Social Neuroscience of Self-categorization
The study of neural processes underlying representation of social group membership.
Self-categorization is a cognitive process of perceiving both oneself and others in terms of collective entities (social groups or categories) rather than in terms of individual characteristics and personality. Development of new methods of the brain research allows studying self-categorization at the neural level. Self-categorization became one of the key issues in a new scientific discipline, social neuroscience, which is an interdisciplinary field of research on the intersection of neuroscience and social psychology studying neural basis and mechanisms of social cognition, emotions, and behaviors.
Self-categorization in Social Psychology
Self-categorization refers to social categorization, i.e., classifying individuals into social groups or categories, from an ego-centric perspective. This means that not only social world is classified and typified during social categorization but also that an individual is positioned in this social world and describes him/herself in terms of membership in specific social groups or categories such as ethnicity, race, gender, age, political preferences, family. The outcome of self-categorization is the formation of specific social identity, which is a part of the self-concept, representing knowledge and feelings of their group as well as its psychological value. Key theories of social psychology, namely, Social Identity Theory and Self-Categorization Theory (Turner and Reynolds 2003), treat self-categorization and social identity as the basis of intergroup relations and associated perceptions, attitudes, and behaviors.
During social categorization, individuals tend to focus on similarities within groups and differences between groups, thus maintaining and reinforcing group boundaries. Studies in social psychology showed that individuals differently respond to social groups with which they associate themselves, i.e., ingroups, and all other, i.e., outgroups. These effects include asymmetrical responses to in- and outgroups at cognitive, affective, and behavioral level. Perceived group differences affect attention, memory, judgments, evaluations, empathy, motor predispositions, and allocation of resources. Social psychology treats these asymmetries as a source of many problematic aspects of intergroup relations such as prejudice, discrimination, intergroup conflicts.
Evolutionary, social categorization is considered as an important tool for social species. Living in collectives requires ability to make fast and accurate identification of social agents and infer their intentions. Establishing alliances is crucial for survival and the necessity to detect allies should lead to development of effective skills in social cognition. Affiliation with a group is necessary to satisfy social needs such as sense of belonging and self-esteem. Studies in primatology show that nonhuman primates have well-developed social cognitive skills and share basic predisposition to form and detect various social groups as well as form preferences for the members of their own group, the so-called ingroup favoritism.
The Social Neuroscience Approach to Self-categorization
Evolutionary significance of social categorization implies that the ability to effectively classify and automatically respond to different types of social objects must be supported by specialized biological systems and mechanisms: genetic, physiological, and neural. The progress in neuroscience provided social psychologists with new research tools to study social categorization. Among them, functional magnetic resonance imaging (fMRI) and electroencephalography (EEG) became the two most actively used. Whereas the first one helps to identify neural systems involved in various aspects of social categorization, the second one allows effective tracing the time-course of social cognitive and affective responses during social categorization. Other research methods that can be used in social neuroscience of self-categorization include magnetoencephalography, transcranial magnetic stimulation, administration of “social” hormones such as oxytocin and testosterone, lesion studies, animal models, and some other.
The Brain Structures Involved in Neural Processing of Self-categorization
Studies in social neuroscience revealed several brain regions, which are especially important for social categorization and representation of social identity (Cikara and Van Bavel 2014; Molenberghs 2013; Shkurko 2013).
Amygdala, a part of the brain’s limbic structure, was initially associated with fear conditioning and fast negative response to the members of racial outgroups. Later studies showed that it can be selectively activated in response to ingroup member as well. Currently, the role of amygdala in social categorization is associated with the detection and emotional arousal in response of socially relevant stimuli. In different contexts, both in- and outgroups can be motivationally significant and evoke selective activation of amygdala.
Medial prefrontal cortex (mPFC), a frontal part of the cerebral cortex, is involved in several higher-order social cognitive processes which include mentalizing (taking the perspective of other individuals), processing self-relevant information, and cognitive empathy. Particularly, mPFC demonstrates greater activation in response to ingroup members and self-referential thinking as compared to mentalizing about outgroup members, thus supporting the view that social identity is a part of individuals’ self-concept. Extreme outgroups such as homeless people, on the contrary, may not elicit activation of mPFC during mentalizing tasks, thus indicating “dehumanization” of such social groups.
Anterior cingulate cortex (ACC) plays an important role in affective regulation. Specifically, parts of this brain structure were found to support affective empathy toward ingroup members and suppression of negative emotions in response to outgroup members.
Temporoparietal junction (TPJ) is important for mentalizing and may be involved in the construction of ingroup via perceived similarity with oneself and result in greater ingroup bias.
