On Tuesday, the U.S. Supreme Court invalidated the death penalty for those who committed crimes before they were 18 years old. Juvenile crime may “reflect unfortunate yet transient immaturity,” argues the majority, since adolescents tend to be more reckless and easily influenced than adults. How do experts measure a kid’s level of maturity?
With questionnaires, brain scans, and videogames. Amicus briefs filed with the court from a number of organizations (including the American Psychiatric Association and the American Psychological Association) presented three types of evidence to support the general notion that teenagers are folly-prone. Psychological tests of various types show that kids make decisions differently as they get older; neurological imaging data show that an adolescent brain has not yet reached full maturity; and real world statistics show that children engage in more reckless behavior, on average, than adults.
A typical questionnaire used in research on teenage maturity would ask people of various ages to rate how much they agree with various statements like “I make decisions without thinking about them.” The subject chooses one of five choices: Strongly Agree, Agree, Undecided, Disagree, or Strongly Disagree. By assigning a number of points to each answer, psychologists can tally up a total score for each subject that corresponds to a personality trait, like impulsiveness.
Psychologists can also use games or simulation environments to test impulse control. One game, called the Iowa gambling task, asks teenagers to choose a card from one of four decks, over and over again. Each card has a different value, positive or negative, and each deck has a different mix of cards. Younger kids tend to be less cautious, going for decks from which they’ve received big, one-time rewards, even if the other decks provide better odds overall. In videogames that simulate driving, teens tend to speed up when they see a yellow light, and they crash more often than adults.
Neurological imaging research shows that the frontal lobes of adolescents are less developed, in certain ways, than those of adults. The frontal lobes are thought to be involved with decision-making and planning for the future; indeed, the first use of the Iowa gambling task showed that patients with frontal lobe damage had particular deficiencies in these areas.
Real-world statistics support the laboratory findings, showing that teenagers are more likely to get in car accidents, for example, or have unprotected sex. But how can you figure out the maturity level of a particular kid? When a judge needs this information (usually during sentencing, or when a prosecutor wants to try a juvenile in criminal court), evidence about the defendant’s maturity can be presented in court.
In these cases, judges don’t rely exclusively on the results of questionnaires or videogame assessments (although these are sometimes introduced in expert testimony). Sometimes they hear from character witnesses, like the defendant’s schoolteachers, who will describe if he or she seemed immature or prone to taking risks. And then there are the little things; a smart defense attorney will dress juvenile clients in clothes that make them seem younger, like oversized sweaters instead of suit jackets.
Explainer thanks Laurence Steinberg of Temple University and Marsha Levick of the Juvenile Law Center.
