One possibility is that social interactions involve qualitatively different processes than those perceptual, cognitive and motor computations that subserve the processing of information about the objective physical reality (Adolphs, 2010). Such a modular view of the mind (Fodor, 1983) would postulate that in the case of mental state attribution in social contexts, specific forms of knowledge and particular brain modules exists that serve these explicit social information processing functions. In cognitive neuroscience, it has been debated whether certain brain regions respond selectively to social stimuli, as in the case of faces, the fusiform-face area (FFA) (Kanwisher et al., 1997; Kanwisher, 2000) or in the case of body parts, the extrastriate body area (EBA; Downing et al., 2001). Similarly, it has been argued that the right temporal parietal junction (rTPJ) performs computations specifically related to the mental states of other individuals (Saxe and Kanwisher, 2003). Such domain-specifc views of the mind and brain has been criticised by advocates of a more distributed theory of mental processes in which information coding and processing emerges from the brain's dynamic and distributed organization in space and time (e.g., Haxby et al., 2000; Mitchell, 2008 in the field of social neuroscience).

The idea that an intersubjective epistemic perspective has to be added to the subjective first-person and the objective third-person perspective is by no means new. The basic idea can already be traced back to the beginning of the last century in the work of Heidegger (1927/1975, 1927/1986) and Mead (1925, 1926, 1934). More recent versions that use the metaphor of a “second-person perspective” can be found in Varela and Shear (1999); Bohman (2000); Davidson (2004); Habermas (2004); and Reddy (2008), for an overview see Lindemann (2006).

The idea has gained momentum in recent years with the advance of social neuroscience. Research in this area has resulted in an increasing demand for a clarification as to what kind of knowledge understanding other minds is, how this knowledge is acquired, and whether or not it can be separated from other kinds of knowledge acquisition.

This requires a closer investigation of how the notion of the “second-person” is currently utilized in the literature. Varela and Shear (1999) as well as Petitmengin (2006) introduced the term for an interview method by which subjective first-person experiences are gathered as “data” with the help of another “second” person. This approach, especially its underlying idea of the physical presence of a second-person, may have influenced other fields like developmental psychology (Reddy, 2008) and neuroscience (Schilbach, 2010; Schilbach et al., 2010a; Wilms et al., 2010). Still, there is unclear usage of a number of similar terms. For example, the confusing use of similar terms such as “second-person account,” “second-person engagements,” “second-person experiences” (Schilbach et al., in press), and “second-person perspective” demonstrate a lack of a common language. Here we will focus on the concept of second-person perspective, as it seems to be essential in social cognition.

One crucial question in defining second-person perspective is whether social interaction with a verbatim second-person plays a decisive role. This seems, for example, to be Schilbach's (2010) view. He postulates, “social cognition is fundamentally different when an individual is actively and directly interacting with others. In such cases, an individual adopts a “second-person perspective” in which interaction with the other can be thought of as essential or even constitutive for social cognition, rather than merely observing others and relying on a “first- (or third-) person grasp” of their mental states.” (p. 1).

Wilms et al. (2010) use the term “online interaction” instead of “online social cognition.” Assumingly, what they wish to express is social cognition which is in place during real-life interaction. Moreover, they use this as a synonym for second-person perspective taking: “‘Online’ interaction crucially involves […] establishing reciprocal relations where actions feed directly into the communication loop […]. This has been referred to as adopting a “second-person-perspective” […] which can be taken to suggest that awareness of mental states results from being psychologically engaged with someone and being an active participant of reciprocal interaction thereby establishing a subject-subject (“Me-You”) rather than a subject-object (“Me-She/He”) relationship.” (p. 1).

Others (De Jaegher et al., 2010) define social cognition without any reference to the second-person perspective. Although stressing the relevance of a comparatively strong version of interaction for the development of social cognition, De Jaegher et al. (2010) concede that social cognition may occur in the absence of interaction, e.g., in remote observation of social scenes.

