The brain has long enjoyed a privileged status as psychology’s favorite body organ. This is, of course, unsurprising given that the brain instantiates virtually all mental operations, from understanding language, to learning that fire is dangerous, to recalling the name of one’s kindergarten teacher, to categorizing fruits and vegetables, to predicting the future. Arguing for the importance of the brain in psychology is like arguing for the importance of money in economics.
More surprising, however, is the role of the entire body in psychology and the capacity for body parts inside and out to influence and regulate the most intimate operations of emotional and social life. The stomach’s gastric activity , for example, corresponds to how intensely people experience feelings such as happiness and disgust. The hands’ manipulation of objects that vary in temperature and texture influences judgments of how “warm” or “rough” people are. And the ovaries and testes’ production of progesterone and testosterone shapes behavior ranging from financial risk-taking to shopping preferences.
Psychology’s recognition of the body’s influence on the mind coincides with a recent focus on the role of the heart in our social psychology. It turns out that the heart is not only critical for survival, but also for how people related to one another. In particular, heart rate variability (HRV), variation in the heart’s beat-to-beat interval, plays a key role in social behaviors ranging from decision-making, regulating one’s emotions, coping with stress, and even academic engagement. Decreased HRV appears to be related to depression and autism and may be linked to thinking about information deliberately. Increased HRV, on the other hand, is associated with greater social skills such as recognizing other people’s emotions and helps people cope with socially stressful situations, such as thinking about giving a public speech or being evaluated by someone of another race. This diverse array of findings reflects a burgeoning interest across clinical psychology, neuroscience, social psychology, and developmental psychology in studying the role of the heart in social life.
A key moment for the field came in 1995, when Stephen Porges, currently a professor of psychiatry at the University of Illinois at Chicago, put forth Polyvagal Theory, a theory that emphasized the role of the heart in social behavior. The theory states that the vagus nerve, a nerve likely found only in mammals, provides input to the heart to guide behavior as complex as forming relationships with other people as well as disengaging from others. A distinguishing feature of Polyvagal theory is that it places importance not on heart rate per se, but rather on the variability of the heart rate, previously thought to be an uninteresting variable or mere noise.
Since 1995, a broad spectrum of research emerged in support of Polyvagal theory and has demonstrated the importance of the heart in social functioning. In 2001, Porges and his colleagues monitored infants when they engaged in a social interaction with the experimenter (cooing, talking, and smiling at them) and when they encountered the experimenter simply making a still face—a frozen expression—toward them. Infants’ HRV not only increased during the social interaction, but also increases in HRV predicted positive engagement (greater attention and active participation by the infants) during this interaction. In adults as well, HRV appears to be associated with success in regulating one’s emotions during social interaction, extraversion, and general positive mood.