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A little aggression helps children in their social development, Simone Dobbelaar discovered during her PhD

Is aggression always bad? PhD research by psychologist Simone Dobbelaar shows that it is not. In fact, children who occasionally fiercely defend themselves and stand up for their peers often feel better mentally.

@EACrone: Simone Dobbelaar (right) with her dissertation 'Helping Me, Helping You' and supervisor Eveline Crone.
@EACrone: Simone Dobbelaar (right) with her dissertation 'Helping Me, Helping You' and supervisor Eveline Crone.

A disapproving look from a friend at your new shoes, no invitation to that party or just a firm 'no' when you ask if you can join in a game. ‘We face rejection from an early age,' says Simone Dobbelaar. 'Being rejected is a recognisable, universal feeling, but everyone deals with it differently.' One child will give a fierce snarl back, while another child will walk away quietly. 'I wanted to find out how that works.'

So for her PhD project, she investigated how children over the years respond to social evaluation (approval and rejection by another person) and how this behaviour is related to their social competence (the ability to achieve social goals for yourself and others). Dobbelaar: 'How aggressively or pro-socially do children act after receiving feedback? How is this behaviour related to other factors, e.g. parents' parenting style? And what brain processes play a role in this?'

About the study

Dobbelaars research was part of the large-scale L-CID Twin study led by Eveline Crone. In this study, Leiden neuropsychologists follow the development of social competences and behavioural control in twins aged between three and 14 years old. On 26 October 2023, she successfully defended her dissertation 'Helping Me, Helping You'. 

The research takes place within the Leiden Consortium on Individual Development. Dobbelaar is also part of the Society, Youth and Neuroscience Connected lab at Erasmus Rotterdam (SYNC Lab)

Hundreds of twins

For six years, Dobbelaar and her colleagues studied some five hundred twins between the ages of 7 and 13. Dobbelaar herself has a twin sister: 'Twins share approximately 50% of their DNA, with identical twins sharing it completely. Furthermore, twins are raised in the same environment, making it possible to determine whether specific behaviours are predominantly genetic or shaped by environmental factors.'

'With all those braces, they weren't able to go into the MRI scanner anymore' 

Every two years, the twins underwent MRI scans while performing various tasks to measure their brain activity. Dobbelaar adds with a laugh, 'Of course, after a few years, many of them were fitted with braces, which meant they could no longer go in the scanner. However, as we had started with a large group, we were fortunate to have enough participants remaining by the end of the study.' 

Dobbelaar examines a child in LUMC's MRI scanner during corona time, in May 2021.

Friendship books

Inside the MRI scanner, the children received feedback based on answers they had previously entered in a friendship book. This feedback involved showing them a picture of a peer with either a thumbs up or down, and a third option was a grey circle indicating a neutral response. After this, the child had the choice to send an unpleasant, harsh sound to the individual who provided the feedback, as a kind of revenge. The longer a child continued to send the harsh sound, the more aggressive their response became. Dobbelaar notes, While they were transmitting the sound, we monitored their brain activity closely.

Ball game

The children then engaged in a virtual game while in the scanner, where they tossed a ball with three other players. At a point in time determined by the researchers, one of the three players was deliberately left out. The child in the scanner then had the option of throwing the ball to the excluded child more frequently. Through this, Dobbelaar assessed the children's social responsiveness, examining whether they were sensitive to the exclusion of others or chose to disregard it.

'How did children react to being excluded from others?' 

Drawing with parents

For the third task, children participated in a drawing task together with their parents. During this task, Dobbelaar and her colleagues observed the parents' interaction with their child, noting how sensitively they engaged with them. A sensitive parent actively pays attention to the child's needs and responds accordingly. This might involve asking questions like, How should we approach this together? and allowing room for the child's ideas.’

Learned young

Children whose parents responded sensitively to their needs also showed less aggressive behaviour in the MRI scanner. 'This correlation was only seen at a young age, but we did not see it in adolescence.

'In addition, we saw that children who had more activity in the dorsolateral prefrontal cortex contained their aggression better and sent back fewer loud noises after receiving feedback. In general, the older children became, the more mildly they responded to feedback. It seems you learn how to regulate your aggression at a relatively young age.'

Helping me, helping you

Remarkably, Dobbelaar also discovered that an aggressive response doesn’t necessarily have to be bad. Children who returned loud noises in the MRI scanner, as well as behaving more socially towards others in the virtual ball game, had a higher mental well-being a year later and showed less problem behaviour. These children responded more strongly to their social environment, standing up for themselves and others. So a little aggression is not necessarily always bad if you also stand up for someone else in another context.' 

'A little aggression is not necessarily always bad if you also stand up for someone else in another context.' 

This is why Dobbelaar argues in her dissertation that researchers, but also parents and teachers, for example, should adopt a broader perspective. 'Of course, aggressive behaviour should not get out of hand. Nor is it the case that children who are less aggressive become less happy later on. Those factors are still very changeable. But certain behaviour, like aggression or helping someone, can be very appropriate. In one context you help yourself with it, in another context the other person. That’s the reason for the title of my dissertation: Helping me, helping you.'

Researching new friendships

The dissertation was the culmination of years of PhD work. 'Whenever I told people I was doing a PhD, the response I got was often: Oh, then you’ll be spending the next four years on your own, writing.” I didn't have that experience at all. In our lab, we worked together a lot and I was inspired by how colleagues approached their studies and by the positive atmosphere. It was reassuring to know that if I got stuck, I had an entire team to fall back on. For me it was a fantastic experience.'

'Spending four years on your own, writing? That's not how I experienced my PhD at all.'

That explains why she will soon start work as a postdoc. 'I'll be joining the GUTS project, collaborating within Berna Güroglu's research group, focusing on a cohort of young individuals who are in the early stages of building relationships, such as those in sports clubs or student unions. We’re going to delve into their social dynamics, how they form friendships, and how their brains develops. I'm really excited to be able to explore this entirely new target group.' There’ll be fewer braces in this group, so MRI scanning will be a lot easier.

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