With these observations in mind, we can start to characterize social cognition as the acquisition of knowledge² about other persons' mental states, i.e., their beliefs, desires, and intentions and also insight about the meaning of their utterings. It would follow that social cognition includes at least two essential features that should be accounted for with any definition. First, social cognition is a means of knowledge acquisition. We suggest that this aspect can be specified by referring to the distinction between the second-person perspective, on the one hand, and the first- and third-person perspective on the other. Second, social cognition occurs in social contexts. One way to specify this aspect is to ask whether or not the subjects involved interact, i.e., whether they are engaged in online or offline social cognition. Taking interaction as a reciprocal pattern of action and reaction³ between at least two agents affecting each other, we assume that knowledge about other persons can be acquired without interacting with them, for example, when one reads a letter or watches a movie describing another person's mental states. Consequently, we argue that second-person perspective taking can happen without direct interaction and that this perspective is, therefore, not synonymous with being engaged in interaction or online social cognition. Rather, treating interaction and perspective taking as two different aspects of social cognition results in a much more differentiated and suitable view.

Perspectives, in a nutshell, are ways of acquiring knowledge (for more details see Pauen, 2012). Perspectival distinctions answer questions like: (1) “What is this knowledge about?” and (2) “How do we acquire this knowledge?” First-person perspective taking provides self-knowledge. So, reflecting on the questions posed above, first-person knowledge (1) is about the subject's own mental states and (2) is acquired directly via those very mental states that are directly accessible only for the subject him or herself. It can, thus be characterized as subjective because it is acquired by and is about the subject's own mental states (Pauen, 2010). Third-person knowledge, by contrast, (1) is about all kinds of objective (and mostly external) facts, both scientific and non-scientific and (2) it is acquired by all kinds of objective evidence that is accessible to everyone, among them external observation and scientific methods. As a consequence, the third-person perspective can be characterized as “objective.”

But why is it necessary to add a second-person perspective to the first- and third-person perspective to begin with? In order to see this, imagine that you are locating a restaurant in an unfamiliar city. In this endeavor the third-person perspective is helpful because the eatery has a definite location in space that can be assessed by consulting a map. By contrast, you apply the first-person perspective when you wonder whether it is worth stopping for a pretzel to slake your hunger before completing the journey: Are you really that hungry? But when you reach your destination a quarter of an hour late because of this detour, and being full yourself, you need to find out how your companion feels. Is she still hungry? Is she angry because you are late? Or would she like to go to another place? In assessing our companion's state the first-person perspective provides no information because, unless they also stopped for dinner, their mental state is different to our own. Likewise, the third-person perspective cannot be of assistance because there are no objective facts upon which to assess the person's thoughts and feelings.

Thus, our capacity to infer our companions feelings is a paradigmatic case of social cognition which is set apart both from third- and first-person perspective taking by at least two distinctive features. First, unlike first-person perspective taking, it is not about one's own mental states. Second, unlike the third-person perspective, it is not just about facts. Rather, social cognition is a question regarding another person's mental states; i.e., it is about what our companion thinks, what she feels, and what her intentions are.

But how does social cognition relate to our capacity to acquire knowledge? Social cognition is neither about pure objective data as in third-person perspective taking, nor is it the application of our subjective mental states, as in first-person perspective taking. Instead, social cognition is a means of knowledge acquisition that involves a combination of both. Just as in first-person perspective taking, we draw on our own feelings and experiences during social cognition in order to access the other person's feelings and experiences. Likewise, social cognition is like third-person perspective taking when we draw on our general background knowledge as well as on the person's behavior, gestures, and facial play to understand why they are acting as they are. It is clear that knowledge that we gain by taking the second-person perspective is neither purely objective nor subjective; it is intersubjective because it requires that we understand the other as a person with their own thoughts, feelings, and experiences⁴. In other words, the second-person perspective is set apart from the first- and the third-person perspective both in terms of its relation to (1) knowledge content and (2) knowledge acquisition (Pauen, 2012).

