Social decision‐making in the brain: Input‐state‐output modelling reveals patterns of effective connectivity underlying reciprocal choices

Abstract

During social interactions, decision‐making involves mutual reciprocity—each individual's choices are simultaneously a consequence of, and antecedent to those of their interaction partner. Neuroeconomic research has begun to unveil the brain networks underpinning social decision‐making, but we know little about the patterns of neural connectivity within them that give rise to reciprocal choices. To investigate this, the present study measured the behaviour and brain function of pairs of individuals (N = 66) whilst they played multiple rounds of economic exchange comprising an iterated ultimatum game. During these exchanges, both players could attempt to maximise their overall monetary gain by reciprocating their opponent's prior behaviour—they could promote generosity by rewarding it, and/or discourage unfair play through retaliation. By adapting a model of reciprocity from experimental economics, we show that players' choices on each exchange are captured accurately by estimating their expected utility (EU) as a reciprocal reaction to their opponent's prior behaviour. We then demonstrate neural responses that map onto these reciprocal choices in two brain regions implicated in social decision‐making: right anterior insula (AI) and anterior/anterior‐mid cingulate cortex (aMCC). Finally, with behavioural Dynamic Causal Modelling, we identified player‐specific patterns of effective connectivity between these brain regions with which we estimated each player's choices with over 70% accuracy; namely, bidirectional connections between AI and aMCC that are modulated differentially by estimates of EU from our reciprocity model. This input‐state‐output modelling procedure therefore reveals systematic brain–behaviour relationships associated with the reciprocal choices characterising interactive social decision‐making.

Altered social decision making in patients with chronic pain

“…Activation of the insula is stronger during the processing of unfair as compared to fair offers (Corradi-Dell'Acqua, Tusche, Vuilleumier, & Singer, 2016 ; Sanfey, Rilling, Aronson, Nystrom, & Cohen, 2003 ), and predicts offer rejection (Feng, Luo, & Krueger, 2015 ; Guo et al, 2013 ; Hollmann et al, 2011 ). And, effective connectivity between the insula and the anterior midcingulate cortex was linked to individuals’ reciprocity in a social interaction task (Shaw et al, 2019 ). Furthermore, lesions to the insula are associated with decreased inequity aversion (Nitsch, Strenger, Knecht, & Studer, 2021 ).…”

Dissecting social interaction: dual-fMRI reveals patterns of interpersonal brain-behavior relationships that dissociate among dimensions of social exchange

“…In many interactive paradigms used for hyperscanning studies, such as those employing economic games (e.g. ultimatum game; Shaw et al 2018; 2019), the asymmetry of player roles is enforced by the very nature of the task. In others, however, such asymmetry is allowed to emerge spontaneously; in the synchronized finger-tapping task used by Konvalinka et al (2014), for example, pairs of participants either mutually adjusted to each other or followed a computer metronome.…”

Effect of facial expression on decision making

“…The relationship between emotion and decision-making has been addressed from multiple perspectives ranging from philosophy (Solomon, 1993) through to neuroscience (Phelps et al, 2014). A study has been conducted of the neuronal and cognitive mechanisms that underpin this relationship within a social context in which decision-making involves mutual reciprocity; in other words, the options chosen within the context of social interaction are the consequence or antecedent of choices made by other people, thereby revealing the relationships between the brain and behaviour (Shaw et al, 2019). The ultimatum game is a good example of this kind of interaction and of the significant role emotions play (Tamarit & Sánchez, 2016).…”