Researchers in Japan suggest there's a surprising neurological reason why people avert their gaze occasionally during conversation. Reporting in the journal Cognition, they write that eye contact actually "disrupts resources available to cognitive control processes during verb generation." In other words, when you need to come up with certain words under certain circumstances, maintaining eye contact depletes the very brain resources you need to find the word. So you look away. To test this, the researchers asked 26 participants to make eye contact with a computer-generated face while playing a word association game, reports Business Insider. Looking at the face didn't seem to interfere with their ability to come up with verbs easily associated to nouns—like the word "scissors" prompting the person to think of "cut."
But when nouns were more difficult—for example, if they had too many associations or were a little obscure—it took participants longer to think of a verb while maintaining that eye contact. As a post at Science Alert sums up: "While making eye contact and holding a conversation is certainly possible, this is evidence that they can both draw on the same pool of cognitive resources, and sometimes that pool starts to run a little dry." The researchers didn't parse out possible cultural influences, but Scientific American suggests that if looking away while thinking is cross-cultural, "perhaps cultures with less emphasis on eye contact enable deeper thinking during a given conversation." (Eye contact is forbidden in a certain Minnesota locale.)