Being a Self

An excerpt from Being You: A New Science of Consciousness
by Anil Seth

Underneath the layered expressions of selfhood involving memories of past and plans for the future, before the explicit sense of personal identity, beneath the ‘I’ and even prior to the emergence of a first-person perspective and experiences of body ownership, there are deeper layers of selfhood still to be found. These bedrock layers are intimately tied to the interior of the body, rather than to the body as an object in the world, and they range from emotions and moods—what psychologists call ‘affective’ experiences—to a basal, formless, and ever-present sense of simply ‘being’ an embodied, living organism.

We’ll start our exploration of these depths with emotions and moods. These forms of conscious content are central to the experience of being an embodied self, and—like all perceptions—they too can be understood as Bayesian best-guesses about the causes of sensory signals. The distinctive thing about affective experiences is that the relevant causes are to be found within the body, rather than out there in the world.

When we think about perception, we tend to think in terms of the different ways in which we sense the outside world – in particular the familiar modalities of sight, hearing, taste, touch, and smell. These world-oriented varieties of sensation and perception are collectively called exteroception. Perception of the body from within is known as interoception—it is the ‘sense of the internal physiological condition of the body’. Interoceptive sensory signals are typically transmitted from the body’s internal organs—the viscera—to the central nervous system, conveying information about the state of those organs, as well as about the functioning of the body as a whole. Interoceptive signals report things like heartbeats, blood pressure levels, various low-level aspects of blood chemistry, degrees of gastric tension, how breathing is going, and so on. These signals travel through a complex network of nerves and deep-lying brain regions before arriving at parts of the cortex specialised for interoceptive processing—in particular the insular cortex. The key property of interoceptive signals is that they reflect, in one way or another, how well physiological regulation of the body is going. In other words, how good a job the brain is doing of keeping its body alive.

Interoceptive signalling has long been connected with emotion and mood. Back in 1884, William James and—independently—Karl Lange argued that emotions were not the ‘eternal and sacred psychic entities’ of the ancient philosophers, but were instead perceptions of changes in bodily state. We don’t cry because we are sad, we are sad because we perceive our bodily state in the condition of crying. The emotion of fear, in this view, is constituted by (interoceptive) perception of a whole gamut of bodily responses set off by the organism recognising danger in its environment. For James, the perception of bodily changes as they occur is the emotion:

“We feel sorry because we cry, angry because we strike, afraid because we tremble, and not that we cry, strike, or tremble, because we are sorry, angry, or fearful.”

James’ theory encountered strong resistance at the time, in part because it subverts the common, intuitive, how-things-seem notion that emotions cause bodily responses, rather than the other way around. It seems as though the feeling of fear—for example, when we happen upon a grizzly bear—is what causes our heart to race, our adrenaline to pump, and our feet to flee. By now, though, we’ve learned to be sceptical about taking how things seem as a guide to how they actually are—so it would be unwise to dismiss the Jamesian view on this basis alone.

A more substantive concern was that bodily states may be insufficiently distinct from each other to support the full emotional range that we humans experience. While the specifics of this concern are still debated, a powerful response emerged in the 1960s with ‘appraisal’ theories of emotion. On these theories, emotions are more than just read-outs of changes in bodily state. They depend on a higher-level cognitive appraisal or evaluation of the context in which the physiological changes take place.

Appraisal theories solve the problem of emotional range because each specific emotion now no longer needs a dedicated bodily state. Two closely related emotions—for example, listlessness and ennui—might be based on the same bodily state. The distinct emotions would emerge from different cognitive interpretations of this shared bodily condition. Of course, it might equally be true—and I suspect that it probably is true—that every emotion does indeed have a distinct embodied signature, with the fine details of their distinguishing features just being very difficult to detect… it occurred to me that a way to overcome the limitations of appraisal theories was to apply the principles of predictive perception, and to treat emotions and moods—and affective experiences in general—as distinctive kinds of controlled hallucination. Surprisingly, this did not seem to have been done before.

I called the idea interoceptive inference. Just as the brain has no direct access to the causes of exteroceptive sensory signals like vision, which are out there in the world, it also lacks direct access to the causes of interoceptive sensory signals, which lie inside the body. All causes of sensory signals, wherever they are, are forever and always hidden behind a sensory veil. Interoception is therefore also best understood as a process of Bayesian best guessing, just like exteroceptive perception. In the same way that ‘redness’ is the subjective aspect of brain-based predictions about how some surfaces reflect light, emotions and moods are the subjective aspects of predictions about the causes of interoceptive signals. They are internally-driven forms of controlled hallucination.