A University of Auckland professor who admitted he struggled to tell his students apart has researched the psychology behind the difficulty people have recognising faces of different ethnicities.

When Professor Will Hayward was teaching in Hong Kong he found it difficult to recognise his students.

"It sounds un-PC but I had great difficulty telling my Chinese students apart from one another," he says. "I would often mistake one student for another," he said.

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

He developed a research programme on face identification for people of different ethnicities.

"For most of us, seeing is effortless. We open our eyes, and the world is instantly available to us.

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."

People develop expertise for seeing the precise differences between faces, he said.

However, if those faces were all from one ethnicity, people struggled to see the differences in faces of a different ethnicity.

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

"The key thing is that these new people aren't actually more similar to each other than the ones we are used to, but our visual system doesn't know what to pay attention to," he said.

"Spending time in the new location definitely gives you more expertise at face identification, but it does require active practice."

The science of face perception is the topic of Professor Hayward's inaugural lecture, the Psychology of Seeing.

Professor Hayward's lecture would give an overview of the field of visual perception, which combined experimental psychology and cognitive neuroscience.

He would illustrate how the eyes were only the beginning of the visual system, and that major parts of the brain were devoted to interpreting visual information.

Professor Hayward led the Department of Psychology at the University of Hong Kong before taking up his current role as Head of the School of Psychology at University of Auckland.

The lecture will be held on Level 0 of the Owen G Glen Building in Lecture Theatre OGGB3 from 6pm to 7pm tonight.

- APNZ