Note however, that in current papers, we find a quite heterogeneous usage of the terms. Mojzisch et al. (2006, see p. 185) as well as Schilbach et al. (2006, see p. 718) speak of on- vs. offline Theory of Mind (ToM). Wilms et al. (2010) refer sometimes to on- vs. offline mentalizing (p. 1), and sometimes to on- vs. offline social cognition (p. 8). While social cognition is, however, generally used as an umbrella term for all socially relevant processes and thus includes also action intention understanding, affective resonance and empathy, face recognition, social memory, and many others, mentalizing is usually reserved to specifically denote cognitive perspective taking processes and the underlying ToM network. Therefore, we prefer to use the term of on- or offline social cognition in the context of the present paper.

Each of these abilities is associated with different brain circuits. Early research on the discovery of the mirror neurons in macaque monkeys (di Pellegrino et al., 1992; Gallese et al., 1996; Rizzolatti et al., 1996; for a review see Rizzolatti and Fabbri-Destro, 2010) suggested that the same cells, which are activated when a monkey is performing a particular grasp, also fire if the same monkey merely observes another during the same action. Later research in humans, mostly using fMRI, demonstrated “shared networks” between self-performed and vicariously perceived actions activate similar regions in the human brain. The identified neural network comprised the inferior parietal lobule (IPL), the ventral premotor cortex, and the caudal part of the inferior frontal gyrus (IFG) (Dinstein et al., 2007; Gazzola et al., 2007; Etzel et al., 2008, for reviews see Blakemore and Decety, 2001; Grèzes and Decety, 2001).

This research was subsequently expanded to the domain of emotions and empathy (Gallese and Goldman, 1998; Gallese, 2001; Preston and de Waal, 2002) culminating in the emergence of empathy research in the field of social neuroscience (for reviews see Decety and Jackson, 2004; de Vignemont and Singer, 2006; Keysers and Gazzola, 2006, 2009; Singer and Lamm, 2009). A multitude of imaging experiments in humans in the domain of empathy for pain, disgust, taste, and touch revealed that, in contrast to mirror neuron networks, in the domain of motor actions, sharing sensations and feelings with others engages somatosensory cortices, as well as anterior parts of the insula and anterior cingulate cortex (ACC; Keysers et al., 2010; Fan et al., 2011; Lamm et al., 2011). In addition to this affective route, researchers have distinguished a cognitive route which is helpful for understanding the beliefs, thoughts, and desires of other people. This “mentalizing,” “ToM”, or “cognitive perspective taking” (Premack and Woodruff, 1978; Wimmer and Perner, 1983; Frith and Frith, 1999, 2003; Baron-Cohen et al., 2000) network typically comprises areas in the medial prefrontal cortex (mPFC), precuneus, superior temporal sulcus (STS), and rTPJ (for reviews see Frith and Frith, 1999, 2003; Gallagher and Frith, 2003; Saxe et al., 2004; Amodio and Frith, 2006; Saxe, 2006; Mitchell, 2009).

Many of these neural systems are also recruited when individuals are not interacting in a social context. For example, the mPFC is activated by tasks involving the evaluation of the personality of the self and others (Kelley et al., 2002; Macrae et al., 2004; Mitchell et al., 2006), as well as by the task of assessing the likelihood of enjoyment of activities that will occur in the future (Tamir and Mitchell, 2011). Likewise, regions including the TPJ, the mPFC, and the PCC are recruited when thinking becomes decoupled from the events in the here and now and stimulus independent mental contents form the cornerstone for consciousness (Mason et al., 2007; Christoff et al., 2009; Smallwood et al., 2011; Stawarzyck et al., 2011). Taken together, the fact that similar neural processes are engaged during self-referential processes and social interactions, as well as internally generated thoughts with no explicit external referent, suggests that many forms of social cognition are likely to be involved in a more general set of processes that allow the mind to devote processing resources to make predictions necessary for navigation through social life (Frith, 2007).

