Thought happens not only inside the skull but out in the world, too; it’s an act of continuous assembly and reassembly that draws on resources external to the brain.

For another: the kinds of materials available to “think with” affect the nature and quality of the thought that can be produced.

And last: the capacity to think well — that is, to be intelligent — is not a fixed property of the individual but rather a shifting state that is dependent on access to extra-neural resources and the knowledge of how to use them.

One major aspect of this extended mind is our capacity for interoception — an awareness of the internal sensations of the body that gives us a kind of non-conscious knowledge, which we might term intuition but which is rooted in concrete embodied experience and somatic pattern-recognition. We might not detect the signals consciously, but we respond to the information they carry.

When a potentially relevant pattern is detected, it’s our interoceptive faculty that tips us off: with a shiver or a sigh, a quickening of the breath or a tensing of the muscles. The body is rung like a bell to alert us to this useful and otherwise inaccessible information. Though we typically think of the brain as telling the body what to do, just as much does the body guide the brain with an array of subtle nudges and prods.

Researchers have even captured the body in mid-nudge, as it alerts its inhabitant to the appearance of a pattern that she may not have known she was looking for.