You can tell a lot about a person just by looking at their face. From a glance, we can glean information about a person’s emotional state, sex, age, ethnicity, where their attention is focused and, of course – if we recognise them – who they are.

But where should you look on a face to get the best look – that is, where should we focus our gaze to gather the most information?

In their new study published in PNAS, Matthew Peterson and Miguel Eckstein – from the University of California Santa Barbara – shed some light on this question through the use of eye-tracking techniques.

Tracking eyes

There is a long history of research into eye movements, stretching back to Aristotle. In the 1950s and 1960s, Alfred Yarbus, a Russian scientist, demonstrated that when people look at a face they tend to look at the eyes and mouth, in a triangular scanning pattern.

To measure eye movements, Yarbus developed suction caps that were attached to the surface of the eye like contact lenses (see image below). Small https://c479107.ssl.cf2.rackcdn.com/files/18450/area14mp/cb8czv3r-1354855791.jpgmirrors were attached to the caps to reflect light, and these reflections were used to measure eye movements.

Most modern eye movement recording techniques are much less invasive; they are compact and can be used to measure eye movements in both children and adults. Applications are even being developed to allow eye tracking with nothing more than a webcam.

That said, precise information about where people are looking typically requires a set-up involving a small camera connected to a computer that monitors the reflection of infrared light from the cornea of the eye and the position of the pupil.

Look into my eyes

The studies by Yarbus showed that when given the freedom to explore a face for an extended period of time, people from Western cultures will concentrate their fixations mainly on the eyes, with some looks also to the mouth.

In these cultures it is important to look a person in the eye during social interactions to avoid appearing insincere or even a bit shifty.

In East Asian cultures, where eye contact may be considered impolite or disrespectful, people have been shown to focus more on the nose.

But regardless of where they are looking on the face there is evidence that both cultures extract information from the eyes.

This suggests that perhaps the eye region is important in conveying information about the face.

In the blink of an eye

The new paper by Peterson and Eckstein suggests it’s best to look just below the eyes in order to most effectively extract information from a person’s face.

To reach their conclusion, the researchers presented test subjects with faces very briefly, allowing them time for only a single movement of the eye. The subjects were then asked to make common, socially important judgments, such as determining the identity, gender or emotion of the face.

When people were able to choose where to look, they tended to look at an area between and just below the eyes. This was the preferred area regardless of whether people were judging identity, expression or gender.

When people were only allowed to look at other regions of the face (e.g. forehead, tip of the nose, mouth), their ability to judge identity, expression or gender was reduced. These results suggest that the area people naturally prefer to look at – the area just below the eyes – provides access to information useful in performing these tasks.

Peterson and Eckstein also wanted to know whether eye movements are functional – that is, do people consistently look at the area which will maximise accuracy of the task?

To do this they used a computer-based modelling program – an artificial “ideal observer” – to identify the optimal area to look on the face to extract the largest amount of information. The area identified by the computer program corresponded closely to the patterns observed in the participants.

Together the results from the human and computer observers suggest that when time is short, our visual systems unconsciously guide our eyes to the best spot on the face to perform the task.

Looking the wrong way

So why does all this matter?

At a fundamental level, being able to discern information from a face quickly and accurately may have conferred an evolutionary advantage over the course of human history.

Determining whether a person walking towards you is a friend or foe is important because the quicker you can determine whether that person looks angry, the more time you have to plan whether to flee or fight.

On a more focused level, understanding where it is best to look may help us understand why some people have difficulty recognising emotion and identity from faces. People with schizophrenia and autism spectrum disorders, for instance, often have trouble reading faces.

Studies have suggested these difficulties may be associated with atypical eye movement patterns.

Similarly, there is evidence that people with prosopagnosia (“face-blindness”) – who have severe difficulty recognising the faces of familiar people – do not look at the eyes but that training to improve face recognition can increase looks to the eyes.

So next time you’re looking at someone’s face, remember: there’s more to this seemingly basic process than meets the eye.