Fusiform gyrus (FG) and fusiform face area (FFA) are traditionally associated with perceptual expertise and sensitivity to facial stimuli, which are one the most important source of socially relevant information. Activation in FFA is associated with the better memory for ingroup faces. This finding is consistent with the idea that self-categorization lead to greater attention and individuation of ingroup members. There is evidence that FG is flexibly involved in social categorization and is subject to top-down regulation of social stimuli perception (Freeman et al. 2010). Particularly, preexistent high-level knowledge of social categories may modulate perception of social sensory input.
The human reward processing system, which includes ventral striatum (VS), dorsal striatum (DS), and orbitofrontal cortex (OFC), is also involved in several aspects of social categorization. Being sensitive to social status information and representing the value of subjectively rewarding stimuli, these regions are important for situations in which group perception is associated with the differences in status or involved in competitive relations. For example, in the context of intergroup competition, VS is activated in response to outgroup failures or misfortune, thus indicating their subjective value (schadenfreude) and group-based modulation of empathetic responses (Cikara et al. 2014; Hein et al. 2014). Some studies show that OFC can encode the value of pro-social, cooperative behavior and thus can be involved in mitigating discriminating behavior.
Insula is believed to be a part of the “pain matrix” and is involved in processing negative emotions during social categorization, although its exact role and group selectivity is not clear. For example, left anterior insula was especially responsive to the pain of ingroup members. At the same time, other studies reported activation of the right insula in response to outgroup members and its role in modulation of discriminatory behavior toward them.
Identification of the brain systems involved in social categorization is mainly the result of using fMRI technique. However, studies of hormones become increasingly important in revealing neural mechanisms related to social identity and intergroup behavior. For example, a neurohormone oxytocin known for its role in social affiliation can be sensitive to group membership. Particularly, in the social contexts in which social identity is salient, oxytocin is associated with greater ingroup love (but not outgroup hate). Exogenous administration of oxytocin and some drugs such as propranolol are considered as possible tools for interventions aimed at reducing intergroup conflicts and other negative consequences of social categorization.
Neural Processing of Self-categorization: Key Findings
Social groups are represented in the brain differently. Those groups with which an individual identifies him/herself evoke different neural responses as compared to other groups. Moreover, different ingroups and outgroups can also evoke different neural responses.
The social brain evolved to support fast and effortless reaction to different social groups. Both EEG and fMRI studies showed that the brain can detect group membership of perceived social agents within first two hundred millisecond, i.e., classify them automatically.
Asymmetrical neural responses to ingroups and outgroups were found in regard to many different cognitive, affective, and behavioral domains: visual perception, attention, memory, mentalizing, empathy, motor predispositions, judgments, evaluation, and economic decision-making.
Effects of social categorization on perception, cognition, evaluation, and behavior occur even when group boundaries are based on trivial situational and arbitrary criteria, i.e., in the so-called “minimal groups.” These effects include better face recognition of ingroup members, biased judgments, and ingroup favoritism. This means that the social brain evolved not only to facilitate fast identification of social groups but also to support cognitive biases, prejudice, and discriminatory behavior in favor of the group to which individuals belong.
Despite the importance of automatic neural responses supported by the limbic system, social categorization in humans is subject to cognitive and affective regulation processed by evolutionary more recent prefrontal cortical areas of the brain. Moreover, there is evidence that neural processing of social categorization is bidirectional and combine continual representation of actual perceptual stimuli, particularly in FFA, with higher-order discrete categories represented in other cortical regions, particularly OFC (Freeman et al. 2010).
The neural representation of social identity and group-related effects can be flexibly tuned and reconfigured in response to changes in the context, social roles taken by individual, and tasks performed. When a new identity becomes contextually salient, other identities (e.g., race) even evoking automatic biased responses can become overridden and their negative effects can be diminished.
Neural processing of self-categorization and social identity is culturally conditioned. Individuals from different cultures, e.g., individualistic and collectivistic, demonstrate differences in the representation of ingroups and various aspects of ingroup bias. For example, collectivists more than individualists involve activity in mPFC and left TPJ during representation of the personal self thus probably indicating a greater role of social identity and perspective-taking in the construction of the self (Sul et al. 2012).
The human brain evolved to effectively manage complex social relations and support group-based thinking, emotions, and behaviors. Studies in social neuroscience showed that there are no single neural system which could be directly associated with the representation of social identity and self-categorization effects. Instead, multiple systems are involved in various aspects of social categorization in a flexible and context-dependent manner. As a result, the brain is tuned for both biased and discriminatory reactions to the members of the social groups, and cognitive mechanisms supporting egalitarian responses and strategic manipulations with social identities to better fit the situation and the task needs.