Article summary of Peers increase adolescent risk taking by enhancing activity in the brain’s reward circuitry by Chein et al. - 2011 - Chapter

Introduction

Adolescents behave more at risk than children or adults. This risky behaviour can be characterized as behaviour that can be prevented (for example, binge drinking or traffic accidents due to wild driving). Many professionals state that this behaviour poses the greatest threat to the well-being of adolescents. The risky behaviour that adolescents display differs from the risky behaviour of adults in terms of social background (adolescents often behave more at risk when peers are present) and the quantity. Recent research shows that the risky behaviour of adolescents is directly influenced by the presence of peers: as soon as peers are present, adolescents are more at risk. This has not been found in adults. It appears that two neuronal systems are involved in the tendency toward risky behaviour in adolescents:

• The spur processing system (ventral striatum including the nucleus accumbens and the orbitofrontal cortex).

• The cognitive control system (lateral prefrontal cortex).

Previous research into impulsive and risky behaviour has often observed increased activity in the brain areas involved in incentive processing. In addition, studies found reduced activity in brain structures involved in cognitive control. Both brain systems are subject to many changes during adolescence. The first system undergoes many changes, particularly in the early adolescence period, due to the distribution and density of dopamine receptors. This also explains the greater sensitivity to reward in this period.

The cognitive control system matures more slowly and also takes longer to do so. This is partly due to the reduction of grey matter and the increase of myelin layers. This process starts before the onset of adolescence and lasts until at least the 25th year of life. Due to maturation, adolescents are becoming better at positions related to executive functioning and flexibility.

It seems that the risky behaviour of adolescents is caused by an imbalance between the maturation of the aforementioned systems. In the current study, adolescents, young adults and adults measured brain activity when making decisions in a simulated traffic light task. The ultimate goal of this game is to achieve the highest possible financial reward in the shortest possible time. Every participant played the game with and without peers looking at them.

Methods

Attendees

40 people participated in this study: 14 adolescents between 14-18 years (including 6 women), 14 young adults between 19-22 years (including 7 women) and 12 adults between 24-29 years (including 6 women).

Procedure

The traffic light task is a driving task where the participant must keep control of the vehicle from the driver's position. Each participant did the game four times (twice with, and twice without spectators). Each round had twenty intersections (so there were twenty trials per round) and lasted less than six minutes. By pressing a button, the participant could indicate whether or not to stop at the intersection, while the traffic light went from green to orange to red. By varying the timing of the traffic lights and the chance of a collision when driving through red, the game remained unpredictable. Risky behaviour was rewarded financially (by a higher amount if the participant was faster). Waiting for green light resulted in less time due to the time delay. However, when the risky behaviour caused a collision, the loss of time was greater (and the financial reward smaller) than if the participant waited for the green light.

Each participant had to bring two friends of the same gender and in the same age group. In the spectator condition, the participant was told that his or her friends were watching in an adjacent room. This entailed a surprise effect since the participants were not informed of this in advance. During the break for the spectator condition and between the two spectator rounds, the participant and the spectators were able to speak to each other via the intercom. The peers were instructed about what they were allowed to say and what they were not allowed to say to prevent behavioural influences.

After the traffic light task (where the participant was in an MRI scanner), the participants were asked to complete questionnaires. These questionnaires investigated the degree of impulsiveness, sensation seeking and sensitivity to the influence of peers.

Results

Behavioural

Adolescents and (young) adults showed similar behaviour in the condition without spectators. However, this was not the case in the condition with spectators. The participants in the adolescent group were the only ones who took more risk when their friends watched. They drove more often through red and also had an accident more often.

Regression analysis showed that behaviour was significantly related to the degree of sensation seeking. There was no significant relationship between behaviour and impulsivity. Task performance is therefore mainly influenced by the extent to which someone seeks to reward and sensation.

fMRI

In the current study, particular attention was paid to those areas of the brain, which left the main effect of age or an interaction effect of age and condition.

In areas in the left prefrontal cortex, there was more brain activity in adults than in adolescents.

The influence of peers on adolescents was evident in increased activation in the ventral striatum and the orbitofrontal cortex. This indicates that the presence of peers makes the incentive processing more sensitive. These results were not found in (young) adults.

In addition, different regions of interests (ROIs) were looked at to make the decision-making process dependent on the riskiness of the given situation. In adolescents, there was more activation in the ventral striatum and the orbitofrontal cortex, related to risky decisions. This was not found with the (young) adults.

The self-report of sensitivity to peers turned out to be significantly related to the activation patterns in the ventral striatum. This applied to all age groups. 

Discussion

The results from the current study replicate earlier research findings. The unique way of measuring the influence of peers in the current study contributes to a better understanding of the effect of peers' influence on the decision-making process during adolescence. The riskier behaviour when peers looked at it cannot be explained by the encouragement of these peers, as there was no contact during the task and the contact between the tasks was subject to strict rules. An explanation that may be possible is a neural sensitivity due to the incomplete maturation of the brain.

The difference in risky behaviour between adolescents and (young) adults in the current study can only be attributed to the presence of peers since all three groups showed similar behaviour in the condition where no spectators were present. In adults, the presence of peers does not even seem to be rewarding at all. In addition, they appear to be better able to use the left prefrontal cortex to inhibit the reward system to make strategic decisions. Regardless of the presence of peers, there was more activation in the aforementioned brain area in adults than in adolescents.

The social influence on decisions made by adolescents can be seen as an interaction between social information processing and the processing of reward.

Adolescents have increased activation in the brain areas involved in incentive processing in response to social stimuli such as face recognition, compared to children and adults. Because of the rewarding effects of the presence of peers, this can lead to a reinforcing stimulus towards the incentive processing system, whereby risky behaviour is experienced as extra rewarding.

It cannot be claimed with certainty that the increased activation in the ventral striatum in adolescents in the current study is purely due to the presence of peers. An alternative explanation can be given, for example, by talking about social uncertainty or greater sensitivity to distraction. These explanations are less likely since other brain regions should also show different activation patterns during the current study.