The question is neither straightforward nor silly. Brains are complex things, and so are the faces that eyes are often tucked into.
Dolphins, dogs, monkeys, birds, goats, people and other organisms, for example, are primed to automatically follow the gaze of both familiar and unfamiliar species. But we don't know how this widespread gaze-recognition circuitry works, or what image draws our attention. Is it the eyes themselves, or their typical central location, or the complexities of face, or something else?
"Resolving this issue will ... inform why a subset of people may fail to select the eyes of others, and what brain mechanisms may be compromised, as in the case of autism," wrote a team of researchers in a Biology Letters study published online this week. "It has been argued, however, that distinguishing between these two accounts may be impossible because human eyes are in the centre of the face."
To grasp for an answer, study leader Alan Kingstone, a cognitive scientist at the University of British Columbia, enlisted the help of his 12-year-old son - and images of monsters from the kid's Dungeons & Dragons fantasy video game.
Kingstone and two colleagues gathered images of people, human-like monsters (e.g. a hybrid deer-man), and inhuman monsters (e.g. a rock golem with eyes on its hands) from the game. They then plugged the images into an eye tracking system to follow saccades - i.e. rapid eye movements - of people they recruited to look at the photos.
The results showed that, regardless of the creature, people first looked directly at the geometric center of the figure. For humans and humanoids, their eyes then drifted vertically. Monsters, meanwhile, prompted sporadic eye movements.
Yet in all cases one truth held up: People looking at the photos first searched for the eyes and, once they found them (on a head, hands, torsos, or otherwise), their gaze locked onto the peepers before moving to other body parts.
Aside from demonstrating that people process images of monsters and humanoids as human - at least when it comes to their eyes - there's a more practical take-away for people on the autistic spectrum, who often lack a fixation on eyes.
"Our conclusion that human gaze selection is mediated by a specialized brain mechanism, sensitive to the eyes rather than only the head, sheds light on individuals with autism who often fail to select the eyes of others," the authors wrote. "[E]fforts to train individuals with autism to look at others in a typical manner should focus on the selection of the eyes of others rather than targeting the head alone."