It’s a testament to the strength and versatility of the human brain that anyone with at least half of one tends to assume that their senses give them direct access to objective reality. The truth is less straightforward and much more likely to induce existential crises: the senses do not actually provide the brain with a multifaceted description of the outside world. All that the brain has to work with are imperfect incoming electrical impulses announcing that things are happening. It is then the job of neurons to rapidly interpret these signals as well as they can, and suggest how to react. As it turns out, this pseudo-reality in one’s imagination can be so convincing that it can have unexpected effects on the physical body.