Social Versus Nonsocial Reasoning

This article was originally published in Brain Mapping: An Encyclopedic Reference, published by Elsevier, and the attached copy is provided by Elsevier for the author's benefit and for the benefit of the author's institution, for non-commercial research and educational use including without limitation use in instruction at your institution, sending it to specific colleagues who you know, and providing a copy to your institution’s administrator.

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Social Versus Nonsocial Reasoning K Baetens, M Vandekerckhove, and F Van Overwalle, Vrije Universiteit, Brussel, Belgium ã 2015 Elsevier Inc. All rights reserved.

Introduction Cleverness is our primary means of survival, and the human species has been stringently selected for social intelligence. The complexity of our social world was likely a major factor driving the enlargement of the human brain and, in particular, the prefrontal cortex (Dunbar, 2003). Yet, Cacioppo and Berntson’s (1992) seminal paper, often credited as the starting shot of social neuroscience, was only published at the end of the last century. With the paper, the authors struck a blow for multilevel analyses in the neurosciences, suggesting that scientific progress could be greatly accelerated by using different levels of analysis to constrain, inspire, and inform each other. They focused on social neuroscience, with the social and neuroscientific perspectives seen as two ends on a continuum of organizational levels ranging from the microlevel of genes to the macrolevel of entire cultures. The new arsenal of research methods offered by neuroscience also reinvigorated interest in the specificity of social processes: do domain-general cognitive functions, such as visual attention, semantic memory, and so on, suffice to enable our social functioning, or are there additional, uniquely social processes involved (Blakemore, Winston, & Frith, 2004)? Two decades after its starting shot, social neuroscience has become a thriving field with its own dedicated journals and hundreds of studies about the neural correlates of processes as diverse as trait inference, emotional face perception, false belief reasoning, and so on. As a relatively young discipline, the demarcation of social neuroscience is still ongoing, however, and the definition of ‘social’ employed in current research is often imprecise, if articulated at all. This ambiguity might result from the fact that it is not so easy to come up with a description of ‘socialness’ that applies to all the disparate topics involved. Mitchell (2009) noted that, while interaction is a central element in most classical definitions of social psychology, many of the contemporary topics involve intrapersonal processes (as shown by the prominent place of studies about the self). Paradoxically, these intrapersonal themes have been claimed from cognitive psychology, although themes with evident importance for social interaction (e.g., face recognition, language) have not. What motivates this counterintuitive scientific role division? Mitchell (2009) pointed out that there is a striking overlap in the neural correlates of intrapersonal processes studied in social neuroscience, notably in the medial prefrontal cortex (mPFC). Is it possible, perhaps, to define social cognitive processes based on a set of dedicated brain regions?

The Social Brain and the Specificity of Social Reasoning As discussed by Adolphs (2010), certain neural structures do seem to be exclusively dedicated to social perception, no matter what definition of ‘social’ one entertains (e.g., pheromone

Brain Mapping: An Encyclopedic Reference

receptors specifically picking up signals transmitted by conspecifics). Moving to higher-order processes such as reasoning, the picture gets blurrier. Admittedly, several reviews focused on the so-called social brain have converged on a list of the usual suspects, which populate the results tables of social neuroscience papers (e.g., Adolphs, 2009; Frith & Frith, 2010; Lieberman, 2007; Saxe, 2006; Van Overwalle, 2009; Van Overwalle & Baetens, 2009). In broad strokes, these brain regions can be situated in one of two networks: the mirror network (encompassing the anterior intraparietal sulcus and premotor cortex), which is involved in thinking about others based on concrete, sensory information (e.g., visual depiction of moving body parts or sounds typically associated with specific behaviors), and a mentalizing network (encompassing the mPFC, temporoparietal junction (TPJ), and precuneus), which is involved in interpreting more abstract conditions, when such information is not available (Van Overwalle & Baetens, 2009). Depending on one’s definition of reasoning, one could argue that both networks play an important role in social reasoning. For example, insofar as one considers goal inference based on observable actions to be a form of reasoning, the mirror network clearly plays a crucial role in such processes. Usually, however, the term is reserved for more complicated processes, especially those involving inferences based on information that is not readily observable. The mentalizing network has been consistently implicated in thoughts about others in such circumstances. But is this involvement specific to social reasoning? There is some support for the idea. Jack et al. (2013) provided evidence that social and mechanical reasoning rely on reciprocally inhibitory networks (though see Spreng, 2012). But given the multiple dissimilarities between the social and nonsocial problems in this study, it is difficult to pinpoint precisely which aspects of the stimuli or tasks result in activation differences. Researchers have attempted to rule out alternative explanations by presenting reasoning problems of identical logical form, but of different (social versus nonsocial) content. Such comparisons have quite unequivocally yielded stronger activation in the mentalizing system, notably the mPFC and TPJ (e.g., social versus nonsocial precautionary rules: Fiddick, Spampinato, & Grafman, 2005; deductive reasoning about metals or faces, Mason, Magee, Kuwabara, & Nind, 2010; false beliefs versus false photographs: Saxe & Kanwisher, 2003). More specific studies have reported the sensitivity of the mPFC to relational complexity, rather than the mere presence of intentional agents or persons in the stimulus material (Abraham, Werning, Rakoczy, Von Cramon, & Schubotz, 2008), and the TPJ is specifically more sensitive to descriptions of another’s thoughts than their physique or bodily sensations (Saxe & Powell, 2006). A lesion study has further demonstrated that this region is crucial for reasoning about the mental states of others (Samson, Apperly, Chiavarino, & Humphreys, 2004).

