Struggling to tell faces of other races apart may have more to do with perception than prejudice, a Kiwi researcher says.

Unravelling our visual perceptions of others has been the focus of a growing research effort by the head of the University of Auckland's school of psychology, Professor Will Hayward.

When he shifted to Hong Kong in the late 1990s, he found for himself how the brain could struggle to distinguish between people of other ethnicities.

"It sounds un-PC, but I had great difficulty telling my Chinese students apart from one another," he said.

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"I would often mistake one student for another."

But he soon discovered the feeling was mutual.

"They couldn't figure out why I had trouble with them; they said all white people looked identical to each other."

By the time he returned to New Zealand this year, his brain had adapted to pick up differences.

He told the Herald he was keen to continue exploring the science of face perception - to which he last night devoted his inaugural lecture - in his new role in Auckland.

"It's a big topic, and over the last 20 years with globalisation, it's an experience a lot more people are having."

For most of us, he said, seeing was effortless - we opened our eyes and the world was instantly available.

"But the ease of the process belies its complexity, and we are only just beginning to understand how the brain creates our visual sense of the world."

No matter where we come from, our brains are trained to distinguish the features of those we surround ourselves with.

But if those faces are from one ethnicity, then we become overspecialised.

This was particularly noticeable when travelling to countries where the culture was unfamiliar.

"These people aren't more similar to each other than the ones we are used to, but our visual system doesn't know what to pay attention to."

There was also an aspect of social psychology at play, as the brain could automatically group people of other ethnicities together.

"So it's kind of a mixture of how you view, but also the way you think about the person you are looking at."