Psychological and neurobiological research shows that adolescents often lack the capabilities to make mature judgments, control impulses, weigh the consequences of their actions and resist coercive pressure when they are with other teens, argued psychologist Laurence Steinberg, PhD, during the Rocky Mountain Psychological Association Conference, April 14-17 in Phoenix.

Steinberg--the Laura H. Carnell Professor of Psychology at Temple University and one of APA's 2005 Distinguished Scientist Lecturers--presented research on the delayed development of adolescents' decision-making capabilities and contended that the court system and lawmakers should weigh adolescents' cognitive and psychosocial development when judging juvenile crimes.

While adolescents usually can distinguish between "right" and "wrong" in a way similar to adults, they might be less able to control their aggressive impulses when provoked, stay level-headed when stressed or think through the consequences of their actions when coerced by others, Steinberg said.

In fact, National Institute of Mental Health studies using functional magnetic resonance imaging have shown that the average brain continues to develop into the mid 20s--particularly in areas of the frontal lobe, the region of the brain most important for planning, reasoning and impulse control.

Coupled with that, adolescents' decisions might be heavily influenced by their peers. For example, in a study in press at Developmental Psychology, Steinberg--in collaboration with graduate student Margo Gardner--tested how often adolescents participated in risky behaviors while driving a car simulator--both with and without their peers present. Indeed, when their friends were with them, the adolescent participants took more chances with their driving than adult participants, such as continuing to drive after a traffic signal had turned yellow, risking the chance of crashing the car. However, when playing the driving game alone, adults and adolescents took risks equally, he said.

These differences are important to note, he said, since juveniles usually commit crimes in groups, whereas adults tend to commit crimes by themselves.

The March U.S. Supreme Court ruling in Roper v. Simmons--which declared the death penalty unconstitutional for juveniles--was a major victory in getting the message out on such adolescent development issues, Steinberg said. In a 5-4 decision, the Supreme Court ruled that 17-year-old Christopher Simmons, who committed first-degree murder in 1994, could not receive the death penalty for his crime (see page 84). Steinberg helped APA draft an amicus curiae brief for the case, which cited his and others' psychological research on adolescent development and supported banning the juvenile death penalty.

"If someone is not able to control impulses, plan ahead or think through the future consequences of his or her actions because of developmental immaturity, he should not be held to the same standards of criminal [conduct] as someone who has that ability," Steinberg said.