The "Who" System of the Human Brain: A System for Social Cognition About the Self and Others

Abstract

Neuroscientists are fond of talking about brain systems for the processing of "what" and "where" information about objects and their locations. What is critically missing is the concept of a "who" system dedicated to the neural processing of information about social agents-both the self and others-and their interactions. I propose here the characterization of such a system, one that functions not only in perception but in production as well, such as when recounting stories about oneself and others. The most human-specific features of the "who" system are two complementary systems that I refer to as the other-as-self mechanism and the self-as-other mechanism. The major function of the other-as-self mechanism is to perceive other people egocentrically as proxies of the self, as occurs through the processes of mentalizing and empathizing in both everyday life and in the experience of the theatrical and literary arts. The major function of the self-as-other mechanism is to overtly depict other people during acts of communication through vocal and gestural processes of mimicry, such as occurs during quotation in conversation and through acting in the theatrical arts. Overall, the "who" system of the human brain mediates both perceptual and behavioral aspects of social cognition, and establishes the existential distinction between self and other in human cognition. I present neural models for the instantiation of the "who" system in the human brain and conclude with a discussion of how narrative serves as a foundation for human cognition more generally, what I refer to as narrative-based cognition.

Keywords: brain; character; mentalizing; mimicry; narrative; other; self; theory-of-mind.

Figure 1

The “standard” mode of social cognition. The standard mode of social cognition is defined as that mode in which the self is processed egocentrically and the other is processed allocentrically, both in perception and production.

Figure 2

The other-as-self mechanism. The principal other-as-self mechanism is found in perception (top panel): perceiving others egocentrically through mentalizing processes. A second, though uncommon, mechanism is found in production (bottom panel): producing the self allocentrically. This can occur as a projection of the self onto a self-avatar or other object, for example in virtual reality applications. The term “object” is used here to refer to either a physical or virtual representation of the self.

Figure 3

The self-as-other mechanism. The principal self-as-other mechanism involves portraying others egocentrically through mimicry and acting (top panel). A second, though uncommon, mechanism involves producing others allocentrically (bottom panel). This can occur as a portrayal of another person using an object, for example a dummy in ventriloquism or an avatar in role-playing video games. The term “object” is used here to refer to either a physical or virtual representation of another person.

Figure 4

Summary of the narrative mode of social cognition. The principal other-as-self mechanism involves perceiving others egocentrically through mentalizing and empathy. A production counterpart occurs in the form of narration. A second mechanism works in production to represent the self allocentrically using objects such as avatars. The principal self-as-other mechanism involves portraying the other egocentrically through mimicry, acting, and occasionally spirit possession. A second mechanism works to portray others allocentrically using objects, such as puppets and avatars. The figure uses shading and arrows to provide an approximate representation of the dynamics of self and other processing for each mechanism. In mentalizing, empathy, and narration, the self reaches out psychologically to an other’s mind. In the use of self-avatars, the self gets projected onto an object. In mimicry, acting, and possession, an other comes to inhabit the self’s body during a performance. In the use of other-avatars, the portrayal of an “other” occurs using an object, rather than the self’s body. Note that the processes shown horizontally on either side of the central vertical divider are not meant to be paired with one another; the organization is arbitrary.

Figure 5

A neural model of the “who” system of the human brain. While “who” processing involves all facets of sensory processing about physical features and movement across the five major senses, the core of the who system is a network for character processing. It maps onto systems for mentalizing, trait processing, emotion perception, and emotional appraisal. The mentalizing components include the ventromedial prefrontal cortex (vmPFC), posterior cingulate cortex (PCC), precuneus, and the cortex of the temporoparietal junction (TPJ), which acts as a hub that interfaces areas for processing emotional appraisals [orbitofrontal cortex (OFC), insula, and amygdala (amyg.)] and the perception of emotional expression (the posterior superior temporal sulcus, pSTS), as well as episode processing for plot-schemas that is not shown in the figure. Trait processing includes areas in the dorsomedial prefrontal cortex (dmPFC). Components of the mentalizing system are shown in green, while sensory and emotion areas are shown in red. The figure is oriented anatomically such that the left side of the figure corresponds with the anterior part of the brain. Abbreviation: Emot., emotional.

Figure 6

Narrative-based cognition (NBC). The left half of the figure presents a model of cognition based on narrative notions of plot-schemas. This is contrasted with the standard conception of stories in the right half of the figure, where stories are told during acts of communication and deal with past events that are already completed. In the case of cognition, the narratives are internal “stories in the making,” as represented by the incomplete shading inside the plot box. The brackets for [End] suggest that the ending of the story has not yet occurred and can only be simulated by the person through episodic future thinking. Because cognition deals with ongoing narratives, the major focus is on future planning for goal-directed actions, hence prospection. Once such goal-directed plots are completed, they can become reportable as told stories about past events. Abbreviations: Beg, beginning; Mid, middle.

Figure 7

The integration of character and plot in human cognition. The figure integrates information from Figure 4 about the standard and narrative modes of cognition with information from Figure 6 about embodied plot-schemas into a concept of NBC that unifies character and plot in human cognition.