How Does the Brain Infer Hidden Social Structures?

Neural signatures underlying the effect of social structure on empathy and altruistic behaviors

Humans inhabit complex social networks, monitoring social structures that encompass both direct and indirect relationships. However, previous research primarily focused on direct relationships, leaving the neural basis of how social structure influences socioemotional processes understudied. This study addressed this gap by investigating the neural pathways underlying the influence of social structure on empathy and altruistic behaviors. During fMRI scanning, participants viewed painful or non-painful stimulation to innocent strangers who shared preferences with targets who had either treated participants fairly or unfairly. Afterwards, participants rated the pain experienced by these innocents and shared money with other innocents. Participants showed reduced empathic and altruistic responses toward innocents resembling unfair (vs. fair) targets, accompanied by heightened activation in regions crucial for emotion regulation and mentalizing, such as the lateral and medial prefrontal cortex. Furthermore, whole-brain and local neural patterns in the anterior insula and premotor cortex robustly discriminated painful (but not non-painful) stimulation of different innocents, suggesting that social structure altered emotional and sensorimotor aspects of empathy. These alterations might be driven by top-down regulation, as indicated by heightened functional connectivity between the lateral prefrontal cortex and sensorimotor areas, as well as between the anterior insula and subgenual anterior cingulate cortex when witnessing the pain of innocents resembling fair (vs. unfair) targets. Together, our work is the first to uncover the neural underpinnings through which human empathy and altruistic behaviors are shaped by social structure beyond direct self-other relationships.

Similarity Among Friends Serves as a Social Prior: The Assumption That "Birds of a Feather Flock Together" Shapes Social Decisions and Relationship Beliefs

Social interactions unfold within networks of relationships. How do beliefs about others' social ties shape-and how are they shaped by-expectations about how others will behave? Here, participants joined a fictive online game-playing community and interacted with its purported members, who varied in terms of their trustworthiness and apparent relationships with one another. Participants were less trusting of partners with untrustworthy friends, even after they consistently showed themselves to be trustworthy, and were less willing to engage with them in the future. To test whether people not only expect friends to behave similarly but also expect those who behave similarly to be friends, an incidental memory test was given. Participants were exceptionally likely to falsely remember similarly behaving partners as friends. Thus, people expect friendship to predict similar behavior and vice versa. These results suggest that knowledge of social networks and others' behavioral tendencies reciprocally interact to shape social thought and behavior.

The (un)learning of social functions and its significance for mental health

Social interactions are dynamic, context-dependent, and reciprocal events that influence prospective strategies and require constant practice and adaptation. This complexity of social interactions creates several research challenges. We propose a new framework encouraging future research to investigate not only individual differences in capacities relevant for social functioning and their underlying mechanisms, but also the flexibility to adapt or update one's social abilities. We suggest three key capacities relevant for social functioning: (1) social perception, (2) sharing emotions or empathizing, and (3) mentalizing. We elaborate on how adaptations in these capacities may be investigated on behavioral and neural levels. Research on these flexible adaptations of one's social behavior is needed to specify how humans actually "learn to be social". Learning to adapt implies plasticity of the relevant brain networks involved in the underlying social processes, indicating that social abilities are malleable for different contexts. To quantify such measures, researchers need to find ways to investigate learning through dynamic changes in adaptable social paradigms and examine several factors influencing social functioning within the three aformentioned social key capacities. This framework furthers insight concerning individual differences, provides a holistic approach to social functioning, and may improve interventions for ameliorating social abilities in patients.

The Anatomy of Friendship: Neuroanatomic Homophily of the Social Brain among Classroom Friends

Homophily refers to the tendency to like similar others. Here, we ask if homophily extends to brain structure. Specifically: do children who like one another have more similar brain structures? We hypothesized that neuroanatomic similarity tied to friendship is most likely to pertain to brain regions that support social cognition. To test this hypothesis, we analyzed friendship network data from 1186 children in 49 classrooms. Within each classroom, we identified "friendship distance"-mutual friends, friends-of-friends, and more distantly connected or unconnected children. In total, 125 children (mean age = 7.57 years, 65 females) also had good quality neuroanatomic magnetic resonance imaging scans from which we extracted properties of the "social brain." We found that similarity of the social brain varied by friendship distance: mutual friends showed greater similarity in social brain networks compared with friends-of-friends (β = 0.65, t = 2.03, P = 0.045) and even more remotely connected peers (β = 0.77, t = 2.83, P = 0.006); friends-of-friends did not differ from more distantly connected peers (β = -0.13, t = -0.53, P = 0.6). We report that mutual friends have similar "social brain" networks, adding a neuroanatomic dimension to the adage that "birds of a feather flock together."

Human Representation Learning

The central theme of this review is the dynamic interaction between information selection and learning. We pose a fundamental question about this interaction: How do we learn what features of our experiences are worth learning about? In humans, this process depends on attention and memory, two cognitive functions that together constrain representations of the world to features that are relevant for goal attainment. Recent evidence suggests that the representations shaped by attention and memory are themselves inferred from experience with each task. We review this evidence and place it in the context of work that has explicitly characterized representation learning as statistical inference. We discuss how inference can be scaled to real-world decisions by approximating beliefs based on a small number of experiences. Finally, we highlight some implications of this inference process for human decision-making in social environments.

The Social Neuroscience of Prejudice

The social neuroscience approach to prejudice investigates the psychology of intergroup bias by integrating models and methods of neuroscience with the social psychology of prejudice, stereotyping, and discrimination. Here, we review major contemporary lines of inquiry, including current accounts of group-based categorization; formation and updating of prejudice and stereotypes; effects of prejudice on perception, emotion, and decision making; and the self-regulation of prejudice. In each section, we discuss key social neuroscience findings, consider interpretational challenges and connections with the behavioral literature, and highlight how they advance psychological theories of prejudice. We conclude by discussing the next-generation questions that will continue to guide the social neuroscience approach toward addressing major societal issues of prejudice and discrimination.