Impulsivity for short-term reward in adolescence
Importantly, over late childhood and adolescence, there seems to be a lack of synchrony in the development of two of the critical brain systems that enable fully adaptive behavior.
The ‘rational’ cognitive system, which allows for understanding a problem and arriving at a solution, appears to be well formed at age 16. This seems in step with the maturation of frontal cortex, and on testing a child may give appropriate, adult-like, answers.
However, the system for effective use of information in context – balancing
long term consequences with immediate social and emotional concerns – does not develop in synchrony with such rationality , and so there is a ‘gap’ between the
Studies show that adolescents and young adults become poorer at
responding on problem solving tasks when the complexity of emotion is added . Such tasks would likely involve the interaction of functions across a range of brain areas (including limbic, thalamoamygdala pathway and both left and right frontal systems) .
Furthermore, this ‘gap’ between reason and emotion is exacerbated by an underlying susceptibility for responding to immediate rewards that emerges early in adolescence.
In the ‘teenage brain’ there is a surge of an infusion of reward-oriented neuro-transmitters (dopaminergic activity) and an associated increase in reward-seeking behavior.
It appears, therefore, that the brain system related to rewards (the meso-limbic area) is developing rapidly relative to the other systems. Especially, it seems, compared to the
frontal system that is supposed to regulate it, and the social and emotional systems that will, in time, moderate it.
Changes in brain systems configuration – as connectivity improves with increased
myelination and ongoing cortical pruning – has been shown in longterm neuro-imaging research. This work shows that the areas responsible for high level thinking
such as control of impulses and making judgments about the longer term (the dorso-lateral- prefrontal cortex) only reach adult levels of ‘cortical thickness’ in the late
teenage years .
The teenage brain, therefore, has an adult-like ability to reason, but with a
heightened need for basic reward, and a lowered capacity to buffer immediate influences and potential short-term rewards for greater, longer-term gains – especially in contexts involving peers. This sets the scene for risky decision-making.
As one commentator described, biologically speaking it’s like ‘starting the engines without a skilled driver behind the wheel’.