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You make your best friends in your late adolescence

What happens in young people's brains when they win money for someone else? Psychologist Elisabeth Schreuders has shown that the brain responds differently according to the type of friendship and that the response is strongest with stable relationships later in adolescence. PhD defence on 6 March.

Developmental psychologist Schreuders is interested in the age range of 8-29. She used the fMRI scanner at the LUMC to measure the brain activity of people of different ages a number of times in various money games in the fMRI scanner in the LUMC. Schreuders: ‘All participants were invited along three times; otherwise you don’t know if a development is continuing. That is the advantage of research over a longer period of time, as in the project “Braintime – the growing brain’ project” that this study is part of.’

Win money

The research participant played a game in which they had to bet on heads or tails. If they were right, they won and if they were wrong they lost money. If the participants were winning for themselves, the researchers saw a reaction in a specific region of the brain (nucleus accumbens) that responds to rewards. The response in that region increases in participants aged between 8 and 16 and then decreases again. But why? Schreuders: ‘The increasing activity is linked to motivation and personal goals. The decreasing activity is linked to how much you like to win, and that has more to do with the situation itself. What is happening socially is actually more interesting. Because how does the brain activity in the brain region for reward change if the participants win money for their best friend?’  

From ‘peers’ to ‘best friends’

Participants who chose a different best friend each year were compared with participants who chose the same friend for three consecutive years. In these participants with stable friends, the brain activity first increases and then decreases. Their relationship is good throughout adolescence. This changing brain activity was not apparent in unstable friendships; here the friendship declines with age. The brain activity of participants with stable friendships until the late adolescence shows that there is a sensitive period for the development of best friendships. A caveat from Schreuers: ‘All these young people have best friends, so they are doing well socially. I do think that it is more important to expand your social network in early adolescence and only then to become best friends with someone. So first peers, then best friends.’

Making social decisions

Schreuders studied prosocial behaviour in young people and adults that serves to strengthen social ties. Here the participants played a game in which they had to give coins to a friend or another acquaintance, neutral or unknown. The question is whether they were willing to share. Both groups were prosocial to friends and less social to people they didn’t like. There was a difference in how often adults made prosocial choices for friends. The brain activity of adults who were less prosocial in this differed. They did activate the same regions but more strongly the regions that previous research showed a link with conflict situations and transgressing social norms. Schreuders thinks this could be a kind of alarm: ‘Adults whose behaviour is least in accordance with prevailing social norms have a stronger signal in those regions (the supplementary motor area in the insula anterior). Because they know that this isn’t right, but choose for themselves more frequently anyway.

Social environment

Schreuders hopes to be able to build on these results for her research into how different types of friendship and peer relationships contribute to the development of young people. At Tilburg University she is going to research as postdoc how the social environment influences the development of young people. This relates to their mental and physical wellbeing. How does bullying affect your emotional development, for instance? And how does the immune system react to this, with any long-term effects? Schreuders: ‘In our two big Startimpuls projects in the NeuroLabNL route of the National Science Agenda we are working together with other universities and partners. That is why we can deliver tangible products, and we are also thinking of interventions.’

Photo: Don LaVange / Flickr
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