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Beyond the level of individual studies, Van Overwalle (2011) quantified the amount of stimulus material, referring to mental states in over 40 reasoning studies, and found a strong correlation between this measure and mPFC activation (see Figure 1). To summarize, the mentalizing network is consistently engaged in social reasoning, consistently stronger when direct comparisons with nonsocial reasoning are made, and rarely involved in studies on nonsocial reasoning. Thus, one might be tempted to assert that reasoning is not a domain-general capacity, but rather content-sensitive, as is reflected by the stronger engagement of the mentalizing network when the content is social. Indeed, as noted before, the mPFC has even been put forward as a potentially defining protagonist in social reasoning. However, some important caveats are in order, here. First, the recurrent involvement of a number of brain structures in social processes does not necessarily imply that they are preferentially, let alone exclusively, dedicated to those processes. In the case of the mirror network, this is quite clearly not the case, given that one of the striking characteristics of this network is its involvement in both the performance and observation of the same actions. Similarly, the high incidence of mentalizing network activation observed in studies on social

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Figure 1 Medial prefrontal cortex activation in reasoning is proportional to the amount of mentalizing content in the stimulus material. Adapted from Van Overwalle F (2011) A dissociation between social mentalizing and general reasoning. NeuroImage 54(2): 1589–1599, http://dx.doi.org/10.1016/j.neuroimage.2010.09.043.

reasoning might very well be correlated with a greater appeal to some domain-general process (Barrett & Satpute, 2013; Legrand & Ruby, 2009). Second, even if one finds that brain activation patterns differ according to content despite the constant logical form of the problems, the reasoning process itself might still activate exactly the same brain regions. Differences in activation may very well reflect the spontaneous processing of social content beyond task requirements. This is quite plausible, given the rich body of literature demonstrating our propensity to engage in social processing, even when this is not required by the task context (e.g., Winter & Uleman, 1984; for a review, see Uleman, Adil Saribay, & Gonzalez, 2008). These limitations should warn us against an untimely interpretation of existing research as evidence for the exclusive dedication of brain regions to social processes.

Social Reasoning Drawing Differentially on Domain-General Processes So far, we have focused on experiments looking for differential activation of the social brain by employing similar tasks focused on dissimilar content (social versus nonsocial). As noted, the interpretation of such studies poses some pitfalls. An important complimentary approach may therefore be to look for nonsocial reasoning tasks focused on nonsocial content that nevertheless results in activation of the mentalizing network. This may help to elucidate precisely what the mentalizing network contributes and whether this network is exclusively required in social reasoning. Indeed, activation in the mentalizing network, in the absence of social content or tasks, has been reported quite frequently for the TPJ and less commonly so for the dorsal mPFC (dmPFC). In a meta-analysis of the relevant studies, Decety and Lamm (2007) concluded that the TPJ is not exclusively involved in social processes, but rather it contributes to a lower-level domain-general process of attention allocation to salient stimuli (e.g., the Posner task, for overlap between social and nonsocial function within one study; see Mitchell, 2008). Nevertheless, others maintain that social and nonsocial functions involve different parts of this brain region, one part being exclusively dedicated to processing the mental contents of others and another to attention reorientation, leaving only a very limited amount of overlap (Scholz, Triantafyllou, Whitfield-Gabrieli, Brown, & Saxe, 2009). Further studies using more advanced methods may be required to settle this debate. A number of studies have reported the involvement of the dmPFC, employing conspicuously nonsocial reasoning tasks (e.g., integrating premises, Fangmeier, Knauff, Ruff, & Sloutsky, 2006; constructing narrative or causal coherence, Ferstl & Von Cramon, 2002; judging abstract > concrete properties of animals, Goldberg, Perfetti, Fiez, & Schneider, 2007; semantic distance in an analogy task, Green, Kraemer, Fugelsang, Gray, & Dunbar, 2010; increasingly difficult line length judgment, Grinband, Hirsch, & Ferrera, 2006). One study reported greater dmPFC activation in inductive rather than deductive reasoning (Goel, Gold, Kapur, & Houle, 1997). While this study did have references to mental states or


