“What’s the right amount of eye contact?” is probably one of those questions where it’s best not too think too much about the answer. Kind of like “what muscles do you move when you walk?” or “how do you keep from falling off your bicycle?”

If you do think about it, though, you might notice that people often make more eye contact when they’re listening than when they’re speaking. Part of the reason for this is obvious: if someone’s talking to you, you generally want to give the impression that you’re paying attention to what they have to say.

But another reason is more subtle: it may be that talking and making eye contact at the same time is just too darn much for our brains to deal with. At least that’s what the results of research published this month in the journal Cognition are suggesting.

In the study, psychologists from Kyoto University had people generate words while looking at pictures of faces. Some of the faces were “looking at” the participants while others had their eyes averted.

It turned out that people were slower at generating words when looking at the pictures that were making eye contact.

One possible explanation suggested by the researchers is that generating words and making eye contact rely on some of the same cognitive resources. To say that another way, it may be that some of the parts of the brain involved in eye contact are also involved in generating words. So when you’re talking, breaking eye contact has the benefit of letting you dedicate those cognitive resources to forming a coherent sentence.

Of course, it’s not that talking and making eye contact at the same time is as a rule hopelessly impossible. It’s that simultaneously speaking and meeting someone’s gaze might be just enough work that you look away a little more than you otherwise would.

The brain is incredibly skilled at doing multiple things at once without having you realize it. But sometimes, even the brain needs some “me” time where it can just focus on one thing!

Image: Flickr/See-ming Lee