“A typical neuron makes about ten thousand connections to neighboring neurons. Given the billions of neurons, this means there are as many connections in a single cubic centimeter of brain tissue as there are stars in the Milky Way galaxy.” David Eagleman

This short, accessible, and frequently amusing book opens with “The Half Lesson: Your Brain Is Not for Thinking.” It’s not? Already my mind boggled. Then what’s it for? Wipe your mind of whatever you were thinking (ha) and prepare for a shock.

Your brain’s most important job is predicting your body’s energy needs before they arise so you can efficiently do what needs doing and survive to pass your genes on to the next generation.

In seven and a half deeply subversive essays, author Lisa Feldman Barrett, a groundbreaking research neuroscientist, explodes pretty much everything I’ve understood about the brain and how it works. That’s quite a statement given I’m a psychiatrist—my medical specialty is the brain. Check out the following:

Memories are not filed like paperwork—that’s a metaphor. They are actually recreated on demand. And not necessarily by the original neurons. What! Yes.

The human brain is large but so are our bodies. So, proportionally, our brains are no bigger than the brains of other mammals. What?! Yes.

Nature uses the same manufacturing plan to build our brains and those of all mammals (and most likely reptiles and other vertebrates). No! Yes.

The idea that natural selection has targeted the human brain to evolve to the top of the animal pyramid is wrong. We are not special or superior, simply different.

The brain is not organized into three layers: lizard (survival), limbic (emotional) and neocortex (rational). It’s not? Nope. That too is a metaphor.

The brain is a vast, flexible, plastic network. That’s not a metaphor but a description of the brain’s actual structure.

Any one neuron can do more than one thing. Groups of neurons can configure themselves into an enormous number of different patterns.

The human mind results from the brain network’s functional complexity, not from the brain’s physical size.

This complexity is organized to manage the body’s energy budget, in a never-ending cost/benefit analysis that optimizes our physical survival. That agenda drives all our choices and behaviors and puts what we think of as “rational” in a radically different context—that of the body rather than of the logical mind.

It came as a revelation that what the brain is actually doing under the hood translates into our experience of thinking, imagination, creativity, mental illness, our sense of continuity of ourselves as we age, relationships, culture, and even the meaning of life.

The brain—a three-pound jelly trapped in the dark of a small bone box—creates our reality. Let that sink in.

“It’s still magic even if you know how it’s done.” Terry Pratchett