Our language weighs heavily with idioms and clichés about the human gaze. Whether they're windows to the soul, or we're staring daggers, eye contact communicates more about our intentions than words ever could alone.
Poetry aside, the mechanisms behind our response to the gaze of another human are less than clear. Is it an emotional reaction that grabs our attention, or is it our attention that's hooked, with emotions coming along for the ride?
Each step in the sequence recruits entirely different areas of the brain, so understanding the process could help us better understand why eye contact makes some people so incredibly uncomfortable.
To provide some insight into this puzzle of the human gaze, psychologists Nicolas Burra and Dirk Kerzel from the University of Geneva in Switzerland recruited a number of volunteers to assist in a series of eye-catching experiments.
The first involved 22 recruits observing a series of animated images representing 40 stoic-faced strangers. Some of the short clips had the stranger looking to one side, before shooting a look down the barrel of the camera Blue Steel style. Others were reversed, with brief eye contact broken by a deviating glance.
Each clip appeared for a period of time ranging from 986 milliseconds to nearly 1.5 seconds, a duration on par with the kinds of eye glances we trade during social interactions.
All the subjects had to do was determine whether the moving image had been visible for a short duration or a long one.
"While deviated glances do not distort our perception of time, we found that, on the contrary, when glances crossed, the participants systematically underestimated the duration of these eye contacts," says Burra.
The first experiment's results were compared against trials using non-social subjects and static photographs of faces, where no significant differences in time estimates could be seen.
"It seems that not only a gaze, but also a movement is required," says Burra.
In follow up experiments involving new sets of volunteers, faces were respectively flipped, and reduced to a narrow band for the eyes. Once again, time seemed to pass slightly faster when eyes met with a brief stare.
That underestimation of the passing seconds implies our attention wiring is occupied the moment we make eye contact, leading us to perceive the time that passes in a locked gaze as slightly shorter than it really is.
Had the subjects experienced time slowing, much as we might sense when dealing with a spider crawling through our field of vision, it would imply our emotions were more heavily involved.
What's more, the presence of an easily recognizable face surrounding the eyes isn't a necessary feature. Our eyes are more than capable of stealing a few moments all on their own.
"From an early age, we learn to decipher the feelings and intentions of our interlocutors through their eyes," says Burra.
"Thus, meeting someone's gaze is a very common social situation, but it always leads to a particular feeling."
For some, especially those on the autism spectrum, that particular feeling isn't at all pleasant.
In light of this research, the attention devoted to extended durations of eyeballing other humans could be sapping our energy faster than we're used to.
This research was published in Cognition.