By Christian Jarrett

When someone’s talking to you, have you noticed how they seem to keep breaking off eye contact, as if finding it hard to both talk and look you in the eye at the same time? Similarly, when you’re explaining something to someone or telling them a story, do you find yourself looking away from their eyes, so that you can concentrate on what you’re saying? A pair of Japanese researchers say that this happens because eye contact has a “unique effect” on our “cognitive control processes”. Essentially, mutual gaze is so mentally stimulating that it can be tricky to think straight and maintain eye contact at the same time.

Past research has shown that eye contact interferes with other mental tasks such as those involving visual imagination. Arguably this isn’t so surprising because both eye contact and visual imagination are obviously tapping the same mental domain. In their new paper in Cognition, Shogo Kajimura and Michio Nomura tested whether eye contact also interferes with our ability to generate verbs in a word task, and whether this happens in all cases, or only when the verb generation task is made extra difficult.

Twenty-six participants were asked to look directly at a stranger’s face shown on-screen, while simultaneously performing an auditory verb generation task. Six men’s and women’s faces featured in the study, and were shown either looking straight at the participant or with their gaze averted. The faces were video animated so they appeared naturally, blinking and breathing. Each trial, the participant looked at the face, heard a noun, then their task was to respond out loud with a verb that could be used with the noun in a sentence.

The researchers used a range of nouns that are easier or harder to respond to, based on how strongly associated to the noun any related verbs are (i.e. retrieval demands high or low); and whether one possible response is much more dominant than any others versus there being many equally plausible alternatives (i.e. selection demands high or low).

To take one example, the noun “milk” is easy on both measures, because it’s strongly associated with “drink” and much more so than any other verb.

The key result is that participants were much slower at the verb generation task when making eye contact with the face on-screen, as opposed to when the face’s gaze was averted, but only in the most difficult version of the verb generation task, when retrieval and selection demands were high.

Kajimura and Nomura said this shows that eye contact doesn’t directly interfere with mental processes specifically related to verb generation – if it did, then performance times ought to have been longer for eye contact across easy and difficult versions of the verb task. Instead, they said the results are consistent with the idea that eye contact drains our more general cognitive resources – the kind that we need to draw on when some other task, such as speaking, becomes too difficult to be handled by domain-specific resources. That’s why the more complicated the story you’re telling (or excuse you’re making), the more likely you are to need to break off eye contact.

Looking away when we’re talking is something most of us do instinctively as adults, but this isn’t necessarily the case for children. Past research has shown that young children can benefit from being taught to avert their gaze when they’re thinking.

—When we cannot speak: Eye contact disrupts resources available to cognitive control processes during verb generation

Image via Craig Sunter/Flickr

Christian Jarrett (@Psych_Writer) is Editor of BPS Research Digest