Interoception is the sense of the internal state of the body. Where exteroception maps the outside world through sight, hearing, smell, taste, and touch, and proprioception tells you where your limbs are in space, interoception is the felt sense of the interior: heart rate, breathing, hunger, thirst, fullness, temperature, pain, the need to pee, the subtle-but-powerful signal of "something is off" or "I am fine".
The term was coined by the English neurophysiologist Charles Sherrington in 1906, alongside exteroception and proprioception, to distinguish signals arriving from inside the body from those arriving from outside it. Receptors in the gut, heart, lungs, blood vessels, and bladder relay information up through the vagus nerve to the brainstem and from there into the insular cortex — the part of the brain that appears to build the felt sense of being alive, and of being you.
Why it matters
Interoception is deeply entangled with emotion. The racing heart, the clenched stomach, the warmth in the chest — these are the bodily ingredients from which the brain constructs feelings like fear, joy, grief, or love. Antonio Damasio's somatic marker hypothesis and Lisa Feldman Barrett's theory of constructed emotion both place interoception at the center of how emotions arise in the first place. Without a body to feel, the argument goes, there is nothing for emotion to be about.
It is also the quiet substrate of intuition. "Gut feeling" is not purely metaphorical — the gut is innervated by roughly five hundred million neurons, and it talks to the brain constantly. When you sense that a negotiation is going sideways before you can say why, that is often interoception relaying evidence your conscious mind has not yet parsed.
When it varies
Interoceptive awareness is not uniform across people. Some can count their heartbeat without touching their wrist; others can be mid-panic-attack and genuinely not notice that anything is happening. Low interoception is common in autism, alexithymia (difficulty identifying one's own emotions), eating disorders, depression, and chronic pain conditions. High interoception can be a superpower for athletes, meditators, and musicians — but when it tips into hypervigilance, it becomes the engine of health anxiety and somatic obsession.
It is one of those concepts that, once named, quietly reshapes how you think about a lot of things: meditation, mindfulness, trauma responses, the "sixth sense" that is not sixth at all. It is the first sense, the oldest one, the one you have been using without a name since you had a body.