Thinking doesn’t happen only in the brain.
"More than 20 years ago, two philosophers, Andy Clark and David Chalmers, wrote a journal article that opened with a question: “Where does the mind stop and the rest of the world begin?” Now, that question would seem to have an obvious answer, right? The mind stops at the head. It’s contained within the skull. But Clark and Chalmers maintained that this assumption—as common as it is—is wrong. The mind, they said, takes elements from outside the head and draws them into the thinking process. These mental “extensions” allow us to think in ways our brains couldn’t manage on their own. They called this phenomenon 'the extended mind.'”
Annie Murphy Paul has just published a book on the topic, a book that she summaries here.
Book Summary: Extended Mind: The Power of Thinking Outside the Brain