientists claim causes a functional difference in teens. Specifically, they claim, among other things, that in teens the amygdala struggles to communicate with the frontal lobe, leading to lower inhibition of primal amygdalic functions. There is no evidence for this claim, since we have seen that the uncinated fasciculus, the main track connecting the amygdala and the frontal lobe, is mature at the end of puberty. So far we have seen that gray matter, in the prefrontal cortex and the rest of the brain, is accumulated until puberty, when it begins to be pruned. This pruning will continue into old age; there is nothing significant about the age of 25 when it comes to loss of gray matter. We have also seen that the accumulation of white matter reaches its peak rate at the age of one year, and continues at decreasing rates until the age of approximately 45, in the prefrontal cortex and elsewhere in the brain. There is nothing significant about the age of 25 when it comes to the accumulation of white matter. Finally, in direct contrast to the unscientific claim that “Adults think with the prefrontal cortex, the brain’s rational part … Teens process information with the amygdala,” teens do in fact have working prefrontal cortexes, and the connections between that part of the brain and the amygdala are mature by the end of puberty. There is nothing significant about the age of 25 when it comes to the connection between the hindbrain and the forebrain, or the extent to which one “thinks” with either part of the brain. How do we now judge the statement that “The rational part of a teen’s brain isn’t fully developed and won’t be until age 25 or so?” Poorly. The proposition is clearly unsupported by the data regarding structural changes in the brain. Based on what we have reviewed, the claim seems totally arbitrary. Let us be charitable and look for other evidence that (Landouceur et al. 2012) might comment on this view. Perhaps the function of the brain only reaches mature levels at the age of 25. Development of Organ Function Function is what matters. For whatever reason, teen-brain neuroscientists love to obscure the debate on the maturity of the “teen brain” by making claims about its supposed structural immaturities. As we have seen, the actual evidence for these immaturities is sparse at best. Many claims of structural and functional immaturity rest on young, physically immature participants, which are grouped with older teens. Claims are then extended to all teenagers and hyperbolized in the news cycle. For instance, Dr. Giedd, who co-authored the 2004 gray matter study, has gone on the news and made claims about the immaturity of the brain “through adolescence.” The definition of adolescence is, of course, slippery. His data shows structural maturity by the age of 14 or 15, which he vaguely refers to as “late adolescence.” The WHO then defines adolescence as occurring during the ages 10-19. Many in the news refer to the age of 25 as the specific age at which the brain reaches maturity. How this came about has already been hinted at: earlier, a source was reviewed which showed that myelination of the frontal lobes continues until the mid-forties. One scientist, BJ Casey, ran an experiment which only featured participants up to the age of 24-25, and found that myelination continued to the highest age featured in the study. Out of this came the claim that the brain is still developing until the age of 25. In reality, further data shows that by this metric, the brain develops until 45! Dr. Frances Jensen wrote a whole book on this misleading claim, saying in a promotion article published in Time, The myelination process starts from the back of the brain and works its way to the front. That means the prefrontal cortex, the area of the brain involved in decisionmaking, planning and self-control, is the last part to mature. It’s not that teens don’t have frontal- lobe capabilities but rather that their signals are not getting to the back of the brain fast enough to regulate their emotions. It’s why risk-taking and impulsive behavior are more common among teens and young adults. “This is why peer pressure rules at this time of life,” says Jensen. “It’s why my teenage boys would come home without their textbook and realize at 8 p.m. that they have a test the next day. They don’t have the fully developed capacity to think ahead at this time.” She also claims in her book that the teenage brain is “only 80% developed,” without a source."

• Romer, D. (2010). "Adolescent Risk Taking, Impulsivity, and Brain Development: Implications for Prevention," Developmental Psychobiology, 52(3): 263–276.

  "A review of the evidence for the hypothesis that limitations in brain development during adolescence restrict the ability to control impulsivity suggests that any such limitations are subtle at best. Instead, it is argued that lack of experience with novel adult behavior poses a much greater risk to adolescents than structural deficits in brain maturation [...] The evidence we have reviewed suggests that adolescent risk taking is not a universal phenomenon and that individual differences related to at least three types of impulsivity underlie such behavior in adolescents. Furthermore, at least two forms of impulsivity are associated with weak executive function as assessed by working memory and response inhibition tasks. However, sensation seeking does not appear to be inversely related to either of these executive functions and may actually be somewhat positively related to working memory ability."