Author's personal copy INTRODUCTION TO SOCIAL COGNITIVE NEUROSCIENCE | Social Versus Nonsocial Reasoning

human agents in the stimulus material, this provides an unlikely explanation of dmPFC involvement, as the proportion was higher in the deductive condition. Based on these results, the dmPFC appears to serve a function that is not exclusively social, but nevertheless more typically involved in social-reasoning paradigms. In an attempt to shed light on the role of the dmPFC in social and nonsocial cognition, Baetens, Ma, Steen, and Van Overwalle (2013) recently reported within-participants activation overlap in the dmPFC for participants engaged in a trait inference task and a nonsocial object classification task. Participants viewed images depicting either a person engaged in everyday activities, or pictures of animals and objects. In the social condition, they had to generate the personality traits of the depicted person, and in the nonsocial condition, they had to generate the objective semantic categories to which the nonhuman object belonged. In both conditions, the description of the visual characteristics of the image served as a baseline. The social and the nonsocial condition both provoked stronger activation in the dmPFC compared to the visual description baseline, which showed a large overlap (as well as in other parts of the mentalizing system, such as the ventral mPFC and the precuneus, see Figure 2). Both the social and the nonsocial tasks were more abstract than the visual description task, in that they required participants to draw upon information that was not readily observable, especially knowledge represented in semantic memory. In other words, these tasks revolved around the meaning of the stimuli, rather than their perceptual properties. It is conceivable that the retrieval of meaning can explain the occurrence of dmPFC activation in the nonsocial reasoning tasks mentioned above (e.g., activation proportional to semantic distance in an analogy task, Green et al., 2010), and for the same reason, the dmPFC may be involved more often in social reasoning, which often requires seeking meaning beyond observable actions and features. This may also explain the patterns of results from within the social domain, including the positive correlation between dmPFC activation and the level of abstraction at which behavior is represented (e.g., ‘how is this person doing this?’ < ‘what is this person doing?’ < ‘why is this person doing this?’, Spunt & Lieberman, 2012; Spunt, Satpute, & Lieberman,

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2011). Furthermore, this proposal agrees with the specific sensitivity of the mentalizing system to unobservable characteristics, as described by Van Overwalle and Baetens (2009), as well as a large review on the semantic system that describes the mPFC as a core region involved in generating meaning (Binder, Desai, Graves, & Conant, 2009). A recent review, which stresses the importance of studying brain function in terms of large networks rather than discrete structures with discrete functions, situated the mPFC in the ‘conceptualization’ network (Barrett & Satpute, 2013), again in concordance with a domain-general function related to meaning retrieval. Yet, even though the mPFC is involved in a domain-general meaning-oriented function, this involvement does not preclude a centrally or primarily social role for the brain region. It is quite possible that this capacity primarily evolved to enable our social functioning, only later being recruited in nonsocial circumstances. The ability to handle unperceivable things such as betrayal, intention, or perspective must have been of tremendous importance, even in the most primitive social relations of our ancestors. For arguments against a similar line of thought regarding the social primacy of TPJ functioning see Mitchell (2008).

Concluding Remarks Social reasoning tends to involve a number of brain areas collectively known as the mentalizing network, although these regions seldom play important roles in nonsocial reasoning (Van Overwalle, 2011). The neural substrates supporting social and nonsocial reasoning, as typically implemented in contemporary research, are probably even antagonistically related (Jack et al., 2013). Nevertheless, under the right conditions, nonsocial reasoning may also rely on the so-called mentalizing network, suggesting that it is not exclusively involved in social reasoning. The TPJ activation often engaged in false belief reasoning may thus reflect a process of attention reallocation (i.e., disengaging from one’s own perspective to that of another, see Mitchell, 2008), and the mPFC may be critically involved in situations prompting a focus on the meaning of stimuli (see Baetens et al., 2013).

Figure 2 Overlap between social and nonsocial abstraction tasks. Red denotes stronger activation in a social trait inference task and a nonsocial semantic object classification task than in a matched visual description task. Blue denotes the inverse comparison. MNI coordinates 5, 30, 30. Adapted from Baetens K, Ma N, Steen J, and Van Overwalle F (2013) Involvement of the mentalizing network in social and non-social high construal. Social Cognitive and Affective Neuroscience http://dx.doi.org/10.1093/scan/nst048.


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How can we understand the often-observed differences between social and nonsocial reasoning? Social neuroscience’s origin in an appeal for multilevel analyses (Cacioppo & Berntson, 1992) might be of importance here. At the highest level of organization, social processes may simply be too complex for deductive, atomic, and propositional understanding. Indeed, vital pieces of social information are more often than not hidden from direct perception. Semantic knowledge or meaning, the conscious residue of our aggregate prior experience, may therefore be a crucial shortcut for reasoning about the social world, and the mentalizing system may be critically involved in handling it.

See also: INTRODUCTION TO COGNITIVE NEUROSCIENCE: Semantic Memory: Cognitive and Neuroanatomical Perspectives; Semantic Processing; INTRODUCTION TO SOCIAL COGNITIVE NEUROSCIENCE: Mentalizing; The Use of Brain Imaging to Investigate the Human Mirror Neuron System.

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