What does it take for an action to be real social interaction? The experimental aim in social neuroscience, following Wilms et al. (2010 who, in turn, follow Frith, 2007) consists in “closing the loop between interaction partners” (p. 1). This means that the action of one subject (henceforth A) should trigger a response of her partner, a sentient being (henceforth B), which in turn influences A and A's reaction. This particular feedback has a specific effect on B resulting in a reaction in B that subsequently changes A's mental state and so on (see Figure ​Figure1,1, left panel). In every iteration, each partner's mental state is changed by his/her partner and these new states form the basis of the next iteration of social interaction. One basic feature of such a reciprocal interaction is the occurrence of emergent qualities, i.e., the largely unpredictable rearrangement of the already existing entities, namely A and B's possible reactions. Such emergence is only possible if none of the involved subjects responses are controlled. Without the essential unpredictability that occurs in natural social interaction reciprocal changes in behavior would not occur. Along these lines Schippers et al. (2010) stated that it is, therefore, difficult to assess when one action ends and another starts (p. 9388; please note that for this reason, the time of measurement in the left panel of Figure ​Figure11 should be seen as no more than a formal orientation). It is only when the design of the experiment allows for an action possessing four specific criteria (dynamic interplay, a virtually unlimited range of responses, living and uncontrolled partners, and emergent qualities) that we can speak of real social interaction.

Just consider an example of a fundamentally social form of behavior such as tickling. Blakemore et al. (1998) have argued that tickling, certainly a low-level, bottom-up, mostly pre-reflective phenomenon is quintessentially social because, at least under normal conditions, the sensation can only arise when another individual delivers the touch. It has been proposed that the reason we cannot tickle ourselves is that during self-generated movements the brain produces a forward model that allows us to predict the effects of tickling and thus cancel these effects out in advance. When the touch is delivered by another, this model is absent, making the touch unpredictable that, hence, leads to the sensation of being tickled (Blakemore et al., 1998, 2000).

In contrast, the right panel in Figure ​Figure11 illustrates other ways of modeling social interaction, which are relevant in the context of present social neuroscience research. In these types of social interaction, A's behavior is studied under the full control of B's response (in experimental research, the presence of the subject's interaction partner B is often feigned and therefore entirely controlled by the experimenter). Strictly speaking, because A's behavior does not cause a novel and unpredictable response in B, it is similar to a blind alley. B, being just an algorithm, would always react independent of A's action. This is indicated by the dotted lines in the right panel of Figure ​Figure11.

Although A repeatedly reacts to fixed “actions” made by B, the model that guides B's behavior does not change over time and so there is “no closing of the loop.” Accordingly, the emergent qualities of such interactions are limited; hence, no reciprocal transformation can happen from T1 until T4. While temporally dynamic, such controlled interchanges are no more than “pseudo social interaction.”

Among other research questions, one focus of these studies was to examine whether brain responses of subjects differ as a function of whether they believe that they are interacting with a real human partner or simply with a computer or a non-intentional playing partner (e.g., McCabe et al., 2001; Gallagher et al., 2002; Singer et al., 2004b). McCabe et al. (2001) were among the first to conduct experiments on playing a two-person game in the scanner. The subjects played either with another alleged person or a computer and were asked to make choices in the game tree. They all cooperated less in the condition under which they thought that they were playing with an algorithm. Moreover, the mere belief that they were playing with a human being resulted in the activation of specific regions of the prefrontal cortex.

Gallagher et al. (2002) introduced the “stone-paper-scissors” game in a PET paradigm. Their goal was to “investigate the neural substrates of ‘on-line’ mentalizing” (p. 814). Again, the subjects believed that they were either playing with another person (whom they met shortly before) or a computer, while in fact all responses were constantly generated by a computer program. As the respective neural substrate of the alleged social encounter, Gallagher et al. (2002) recorded activity in the anterior portion of paracingulate cortex bilaterally.

Similarly, Sanfey et al. (2003) scanned subjects playing the Ultimatum Game (UG) who had to respond to fair as well as unfair offers. Unfair offers elicited anger and rejection in the participants when another person to whom they had been introduced beforehand made them but not when these unfair offers were made by a computer. In the case of the illusion of interacting with a conspecific, the anterior insulae, the dorsolateral prefrontal cortex, and the ACC showed higher activation.