• Romer, D. et al, (2017). "Beyond stereotypes of adolescent risk taking: Placing the adolescent brain in developmental context," Developmental Cognitive Neuroscience, Volume 27, Pages 19-34.

  "In conclusion, we have presented an alternative model of adolescent brain development that emphasizes the accumulation of experience as adolescents age and transition to adulthood, with concomitant changes in judgment and decision making (see Table 1 for a summary of differences between the Life-span Wisdom Model and Imbalance Models). The model explains much of the apparent increase in adolescent risk taking as an adaptive need to gain the experience required to assume adult roles and behaviors. The risk-taking that reflects lack of control or excessive sensitivity to immediate rewards is primarily an individual difference that characterizes some persons from an early age that can persist well into adulthood. At the same time, the adolescent brain is supremely sensitive to the learning that can occur during this period and has cognitive capacities to take advantage of the experience gained. The result is a brain with integrated circuits encompassing executive function (i.e., cognitive control and inhibition), as well as verbatim and gist memory networks, which can be called upon to negotiate both novel and familiar situations. The preservation of robust gist thinking maintains wise decision making during later adulthood when cognitive control capacities diminish. We believe this approach is more aligned with the scientific evidence, including results that challenge stereotypes about the adolescent brain."

• Moshman, David (2011). "Adolescent Rationality and Development: Cognition, Morality, and Identity, Third Edition.

  "There is no evidence that adolescents are uniquely egocentric or even much different from adults in this regard; on the contrary, research has shown age differences to be minimal or nonexistent (Millstein & Halpern-Felsher, 2002; Quadrel et al., 1993; Smetana & Villalobos, 2009). As fo the specific assertion that adolescents see themselves as invulnerable, it appears instead that adolescents routinely, and often drastically, overestimate their actual vulnerability (Millstein & Halpern-Felsher, 2002). [...] risk taking is not always bad, and adolescents are not uniquely prone to it. People of all ages take risks of all sorts, including foolish and dangerous risks; there is no empirical basis for the common assumption that risk taking is a special phenomenon of adolescence. On the contrary, direct comparisons of adolescents and adults show minimal age differences (Beyth-Marom et al., 1993). Sociological data indicate that when covariates such as poverty are controlled, adolescents are no more prone to risk taking than adults, who in fact take plenty of dubious risks (Males, 2009, 2010)."

Moral reasoning

• Haidt, J. (2001). "The emotional dog and its rational tail: A social intuitionist approach to moral judgment," Psychological Review, 108, 814-834.

  "Turiel (1983) has shown that young children do not believe [that actions are wrong just because they are punished]. They say that harmful acts, such as hitting and pulling hair, are wrong whether they are punished or not. They even say that such acts would be wrong if adults ordered them to be done."

Excerpt Graphic Library

The EGL on Competences and Development has some relevant information. Just right click/save and reproduce by uploading in short-form media to bypass character limits.

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  Basic brain aging primer
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  Teen Brain research summary
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  Age chauvinism
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  BJ Casey
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  Joseph Bronski
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  Full Brain Size and adult-like competences in early childhood
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  Development of reasoning ability in early childhood (Moshman, 2005)
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  Early development of brain - Del Giudice
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  White and Gray Matter levels - Del Giudice (2017)
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  Bethlehem et al, 2022, brain volumes and matter levels by age
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  Giedd 1999 brain matter curves by age
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  Mills et al: Adolescent brains indistinguishable from adult. Variance in gray matter between individuals is far greater than any changes over time.
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  John Raven - Intelligence hits a peak in the mid teens, then plateaus and declines (the decline may have been at least in part due to poorer education in the interwar period).
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  John Raven - Intelligence hits a peak in the mid teens, then plateaus (note improvement in scores obtained in the 1970s)
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  Moshman on common fallacies of teen brain development
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  Moshman continued
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  Moshman continued
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  Laurence Steinberg (2008)
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  Epstein reviewed, plus other references - raw intelligence peak 13-15 y/o
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  2020 meta-analysis on the age of Thelarche (breast budding in girls - start of puberty). Similar for first period.
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  Conclusions of the aforementioned 2020 meta-analysis
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  Physical development - Tanner stages reached considerably earlier than commonly supposed
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  Physical development - Ages of pubertal development lower than commonly stated
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  Girls developing sexual features almost completely by 11