What were you thinking about a second ago? Or, to cut to the chase, how were you thinking about it? It’s a deceptively tricky question to answer.

Maybe you were internally speaking the words you were reading, seeing a related image in your mind’s eye, or having an emotional response. It’s also possible you had a combination of these thoughts, and others, going on in your head at once… or that you were thinking of something else, in some other way, entirely.

Whatever was happening, it’s likely that your true inner experience – what you were thinking about just before you started trying to figure out what you were thinking about – is now lost to the mists of time.

Interrogating what’s going on inside our own minds doesn’t seem like it should be a difficult task. But by trying to shine a light on those thoughts, we’re disturbing the very thing we want to measure in the first place. Or as American philosopher William James put it in 1890: “The attempt at introspective analysis… is in fact like seizing a spinning top to catch its motion, or trying to turn up the gas quickly enough to see how the darkness looks.”

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Psychologist Russell Hurlburt at the University of Nevada, Las Vegas, has spent the last few decades training people to see inside their own minds more clearly in an attempt to learn something about our inner experiences at large. Though many individual studies on inner speech include only a small number of participants, making it hard to know whether their results apply more widely, Hurlburt estimates he’s been able to peek inside the minds of hundreds of people since he began his research. What he’s found suggests that the thoughts running through our heads are a lot more varied than we might suppose.

For one, words don’t seem to feature as heavily in our day-to-day thoughts as many of us think they do. “Most people think that they think in words, but many people are mistaken about that,” he says.