The Science of Mental Fitness

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. This neurological system has done a pretty good job
of modelling the world such that the ancestors of modern human
beings avoided getting eaten by sabre-toothed tigers before
procreating, but the human brain remains relatively easy to fool.
Optical illusions, dreams, hallucinations, altered states of
consciousness, and the placebo effect are just a handful of
familiar cases where what the brain perceives does not correspond
to whatever is actually occurring. The formation of a coherent
model of the world often relies on imagined components. 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.