Potato Chipping

Adolescent Brains and the New Phrenology

Adolescence is popularly considered a biological inevitability largely due to the prevalence of misleading claims about the adolescent brain, such as the following which appeared recently in the New York Times:

While we used to think the brain was relatively mature by 16 or 18, in fact it is still developing into the mid-20s. What does develop early is the pleasure-seeking area, the nucleus accumbens. The regions that help with abstract thinking, decision-making and judgment are still maturing, and therefore less likely to inhibit the pleasure-seeking behavior.

In fact, it’s those who argue that adolescents are intractably limited by underdeveloped brains who are displaying deficient abstract thinking and judgment, for several reasons:

• Behavioral studies do not support the hypothesis that adolescents are biologically or cognitively deficient. Memory peaks shortly after puberty. Raw intelligence scores peak around age 14. Piaget’s formal operational thinking stage is usually attained by age 15. Lawrence Kohlberg found most teens are capable of moral reasoning at the level of adults. And behavioral studies of decision making and judgment have also found that teens perform at a level equal to adults. (Source)
• The causal relationship between brain activity and behavior is unclear. Might behavior produce brain activity? Although there is a definite pattern of brain activity associated with schizophrenia, for example, Joseph Dumit has shown that many schizophrenics actually have “normal” brains. Yet even scientists who (should) know that correlation does not imply causation frequently conclude from correlational studies that brain activity is causing behavior.
• To attach the labels of “developing” or “maturing” to changes in brain activity over time is to impose a narrative not reflected in the data. Suppose the same changes were found to occur between the ages of 40 and 55, rather than ages 10 and 25. No one would think to apply the “maturing” descriptor, because the 40 year old is already “mature.” When the data is interpreted to coincide with cultural expectations of extended adolescence, however, the descriptor is uncritically applied.

Cross-cultural data overwhelmingly demonstrate that adolescence is a social construction. Fifty-five percent of societies studied by anthropologists don’t even have a word for “adolescence.” Contemporary adolescence has its roots not in biology, but in the urbanization, immigration, labor and educational movements, and misguided psychological theories of the nineteenth and early twentieth centuries.

The empirical data generated from new brain scan technologies, then, are used to reinforce hierarchical age relationships much as phrenology was used to reinforce hierarchical class relationships in the nineteenth century. No doubt brain activity is more strongly correlated with psychosocial behavior than skull shapes, but this is not a high bar to clear–glaring disparities remain and at present the causal inferences are just as dubious.

Until these problems are resolved, telling youths they lack the cranial capacity to regulate their behavior is no more scientifically valid than slandering someone for having the brainpan of a stagecoach tilter.