A dual-fMRI investigation of the iterated Ultimatum Game reveals that reciprocal behaviour is associated with neural alignment.

Abstract

Dyadic interactions often involve a dynamic process of mutual reciprocity; to steer a series of exchanges towards a desired outcome, both interactants must adapt their own behaviour according to that of their interaction partner. Understanding the brain processes behind such bidirectional reciprocity is therefore central to social neuroscience, but this requires measurement of both individuals’ brains during real-world exchanges. We achieved this by performing functional magnetic resonance imaging (fMRI) on pairs of male individuals simultaneously while they interacted in a modified iterated Ultimatum Game (iUG). In this modification, both players could express their intent and maximise their own monetary gain by reciprocating their partner’s behaviour – they could promote generosity through cooperation and/or discourage unfair play with retaliation. By developing a novel model of reciprocity adapted from behavioural economics, we then show that each player’s choices can be predicted accurately by estimating expected utility (EU) not only in terms of immediate payoff, but also as a reaction to their opponent’s prior behaviour. Finally, for the first time we reveal that brain signals implicated in social decision making are modulated by these estimates of EU, and become correlated more strongly between interacting players who reciprocate one another.

Revealing the Neurobiology Underlying Interpersonal Neural Synchronization with Multimodal Data Fusion

“…Searching for an extensive list of INS-related terms (Supplement 1.1.1), the initial literature search resulted in 2,575 unique records from which 79 publications were found eligible for metaanalysis (Figure 2A for exclusion reasons). Finally, we included 14 hyperscanning fMRI publications (Bilek et al, 2015; Gordon et al, 2021; Koike et al, 2016; Koike, Sumiya, et al, 2019; Koike, Tanabe, et al, 2019; Miyata et al, 2021; Saito et al, 2010; Salazar et al, 2021; Shaw et al, 2018, 2020; Spiegelhalder et al, 2014; Špiláková et al, 2020; L.-S. Wang et al, 2022; Xie et al, 2020; Yoshioka et al, 2021), 8 pseudohyperscanning fMRI publications (Anders et al, 2011; Dikker et al, 2014; Kostorz et al, 2020; Liu et al, 2021, 2022; Silbert et al, 2014; Smirnov et al, 2019; Stephens et al, 2010), 54 hyperscanning fNIRS publications, and 3 pseudohyperscanning fNIRS publications [Figure 2B (interactive version available online), see Tables S1 and S2 for detailed information and fNIRS references]. INS foci coordinates were extracted from the above publications, requested from the authors, drawn from a virtual registration database (Tsuzuki et al, 2007), or derived from manual reconstruction of fNIRS probe setups (Aasted et al, 2015).…”

“…Searching for an extensive list of INS-related terms (Supplement S2.0.1), the initial literature search resulted in 2,575 unique records from which 79 publications were found eligible for meta-analysis (Figure 2A for exclusion reasons). Finally, we included 14 hyperscanning fMRI publications (2,27,29,(48)(49)(50)(51)(52)(53)(54)(55)(56)(57)(58)(59), 8 pseudohyperscanning fMRI publications (13,(60)(61)(62)(63)(64)(65)(66), 54 hyperscanning fNIRS publications , and 3 pseudohyperscanning fNIRS publications (121)(122)(123) [Figure 2B (interactive version available online), Tables S1 and S2]. INS foci coordinates were extracted from the above publications, requested from the authors, drawn from a virtual registration database (124), or derived from manual reconstruction of fNIRS probe setups (125).…”

Simultaneous functional MRI of two awake marmosets

“…In humans, mutual interaction during eye contact has been shown to be mediated by the limbic mirror system, including the ACC and anterior insular cortex (AIC) 53 . Furthermore, inter-brain synchrony has been found in regions including the ACC and right AIC when playing a modified interactive ultimatum game 54 . Taken together, correlated activity in area 24 (a part of the anterior and middle cingulate cortex) and the temporal region infers a synchronization of regional brain activity due to the presence of a visual conspecific.…”

Lesion evidence for a causal role of the insula in aversion to social inequity

“…(2012) found that two distinct networks are anchored in the right anterior insula: a network related to the intensity of affective experience and a network associated with attention and performance speed. In the context of social decision-making, a recent study by Shaw et al. (2018) identified effective connectivity between the anterior insula and the anterior midcingulate cortex as a neural correlate of individuals’ reciprocity.…”

“…, 2013 ; Feng et al. , 2015 ), and effective connectivity between the anterior insula and the anterior midcingulate cortex was found to correlate with individuals’ reciprocity in a social interaction task ( Shaw et al. , 2018 ).…”