Adolescents show increased attention and neural activation in response to peer acceptance. Feelings of relatedness with others and perceived acceptance during adolescence are associated with higher self-esteem (1), better adjustment in school (2) and greater self-worth (3). Peer rejection in adolescence is associated with school withdrawal (1), aggression (2) and mental health problems (3).

Social contexts are more salient to adolescents. This can lead to different decision-making abilities around peers (e.g. presence of peers increases risky decision making). Adolescents who feel rejected are more likely to engage in risky behaviour to fit in with the group.

Feedback from peers may reinforce behaviour. This may be due to overlapping neural circuitry for evaluating social and non-social rewards. The ventral striatum supports learning from varying amounts of positive social feedback from peers. The most reinforcing peers had a greater influence on social preferences. Choice behaviour (1), neural activity in the ventral striatum (2) and reaction times (3) may be hypersensitive to rewarding stimuli in adolescence. However, it is also possible that the functional connectivity changes and how neural activity guides expectations and behaviours rather than differences in reward-related learning signals.

Participants liked peers that gave them continuous positive social feedback more than those who rarely gave them positive social feedback. Participants liked peers who gave them frequent feedback more than those who rarely gave them positive feedback. There is no difference between the two in preference rating.

Higher learning rates to positive reinforcement reflect vigilance to reinforcement contingencies. This is indicated by a rapid change in behaviour when contingencies were reversed. Adolescents show lower positive learning rates compared to children and adults.

Adolescents showed greater activity in the supplementary motor cortex and in the putamen when receiving positive social reinforcement. Elevated activity within a motor circuit in adolescents when receiving positive social feedback is associated with speeding responses to cues of the least reinforcing peer.

Different amounts of positive social reinforcement enhanced learning in children and adults. However, all positive social reinforcement equally motivated adolescents (i.e. lower positive learning rate). They show elevated activity in response planning circuitry when they receive positive feedback, regardless of the expected outcome. This reiterates that adolescence is a period of unique sensitivity to peers. Adolescents may have an overall vigilance to peer approval. This demonstrates that peers can enhance adolescents’ risk-taking behaviour.

The lower positive learning rates for adolescents could occur if adolescents do not learn to discriminate between the cues that are associated with different amounts of positive social feedback. Alternatively, adolescents’ behaviour may not be captured by simple reinforcement learning.

Adolescents may also have a lower positive learning rate due to increased motivation toward that which is socially the least reinforcing. This may be as adolescents tend to engage in risky behaviour when they perceive themselves as less socially accepted.

There is elevated activity in the insula to social cues in adolescence. The insula plays an important role in processing emotional salience. There is more activity in response planning circuitry (i.e. putamen; supplementary motor area) when adolescents receive positive feedback. This may demonstrate that peer approval motivates adolescents toward action. Greater premotor activity at the time of receiving positive feedback and faster response times to the cue of the least reinforcing peer may suggest a heightened motivation in the adolescent for peer approval.

The heightened activity in the insular cortex and regions within response planning circuitry of adolescents suggest an affective-motivational sensitivity toward any peer approval. There is increased sensitivity in affective-motivational circuitry in early versus late adolescence. Social sensitivity decreases in late adolescence.

There are adolescent-specific increases in the motivational salience of peers. This influences neural circuitry function and this, in turn, increases sensitivity to peer approval and learning in the adolescent.