What is this article about?

Humans are highly social compared to other species. Even 1-year-old toddlers help others. This social behaviour keeps developing and becomes increasingly complex with age. For example, preschoolers mainly use lies for their own benefits, while school-aged children start to lie to protect other’s feelings (white lies).

Developmental changes in social behaviour are related to developmental changes in cognitive functions, such as perspective taking and impulse control. In the current chapter, evidence for the hypothesis that the gradual development of impulse control and perspective-taking skills are related with more strategic thinking and increased incorporation of other’s intentions in social decision-making.

Why use economic games?

Economic games were introduced by behavioural economics. These are used to study psychological and neural mechanisms that underlie social decision-making. Examples are the Ultimatum Game and the Dictator Game. In these games, there are two players. In the Ultimatum Game, one player is given a reward (money, food or anything else). This person is the ‘proposer’, and proposes to split his reward with another player, the ‘responder’. If the responder accepts the proposal, both players receive what was proposed. If the responder rejects, then none of the players receives any reward. In the Dictator Game, the responder is not able to reject the proposal, and thus only receives the amount that the proposer transfers. An assumption of Game theoretical models is that all players should accept all proposals that are above 0, because any free reward would be beneficial. However, this is not true. These games have shown that people do not only care about maximizing their outcomes, they also seem to care about others. For example, in the Dictator Game, the proposer often transfers on average 20-30% of their stakes to the responder, even though they do not have to. In the Ultimatum Game, proposers often choose for an equal split of their stake and responders usually reject offers that are smaller than 20% of the stake. It has also been shown that people do not like to receive less than the proposer, which is called disadvantageous inequity aversion. When people then reject the offer, this might serve as a way to ‘correct’ the inequity.

These paradigms are useful, because they can be used to determine differences between age groups. They also make it easier to quantify complex social behavior which is useful for neuroimaging research. Furthermore, these games can be manipulated so that researchers can gain more understanding of the subcomponents of social decision-making.

How does a preference for fairness develop?

Toddlers are reluctant to engage in prosocial behavior when it is costly to themselves. Studies employing the Dictator Game have shown that although children tend to keep most of the resources to themselves, the size of their donations increase between the ages of 3 and 8. By the age of 9, their donations do not differ from donations made by adults. Thus, there is an increase in costly sharing. This is not due to differences in knowledge about what is fair; infants as young as 15 months already expect resources to be distributed equally. Even though 3-year-olds do not differ from 8-year-olds in beliefs about equal division of rewards, they still keep more than 50% of the rewards to themselves in a Dictator Game. During this age, the willingness to send rewards increases. This means that a developing sense of fairness leads to that children engage in more equal splits.

In addition to fairness considerations, there are also strategic concerns. For instance, adults offer higher shares of the stake when they know that the second player can punish (reject) unfair offers. One can thus look at differences in the Ultimatum Game and Dictator Game as a measure of strategic social behavior. During late childhood (7-10 years), children make higher Ultimatum Game proposals compared to Dictator Game proposals, but their proposals are still smaller than those proposed by adults. During adolescence, the difference between the two games becomes greater, which means that there is a developmental increase in strategic behavior across adolescence. In sum, the prosocial tendency to share with others emerges early, but social behavior becomes increasingly strategic across childhood and adolescence.

What are the cognitive mechanisms underlying developmental change in strategic social behavior?

It has been shown that strategic social behavior is dependent on the capacity to implement behavioral control; a selfish impulse (keeping all resources to oneself) has to be controlled. Proposers also need to be able to take the responder’s perspective into account, to predict what proposals they might accept or reject. This perspective-taking is often called ‘theory of mind’, which young children often are not capable of. In sum, behavioral studies that have employed these game paradigms show that cognitive development which are both related to impulse control and perspective taking play a crucial role in understanding age-related changes in social behavior.

What neural networks are involved in social decision-making?

There are three brain networks which are important in social decision-making: a basic affective network, a cognitive regulatory network, and a ‘mentalizing’ network. The basic affective network consists of the anterior insula, ventral striatum, and the amygdala. These determine whether social stimuli should be approached (positive affect) or avoided (negative affect). Increasing activity in the insula has been related to unreciprocated trust and receiving unfair offers. These brain regions interact with a cognitive regulatory network which consists of the dorsal anterior cingulate cortex (dACC), and regions in the prefrontal cortex (PFC), such as the ventrolateral prefrontal cortex (vIPFC) and the dorsolateral prefrontal cortex (dlPFC). These areas are related to cognitive control over impulses and can help individuals to act in a goal-directed manner when they experience a conflict between self-interest and social norms. These control-related areas are thus crucial for the regulation of strategic social behavior. Both the affective and control regions interact with a third system, the ‘mentalizing’ network. This includes the left and right temporoparietal junction (TPJ), superior temporal sulci, ventral, and dorsal regions of the medial PFC and the temporal poles. These regions are often active in tasks that involve thinking about other people’s mental states, when people have to infer other people’s thoughts, beliefs or desires. Lastly, taking other people’s perspectives in economic games has been associated with activation in regions of the mentalizing network, such as the TPJ and the dorsomedial PFC.

How can we understand social behavior from a developmental neuroscience perspective?

It has been shown that different brain regions mature at different ages. Sensorimotor regions in the occipital and parietal lobes mature first. The dlPFC and the TPJ are the latest brain regions to fully mature, which might explain the protracted developmental pattern in associated functions such as cognitive control and perspective taking. Affective networks mature early, while regions of the cognitive regulatory network mature late. This can explain why affective reactions to unfairness are visible early in development and why strategic considerations during social decision-making develops later. This is in line with studies that have shown that detection of violations of fairness and neural responses in the insula and the dACC mature before adolescence, and that intentionality understanding in fairness decisions develops across adolescence and is related with neural activity that are important for perspective taking (TPJ) and impulse control (dlPFC). It has been suggested that early adolescents tend to make more self-oriented choices, while late adolescents tend to make more other-oriented choices. This is due to differences in the development of the dmPFC and the TPJ.