From Mind Perception to Mental Connection: Synchrony as a Mechanism for Social Understanding

Connecting deeply with another mind is as enigmatic as it is fulfilling. Why people ‘‘click’’ with some people but not others is one of the great unsolved mysteries of science. However, researchers from psychology and neuroscience are converging on a likely physiological basis for connection – neural synchrony (entrainment). Here, we review research on the necessary precursors for interpersonal synchrony: the ability to detect a mind and resonate with its outputs. Further, We describe potential mechanisms for the development of synchrony between two minds. We then consider recent neuroimaging and behavioral evidence for the adaptive benefits of synchrony, including neural efficiency and the release of a reward signal that promotes future social interaction. In nature, neural synchrony yields behavioral synchrony. Humans use behavioral synchrony to promote neural synchrony, and thus, social bonding. This reverse-engineering of social connection is an important innovation likely underlying this distinctively human capacity to create large-scale social coordination and cohesion. At different states in our lives, the signs of love may vary: dependence, attraction, contentment, worry, loyalty, grief, but at the heart, the source is always the same. Human beings have the rare capacity to connect with each other, against all odds. Michael Dorris People seek meaning in life through the company of others. Yet, as anyone who has ever felt lonely in a crowd can attest, company alone is not enough. What people really seek is connection, the pleasurable mutual engagement between oneself and another mind. However, despite its importance, the origin of mental connection is one of the greatest unsolved mysteries of science. Here we review studies from a diverse literature that, collectively, converge on an origin of mental connection. First, we review evidence that the perceptual systems in the human brain are tuned to seek other minds and predict their behavior. Second, we suggest that the ability to dynamically predict behavior affords synchrony. We highlight the importance of synchrony as an adaptive neural mechanism by which people entrain to others; an adaptation that blurs the self-other boundary and promotes social bonds through the pleasurable feeling of connection. Finally, we speculate that the human brain, in contrast to the brains of other species, is uniquely able to reverse engineer connectionby-synchrony, thereby creating mass social coordination and cohesion. How the Brain Finds a Mind As Piaget famously opined, cognitive development is about making models. As children develop, their models of the world become increasingly sophisticated via the shaping Social and Personality Psychology Compass 6/8 (2012): 589–606, 10.1111/j.1751-9004.2012.00450.x a 2012 Blackwell Publishing Ltd processes of assimilation and accommodation (Piaget, 1954). Perhaps the earliest model the human brain develops is that of another being. From birth, humans are predisposed to attend to animate beings. Newborns look more at faces than any other objects (Johnson, Dziurawiec, Ellis, & Morton, 1991), listen longer to human voices than other sounds (Vouloumanos & Werker, 2007), and gaze longer at upright versus upside-down displays of biological motion (Simion, Regolin, & Bulf, 2008). Since babies lack knowledge about the world, this initial interest is almost certainly driven by simple percepts. Indeed, two dots and a line are enough to capture an infant’s attention, but only when presented in the configuration of a face: two dots for eyes, and a line for nose (Goren, Sarty, & Wu, 1975). This pattern-matching predisposition quickly develops into an increasingly sophisticated set of criteria for what qualifies as an animate being. The brain subjects faces, motion, and voices to a demanding array of tests designed to scrutinize input for evidence of a mind worthy of additional cognitive resources (e.g., action prediction, empathy). The brain’s Turing Tests Alan Turing, a mathematician and computer scientist, famously outlined a scenario that would define whether a computer could be said to ‘‘think.’’ In this scenario, a person asks a series of spontaneous questions, and a second person or a computer responds to these questions via text. A computer passes the ‘‘Turing Test’’ if a human judge confuses its text responses with that of a real person. Today, computer programs can pass the Turing Test, albeit briefly. Indeed, Artificial Conversational Entities, or ‘‘chatterbots,’’ initiate thousands of ‘‘chats’’ daily with unsuspecting Internet users who believe they are conversing with other human beings. By mimicking the behavioral characteristics of natural conversation, these chatterbots trigger the inference of another mind. It is one thing to fool someone into believing that computer-generated text originated from a live source. The brain, after all, did not evolve to process the veracity of text message authorship. Fooling the brain’s perceptual systems is a taller order. The human brain employs several perceptual Turing Tests devoted to scrutinizing faces, movements, and voices for evidence of minds worth modeling. The facial Turing Test: it looks like it has a mind It is hard to overstate the importance of the face as a social stimulus. Faces identify people, display mental states, and are evaluated along a host of dimensions (e.g., attractiveness, maturity, trustworthiness). Faces are important for the very reason that their root word suggests: they serve as the façades of other minds. Commensurate with this importance, faces capture attention faster than other objects (Langton, Law, Burton, & Schweinberger, 2008) and evoke a specific and rapid electrocortical response (Bentin, Allison, Puce, Perez, & McCarthy, 1996; Bentin et al., 2007; Watanabe, Kakigi, & Puce, 2003; Rossion & Jacques, 2008; cf. Gauthier, Curran, Curby, & Collins, 2003). This response is evoked by faces of all shapes and sizes, including schematic line drawings (Bentin et al., 1996; Gauthier et al., 2003; Rossion & Jacques, 2008; Watanabe et al., 2003). This broad response profile suggests that there is a rapid pattern-matching mechanism that flags input as a potential face (Jacques & Rossion, 2010; Sagiv & Bentin, 2001). This liberal detection mechanism is the reason people see faces in clouds, car grills, parking meters, and even the image of the Virgin Mary in a grilled cheese sandwich (Bloom, 2005). 590 Mind Perception and Mental Connection a 2012 Blackwell Publishing Ltd Social and Personality Psychology Compass 6/8 (2012): 589–606, 10.1111/j.1751-9004.2012.00450.x Detecting a face is important for the inference of mind, but a quick jaunt to the local mall reveals that face detection alone cannot be the whole story. Mannequins have faces. Dolls, avatars, masks, sculptures and most paintings in the National Gallery have faces. How do we cope with these face-wearing imposters? How do we know that these faces are not worthy of our mental models? Part of the answer is obvious: mindless faces are typically motionless. However, people can tell whether a face has a mind just by looking at a photograph. Therefore, there must be cues available in a single image that affords the discrimination of mind. This ability was recently investigated by Wheatley, Weinberg, Looser, Moran, and Hajcak (2011), who recorded electrocortical responses while participants viewed images of human faces and object faces (e.g., mannequins and dolls). The rapid, face-specific waveform described above was evoked by all faces regardless of whether they were animate or inanimate. However, only the human faces evoked a later sustained waveform with a latency of 400 ms (see Figure 1). This suggests that a second level of scrutiny is applied to faces post-detection. While all faces capture attention; only faces with minds sustain attention. Further evidence of this claim was found using artificially created animacy continua. To create these stimuli, photographs of human faces were morphed in image space with well-matched inanimate object faces (e.g., statues, dolls). Participants were asked to simply split an ordered row of faces (e.g., Figure 2) at the point where the face first appeared to ‘‘have a mind.’’ Across studies, people identified the same tipping point, an image around 65% human and 35% doll (Looser & Wheatley, 2010). It is at this point along the morph that faces first seem to have a mind attached.