Rilling et al. (2004) tried to create a paradigm that allowed for the “immersion of participants in real social interaction that have personally meaningful consequences” (p. 1694) by scanning subjects while playing the UG and the Prisoner's Dilemma Game (PDG) using both, assumed human and computer partners, outside the scanner. These studies demonstrated that these tasks only activated the ToM network (including the anterior paracingulate cortex, the posterior, and mid-STS, as well as the hippocampus and regions of the hypothalamus) when the subjects believed that they were playing with real human beings. Just like in the studies conducted by Gallagher et al. (2002) and Sanfey et al. (2003), the illusion that a real partner B was present elicited different brain patterns than if the partner was assumed to be artificial.

Finally, Singer et al. (2004b) involved participants in sequential trust games with intentional or non-intentional playing partners and revealed, in line with the findings above, that only when subjects believed to play with intentional agents, emotion-related brain activation (e.g., in the left amygdala, the insulae, and reward-related areas) were induced when perceiving intentional co-operator or defector faces as compared to neutral players.

Another set of paradigms focused on measuring the effects of directed or averted gaze on neural processes. For example, in an early PET study, Wicker and colleagues (1998) investigated the neural activation of mutual gaze (“a psychological process during which two persons have the feeling of a brief link between their two minds”, p. 221). Subjects were shown videos of persons looking toward them (in a mutual gaze condition) or away (in an averted gaze condition). This study revealed that eye contact activates the occipital part of the fusiform gyrus, the right parietal lobule, the right inferior temporal gyrus, and the middle temporal gyrus in both hemispheres. Further effects of eye contact were presented by Kampe et al. (2001) who demonstrated that the perceived attractiveness of an unfamiliar face depicted on still photographs augmented activity in the ventral striatum when the viewer met the person's gaze, whereas it decreased in the absence of direct eye contact. Central reward-related brain areas seem, thus, to be engaged during direct but not averted gaze when presented with still pictures of human faces.

In more recent eye-gaze paradigms, Schilbach et al. (2006, 2010a,b) sought to characterize neural correlates of being personally involved in social interaction by introducing more dynamic virtual-reality technologies in the scanner environment. Virtual characters were created that gazed at and greeted others—either the subjects (who were lying passively in the scanner) or a bystander. One of their main neuroscientific findings was that the vMPFC underlies the perception of social communication and feeling of personal involvement (Schilbach et al., 2006). Moreover, when the sharing of attention with the avatar was self-initiated by the participants, this led to an increase of neural activity in the ventral striatum (Schilbach et al., 2010a). Similarly, Wilms et al. (2010) tried to study social encounters in a truly interactive manner. They asked subjects in the scanner to respond or to probe the gaze of another person, depicted as an anthropomorphic avatar (who was actually computer-operated). The subject's goal was to establish eye contact with the avatar and to jointly attend to one of three objects on a screen as a function of the subject's eye-gaze. This method of interactive eye-tracking reflects the attempt to close the interaction loop between A and B. More precisely, Wilms et al. (2010) were interested in the neural differences of successfully initiating joint attention compared to mere gaze following. In this regard, they reported a main effect of joint attention that resulted in the activation of the mPFC, PCC, and the anterior temporal poles.

Another type of social neuroscience paradigms involves the presence of real people present in the scanner environment. For example in empathy for pain research, subjects in the scanner were coupled with either their loved ones (Singer et al., 2004a) or unfamiliar persons who differed in important aspects such as perceived fairness or group membership (Singer et al., 2006; Hein et al., 2010) who sat outside of the scanner room but visible to the subjects. In these paradigms, brain responses are elicited by creating the experience of painful shocks in the subjects. This first-personal pain response is compared with those brain responses elicited when watching the real person present in the same room suffering from pain.

Finally, some recent innovative paradigms have started to use cross-correlational statistics to compare brain activity of two individuals involved in a task together (Schippers et al., 2010; Anders et al., 2011). For example, Schippers et al. (2010) asked couples of participants to play charades in the scanner in order to examine brain activity during longer streams of social communication. Both of their brains were measured at separate times in the same scanner (thus, the authors did not draw on hyper-scanning technology). In one session, brain activity was recorded during the gesturing of a word for the partner. This gesturing was videotaped so that their partners could guess it in the subsequent scanning session. Results show that during guessing, the subject's brain activity in the putative MNS and the vmPFC is caused by fluctuations in activity in the pMNS of the gesturing partner.

