Flocking together and thinking apart: Gendered friendships and decision-making in adolescence

Information about yourself

I am professor of developmental psychology at University College London (UCL) and have a strong interest in understanding the causes of children’s emotional and behavioural problems. I search for causes in biological and cognitive factors, but also in the family environment (parenting, parental mental illness and poverty) and the broader physical and social environment. 

Tell us a little about the background to the study, the methods used and why

Our study used the Millennium Cohort Study, a population-based longitudinal study of a cohort born in the UK in 2000–2002. It investigated whether decision-making (measured using the Cambridge Gambling Task (CGT)) in early and middle adolescence (ages 11 and 14, respectively) affects or is affected by the sex composition of a young person’s friendship group. We were interested in the anatomy of decision-making for early and middle adolescence because this is when young people are increasingly making decisions for themselves. This is also the age when the influence of peers may eclipse that of the immediate family and reinforce gender identity. As to the focus on the role of sex and gender, decision-making is generally considered gendered. There is also evidence for the importance of the sex composition of an adolescent’s friendship group for risk-taking but also other aspects of decision-making. However, the opposite direction in the link has yet to be studied: whether an adolescent’s style of decision-making can ‘predict’ the sex composition of their friendship group. Ours was the first study to explore the potential reciprocal associations between an adolescent’s ‘objectively measured’ decision-making and the sex composition of his or her friendship group.

In terms of research hypotheses, we expected that females in mixed-sex or other-sex friendship groups would score significantly higher in risk-taking and lower in quality of decision-making and risk adjustment compared to females with predominantly female peers. We also investigated whether the sex of friends may reflect preferences arising from the young person’s style of decision-making. We expected youths showing lower quality of decision-making and those more sensitive to reward (i.e., those scoring higher on risk-taking) to find themselves, later in adolescence, in other- or mixed-sex peer groups.

What were the key findings and their implications?

As expected, sex segregation was the norm and, interestingly, increased significantly over time: boys reported having predominantly male friends (49% at age 11 and 85% at age 14) and girls predominantly female friends (41% at age 11 and 88% at age 14). As for the association between decision-making and the sex composition of the friendship group, the strongest link we found was for girls whose friends were mainly girls at 11, who showed advantageous performance on four out of the five CGT measures at age 14. Otherwise, the paths from the sex of one’s friends to one’s decision-making, even when significant, were not strong. Risk-taking, the CGT outcome measure which showed the most difference between girls and boys, was not affected by the sex of friends. Our findings for girls chime with those of previous studies showing that any benefits of sex segregation of contexts in adolescence tend to be seen in females. In terms of the other direction, there were some significant associations between decision-making at 11 and the sex composition of the friendship group at 14, which varied by the sex of the cohort member. For boys, longer deliberation time at 11 mildly reduced the chances of being in a group predominantly of their own sex at 14, while better quality of decision-making at 11 reduced the chances of having mainly other-sex friendships at 14. For girls, delay aversion at 11 was associated with other-sex friendships at 14.

Our findings carry implications for practitioners and parents. Those of them who anticipate or must be prepared to mitigate adolescent risky behaviour – such as smoking, other substance abuse or delinquency – may be interested that we did not find an association between risk-taking and keeping company with boys. Risk-taking, though higher in boys, was not associated with the sex of friends, in either boys or girls. However, other aspects of decision-making tended to be particularly favourable among girls who were already in mainly-girl friendship groups at 11. Educators may want to exploit the positive dynamics in girls’ own-sex friendship groups and be sensitive to the needs of other girls and boys for support in the development of their decision-making.

Why did you choose CANTAB for your study?

Measuring reward-processing longitudinally and in a large general-population sample of children was truly unique, and CANTAB’s CGT is the tool that allowed us to do this. CGT is a neurocognitive measure proven to be sensitive to deficits in reward-based decision-making and is considered a relatively pure measure of reward-based decision-making with explicit outcome probabilities.

Are there any future areas of investigation that could follow your research?

We are currently using the CGT for another project, also with data from the Millennium Cohort Study.

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