Mind Hacks

Hack #76. To Be Noticed, Synchronize in Time

We tend to group together things that happen at the same time or move in the same way. It’s poor logic but a great hack for spotting patterns.

It’s a confusing, noisy world out there. It’s easier to understand the world if we perceive a set of objects rather than just a raw mass of sensations, and one way to do this is to group together perceptions that appear to have the same cause. The underlying assumptions involved manifest as the gestalt grouping principles, a set of heuristics used by the brain to lump things together (see [Hack #75] for the simplest of these, used for vision).

Perhaps the most powerful of these assumptions is termed common fate. We group together events that occur at the same time, change in the same way, or move in the same direction. Imagine if you saw, from far off, two points of light that looked a bit like eyes in the dark. You might think they were eyes or you could just put it down to a coincidence of two unrelated lights. But if the points of light moved at the same time, in the same direction, bounced with the characteristic bounce of a person walking, you’d know they were eyes. Using behavior over time allows you to stringently test spatial data for possible common cause. If the bouncing lights pass the common fate test, they’re almost certainly a single object. Visual system tags this certainty by providing you with a correspondingly strong perceptual experience; if some things move together, it is almost ...