D: Hey Yaël, remember those “spot the difference” games you probably played as a kid?
Y: You mean when there’d be two images that looked nearly identical but had a few details that were different? Yeah, those were fun. And really hard! In fact, now that you mention it, I wonder why those little details were so hard to detect?
D: Actually, the reason it’s so hard is because the brain didn’t evolve to notice every little detail when we see something. That’s especially true when we try to see minute differences in pictures where most of the details are the same. Psychologists call this “change blindness.”
Y: Hmm. OK. I guess I’m a little surprised, though. I would have thought that our brains would evolve specifically to notice little details. I mean, out on the African savannah, wouldn’t our prehistoric ancestors have needed to be really detail oriented in order to survive?
D: Yes, but only to a point. Think about it. Say you’re an ancient human out on a hunt and you have to be alert to predators. You’d want to focus in on the most important things, right?
D: But if you were tuned to notice every little detail around you, you’d have a hard time focusing on the things that really matter. So, in order to focus our attention, our brains sort of ignore details it registers as unimportant.
Y: I see. So, when we look at those “spot the difference” pictures, we’re just not wired to immediately note every single thing.
D: Yep. Which is why the little differences are usually in the background.