When you know you're being watched by somebody, it's hard to pretend they're not there. It can be difficult to block them out and keep focus, feeling their gaze bearing down upon you.
Strangely enough, it doesn't even seem to really matter whether they're alive or not.
In new research, scientists set up an experiment where people played a game against a robot.
If the robot looked up at the human players during the session, it ended up affecting the participants' behavior and strategy in the game – a change that could be discerned in measurements of their neural activity recorded by electroencephalography (EEG) during the experiment.
"If the robot looks at you during the moment you need to make a decision on the next move, you will have a more difficult time in making a decision," says cognitive neuroscientist Agnieszka Wykowska from the Italian Institute of Technology.
"Your brain will also need to employ effortful and costly processes to try to 'ignore' that gaze of the robot."
In the experiment, 40 participants sat across from an iCub humanoid robot, competing in a game of 'Chicken' on a horizontal computer screen, in which two simulated cars rushed head-on towards one another.
Just before the moment of impact, the game would pause, and the participants were asked to look up at the robot – which would either meet their gaze, or look away. During this instant, the participants had to decide whether to let their cars run ahead, or to deviate to the side.
The results of the experiment showed that the robot's return gaze didn't influence the choices individual human players made, but it did cause their response time to slightly increase, with participants generally responding faster in the game when the iCub averted its eyes.
"In line with our hypothesis, the delayed responses within-subjects after mutual gaze may suggest that mutual gaze entailed a higher cognitive effort, for example, by eliciting more reasoning about iCub's choices, or higher degree of suppression of the (potentially distracting) gaze stimulus, which was irrelevant to the task," the researchers explain in their paper.
According to the researchers, this change in player behavior corresponded with a change in neural activity called synchronized alpha activity – a brain wave pattern that's previously been associated with suppressing attention.
What's more, when viewed across the entire experiment, higher exposure to averted gaze (where the robot did not stare back) among participants seemed to help players disengage from the social interaction with the iCub, and focus on their gameplay with less distraction.
Given the iCub is a humanoid robot – designed loosely to mimic the shape and appearance of people – it's not altogether surprising perhaps that a robot's gaze can trigger our usual attentional processes.
But it could have implications for the design of more advanced and interactive robots in the future, the researchers say.
"Robots will be more and more present in our everyday life," Wykowska says.
"That is why it is important to understand not only the technological aspects of robot design, but also the human side of the human-robot interaction… how the human brain processes behavioral signals conveyed by robots."
The findings are reported in Science Robotics.