All the above-mentioned studies have been conducted with imaging methods. What about EEG-studies investigating social processes? Lindenberger et al. (2009) investigated interbrain synchronization when eight pairs of guitar players performed a short piece together. They found significant between-brain oscillatory couplings during the preparatory period of metronome tempo setting in especially the fronto-central connections in the frequency range between 2 and 10 Hz, as well as after the play onset in the frequency range between 0.5 and 7.5 Hz. According to the authors, this coupling can be interpreted as a sign for social attunement.

Similarly, the paradigms created by Schilbach and colleagues do not constitute real social interaction because even though B reacts to A's behavior, B's response is programmed by the experimenter and so lacks the unpredictability of a real person. Despite its novelty relative to the previous social neuroscience paradigms, the use of still pictures of faces as outlined above offers no emergent qualities of real interaction. Schippers et al. (2010) presented a different and ambitious approach to the “information flow across brains during social interactions” (p. 9391). Nevertheless, each trial of guessing the action ended without the other's spontaneous feedback, and the subjects gestured the word-to-be-guessed in a video camera instead of directly toward the partner's face, therefore we can conclude that, although this experiment captures naturalistic complex symbolic and non-verbal behavior, the “loop” was never fully closed within a single interaction. The sought-after information flow from one brain to another was not really flowing.

Finally, the empathy paradigms (Singer et al., 2004a, 2006; Hein et al., 2010), even though integrating authentic unconstrained (and uncontrolled) partners in the same scanner environment, can again not be considered as real social interaction paradigms, as the response of B is not important for the analyses or claims of this investigation. The only thing that matters is the brain response of A.

Do the EEG-studies capture real social interaction? Although Lindenberger et al. (2009) studied coordinated action, this again do not fulfill our criteria of studying real social interaction. The guitar players follow a common goal (performing a specific piece together over 60 trials), preventing opportunities for creative actions and responses. For real musical interaction to be studied, it would be necessary to record the brain activities while two individuals, for example, improvise. Imagine for example jazz improvisation, where the tunes emerges through the reciprocal impact that one players melody has on the other player's tune and by doing so capture real elements of social interaction. During improvisation, repetition, and predictable responses are nearly impossible because each individual's contribution emerges from the process of listening and replying to the other (Seddon, 2005). An additional worry concerning these studies is that observed between-brain oscillation can also be explained by the fact that the musicians are merely following the same synchronizing stimulus (i.e., the metronom or the melody they play). This would then again not be an example of real social interaction but similar to two persons watching the same movie, and whose brain activities consequently are synchronized by this same visual material.

Also, in Kourtis et al.'s (2010) EEG-study two persons “interact,” but only in the sense that they pass each other an object. Although this counts as interaction because the subjects are real living persons who can act jointly in a face-to-face setting, the paradigm restricted the type of interaction that was possible and so the two minds do not mutually shape each other by the unpredictability of their responses. Due to the limited range of behavior and the restricted possibility for emergent qualities, we do not see the closing of the loop here, neither.

A closer look into the brain areas involved in the social neuroscience experiments reviewed suggest that the answer to both questions is no. To answer question (a), the social brain is not exclusively social; rather, each of these brain regions has been shown to also be involved in other non-social tasks. For example, even though “the meeting of minds” (Amodio and Frith, 2006) certainly has hedonic qualities and may “feel good” (see Schilbach et al., 2010a), the ventral striatum or other reward-related brain areas cannot be seen as specific neural correlates of the second-person perspective or of mutual social interaction because these brain areas are known to be sensitive to all kinds of rewards, be it social or non-social (e.g., Schultz, 2002; O'Doherty et al., 2006). Hence, these regions will also be equally strongly involved in pleasant non-social activities such as indulging in a glass of high-class Bordeaux. Similarly, the consistent involvement of anterior insula and mACC in empathy for pain paradigms (see Lamm et al., 2011) does not make these brain regions specific “empathy regions.” On the contrary, these “shared activation” studies reveal that these regions are also involved in processing negative affective experiences in the self or in other non-social context (see also Singer, 2012).

