Think of one word that can form a compound word with “sauce,” “pine” and “crab.”

I’ll wait . . . .

Time’s up: did you come up with “apple,” to make “applesauce,” “pineapple” and “crabapple”? OK, let’s consider that a warmup. Try the same exercise—finding a word to make a compound word—with “bump,” “step” and “egg.”

Did “goose” pop into your head?

One more: for “back” “clip” and “wall.” . . . .It’s “paper,” for “paperback,” “paperclip” and “wallpaper.”

If you’re like many people, you tried to solve each problem methodically, first finding a word that would go with, say, “sauce” and then trying it out with “pine” and “crab.” But if you’re like most people in a more important way, if you solved these brain-teasers you did so not through this grind-through-the-possibilities approach, but through insight. That is, you thought a little and then, wham, the answer suddenly hit you.

Scientists have approximately no idea how this happens.