There’s an idea in David Eagleman’s Livewired that I haven’t been able to stop thinking about this week. Here’s the setup: our brains have a physical map of our bodies printed on them. You touch this part of your brain—blam!—your elbow just felt that. You go down and—double blam!—it’ll feel as if your forearm has been pressed in the same way.

That’s fine and interesting and all, but what’s more interesting about this discovery is how different regions of your brain are in constant conflict with one another. If you close your eyes for a few days then your other senses will literally, physically, override those parts of the brain that are devoted to your eyes—you’ll hear better, feel better. David calls this “cortical takeover” throughout the book.

One hypothesis in the book about why we dream is likewise disturbing: we dream so that the parts of our brain that control our legs or ears or nose don’t “override” our eyes during the night. That’s wild! But then it all leads to this:

This hypothesis leads to a prediction for the distant future, when we discover life on other planets...

...(I love the positive note here; not if, but when)...

Some planets (especially those orbiting red dwarf stars) become locked into place, such that they always have the same surface facing their star: they thus have permanent day on one side of the planet, and permanent night on the other. If life-forms on that planet were to have livewired brains even vaguely similar to ours, the prediction would be that those on the daylight side of the planets might have vision like us but would not have dreams. The same prediction would apply for very fast-spinning planets: if the nighttime is shorter than the time of a cortical takeover, then dreaming would also be unnecessary. Thousands of years hence, we might finally know whether we dreamers are in the universal minority.

There’s a lot of fun, pop sci-fi in this book so far and so I’d highly recommend it.