If we told you to think about anything you want - fat dogs, doughnuts, giant Christmas trees - but whatever you do, don't think about a white bear, chances are you're gonna think about a white bear. It doesn't matter how intelligent you are or how much self-control you can exert, our thoughts can be very difficult to restrain. Even thinking about not thinking about a white bear means you're thinking about a white bear. But why is this? Well, to understand that, we first have to understand what a thought actually is.
As the Explanimator video above points out, there are two possible definitions of a thought. Either it's a part of the material world - physical patterns of electricity generated by the neurons in our brains - or it's a part of something else, some kind of cosmic consciousness that floats around the Universe completely undetectable by the instruments of modern science. Okay, unsurprisingly, the former definition is the one we're going to focus on here...
So we know that the 100 billion or so neurons in our brains exchange up to 1,000 electrical signals with each other every second, which means right now, a whole lot of activity is going on up there. But all of this activity rarely bubbles up to the surface as a conscious thought. Like, say, thinking about a white bear. You did it again, didn't you?
Nope, a lot of this activity is just the brain processing raw perception, so recognising the stimuli that are taken in by your various senses to help you understand your environment. The difference between perception and thoughts is that while perception is tied to stimuli, thoughts aren't. Which means you can think about a white bear without there being any white bears in your vicinity.
A thought even allows us to picture things that aren't perceptable at all, says the video above, like imagining what dark matter looks like, or what it would be like to reach the event horizon of a black hole.
But where does a thought actually come from, and by what mechanism does it stick around in our brains? While scientists haven't quite figured this out yet, they've come up with some pretty fascinating hypotheses. I'll let the latest episode of Explanimator run through those with you, but in the meantime, don't think about... there he is!