A tilt of the head leads people to look more at the eyes, making them more approachable and less threatening, a study suggests.

Every time we look at a face, we take in a flood of information effortlessly: age, gender, race, expression, the direction of our subject's gaze, and even their mood.

Faces draw us in and help us navigate relationships and the world around us, according to the study published in the journal Perception.

Understanding how facial recognition works has great value - particularly for those whose brains process information in ways that make eye contact challenging, including people with autism.

Helping people tap into this flow of social cues could be transformational.

People who are reluctant to make eye contact may also be misperceived as disinterested, distracted, or aloof, he noted.

Researchers also know that we have a terrible time "reading" a face that's upside down.

It is as if our neural circuits become scrambled, and we are challenged to grasp the most basic information.

Much less is known about the middle ground, how we take in faces that are rotated or slightly tilted.

"We take in faces holistically, all at once - not feature by feature. But no one had studied where we look on rotated faces," said Davidenko.

He used eye-tracking technology to get the answers, and what he found surprised him: The left-gaze bias completely vanished and an "upper eye bias" emerged, even with a tilt as minor as 11 degrees off centre.

"People tend to look first at whichever eye is higher," he said.

"A slight tilt kills the left-gaze bias that has been known for so long. That is what is so interesting. I was surprised how strong it was," said Davidenko.

More importantly for people with autism, Davidenko found that the tilt leads people to look more at the eyes, perhaps because it makes them more approachable and less threatening.