The phenomenon of ticklishness when being tickled by others but not by oneself, as mentioned earlier, can be taken as a good example to discuss the question to whether a specific neural system is responsible for social interaction. This phenomenon does not occur because of unique neural computations specialized for being tickled but rather emerges from more general predictive properties of our sensory and motor system and the fact that we can predict the effects of our own actions but not those of others⁵. Accordingly, online social cognition could be explained by understanding how different basic cognitive, emotional, and motor processes and their underlying brain mechanisms cooperate to produce representations of the actions, sensations, or mental state of another individual. Hence, a review of the present social neuroscience literature does not support the claim that neural processes or computations that specifically subserve the processing of social stimuli exist. In sum, the answer to question (a) would be that to the best of our knowledge so far, no neural computations or neuronal networks specifically dedicated to social stimuli or social cognition alone have been identified.

Would this conclusion have to change if eventually neuroscientists succeed in bringing real social interactions into neuroscience paradigms? The hope of identifying neuronal networks, neural computations, or even single cells, that would selectively only react when we are involved in online social cognition, seems—given the hitherto existing neuroscientific evidence—simply highly unlikely. For this to be the case, our brains would need to contain cells or perform computations that are only sensitive to the interactive nature of two intentional living agents but are silent when merely one agent is concerned, even if this involves the processing of social stimuli. Following this line of reasoning, the answer to question (b) would again have to be no.

Having said this, we would, however, expect that social interaction might activate neuronal patterns (but not hitherto unknown areas) different from situations where subjects are not personally being involved. Still, this effect would come as no surprise, as it may just stem from mere attention and saliency effects known to modulate activation patterns in the brain. The brains of subjects being half asleep will obviously show a different activation pattern than a highly engaged subject irrespective of whether this subject is engaged in social or non-social information processing.

Note also, that even though we have argued that social neuroscience has not yet succeeded in implementing real social interaction paradigms, the so-called social brain circuitries have nevertheless been discovered and repeatedly described on the basis of subjects merely believing in the presence of another interaction partner.

Even though the implementation of real social interaction paradigms may not reveal novel brain mechanisms exclusively devoted to social cognition or social interaction, it is important to stress at this point that the implementation of real-life social interactive paradigms can, nonetheless, inform our understanding of social dynamics and the psychological phenomena that emerge in these conditions. Social interaction is a central and enormously important factor for human evolution, ontogeny, and daily life, for example, in the development of individual personhood or self-consciousness. In evolutionary terms, for example, it has been argued that the demands of interacting with group members have been a vital and a powerful influence on the size of the neo-cortex of the brain (as measured by the ratio between the volume of medulla oblongata and neocortex Dunbar, 1998). According to this social brain hypothesis, the need to understand other minds, as well as the related processes of communication and self-control, drove an increase in neo-cortical volumes in mammals, particularly in primates. Social environments are also important at an ontogenetic level. Anecdotal evidence from the eighteenth century indicates that isolation from the social group, such as that experienced by feral children like the Wildboy of Averyon, leads to problems with developing more than rudimentary skills essential for social interaction (Zingg, 1940). More recent studies showed that human psychosocial development is largely influenced by the quality of parent-child interactions (Beebe et al., 2008). Furthermore, developmental psychologists have stated that it is through interactive sharing that children ontogenetically acquire the capacity of taking and confronting intersubjective perspectives, i.e., understanding other minds (Moll and Meltzoff, 2011). We argue that face-to-face encounters are a necessary condition for social cognitive abilities to evolve, but that, once in place, other minds can also be understood when the persons are not engaging in real social interaction. Therefore, we have challenged the currently widespread narrow definition of second-perspective taking. In sum, at both the level of evolution and of ontogeny, immersion in a complex social environment seems necessary for the human mind to develop normally.