Why Do We Experience Chills?

A few years ago, I proposed that the feeling of cold in one’s spine, while for example watching a film or listening to music, corresponds to an event when our vital need for cognition is satisfied. Similarly, I have shown that chills are not solely related to music or film but also to the practice of science (mainly physics and mathematics) and to the social logic of religious rituals. I believe that chills and aesthetic emotions in general can teach us something that we do not know yet. They can help us to understand what truly matters to the mind and to the society of minds.

When cold or sick, humans shiver. Shivering is a muscle tremor that produces heat which allows the body to maintain its core temperature in a changing world. Human core temperature can vary temporarily between about 28 to 42 degrees Celsius. Outside these thresholds, death occurs. Humans also shiver in the case of a fever, as heat slows down the rate of pathogen growth and improves the immune response of a living body. Goosebumps or piloerection (the bristling of hairs) can be side effects, as the muscle tremor causes hair to become erect which creates a thin layer of air, thus minimizing heat loss. Strangely enough, humans also shiver independently of any such events. For instance, certain social situations seem to provoke shivers.

Humans are particularly prone to shiver when a group does or thinks the same thing at the same time. When a crowd is sharing a common goal. When they listen to a national anthem or witness self-sacrifice. When they die for their ideas. When collective thought becomes more important than individual life. But humans also shiver from situations that are not social in nature. Some shiver when they manage to find a solution to certain mathematical problems for example, and so shivering cannot be reduced to a social mechanism.

Now, why does a psychological event trigger a physiological response related to the regulation of temperature? At a fundamental level, cognition requires change. If you stabilize a retina using adequate instruments, the organ ceases to transmit signals to the primary visual cortex, and one gradually becomes blind. From the standpoint of the sense organ, the same object never appears similar to itself twice. Two chairs are never exactly the same. In other words, one is constantly discovering a visual field. Everything you feel, you feel for the first time. Perception is really exploration and, if we can perceive anything at all, it is because we are constantly matching incoming sensory signals to available mental models. You rarely fail to recognize objects in your surroundings. The world is always already meaningful, and it is sometimes beautiful.

The process by which a mind adapts to its world is so effective that people constantly mistake one for the other. When a large part of thought matches a large part of the world, one might consciously feel what we call aesthetic emotions. Historically, aesthetics is the science of how perception meets cognition, the science of how you know what you see. The majority of aesthetic emotions are unconscious. They occur every time you see something. When you see something important enough, you might experience these emotions consciously. This happens through bodily changes such as tears, heartbeat increase, sweat – or shivers. The strange thing with shivering is that humans seem to shiver both when they are perfectly capable of predicting the behavior of external objects in real-time when it all fits together so well, and, surprisingly, when nothing at all can be predicted, when the situation goes out of control.

I propose that psychogenic shivers correspond to an event where the measure of the total similarity between all sensory signals and available mental models reaches a local peak value.

I propose that psychogenic shivers correspond to an event where the measure of the total similarity between all sensory signals and available mental models reaches a local peak value. This can be expressed mathematically in terms of the rate of change of a function of conditional similarity. In this context, any change in learning corresponds to an aesthetic emotion. When the function reaches a local maximum, its derivative tends toward zero, and learning slows down. This corresponds to a ‘turning’ point in your total knowledge. Ten years ago, Perlovsky predicted that such an event should involve knowledge about other minds and about the meaning of life.

We know that psychogenic shivers can be inhibited by an excitant, the opioid-antagonist naloxone. Naloxone is what you would inject in a clinical setting to a patient who is victim of an overdose; it is the antagonist of morphine. It does not come as a surprise that most of my subjects state that they relax after they experience an aesthetic shiver. Besides a clear analogy with the sexual drive, what does this tell us about the exploratory drive?

I argue that stories that provoke the shivers might bring about this relief of tension by allowing humans to overcome conflicts among fundamental parts of the mind. Such stories might help us to deal with internal contradictions, where both elements are equally resistant to change. Leon Festinger, who in 1957 invented the theory of cognitive dissonance, named this a dissonance of maximum amplitude. The mind creates stories to overcome its own contradictions. Anthropologists call this a myth, and we know from a wealth of work in anthropology that rituals are likely to provoke shivers down the spine.

We give two examples for such fundamental conflicts; one is biological and the other cultural. The biological conflict derives from the fact that, while we survive as a species by sharing goals, we might never access the goal of other minds directly. We thus shiver in cases of seemingly total communication – theoretical synchrony. Another example derives from the fundamental discordance between the altruistic nature of the human animal on the one hand, and the logic of the currently dominant social system on the other. These hypotheses would explain why you might shiver in the course of a film when empathy becomes a necessary condition to reduce narrative tension to its minimum. When the bad guy ends up saving the good guy.

There are three plausible explanations for the fundamental relation between cognition and temperature. One is physiological, the other is physical, and the third is biological. The physiological explanation simply consists of describing psychogenic shivers as a case of fever. The relation between emotion and temperature is in fact very ancient, and even reptiles display evidence of stress-induced hyperthermia.

The physical explanation relates the dissipation of heat at the shiver to the processing of information in the brain. In 1961 the physicist Rolf Landauer at IBM proposed the principle that any erasure of information should be accompanied by the dissipation of heat. This was verified experimentally a few years ago in Lyon. If this hypothesis is not entirely false, then we should eventually be able to predict the amount of heat produced, given accurate knowledge of the information process. Until then, I do not see any good reason to quantify the shiver.

Finally, the biological explanation relates the origins of human thought to the tremendous changes in temperature at its birth. It might be that we can observe this relation between the mechanisms that regulate cognition and the mechanisms that regulate temperature because of the particular context in which thought saw the light of day. In other words, a shiver might have very well accompanied the first human idea. Since then, every time we grasp something important, perhaps we repeat the gesture.