The experts that can outsmart optical illusions

14 March 2025

Research finds medical imaging experts see better in everyday life

Medical imaging experts are adept at solving common optical illusions, according to research from four UK universities.

The correct analysis of medical images from scans, such as MRI, is critical for diagnosing cancer and many other conditions.

A new study published today shows that people who do this professionally are also more accurate at judging the size of objects in common optical illusions.

In other words, medical imaging experts also literally see better in everyday life!

The research is also the first to show that people can be trained to do better at solving visual illusions, which was previously thought to be near-impossible.

"This is the first time that it’s been shown that people can be trained to do better at solving visual illusions. And they could perhaps even be used for training medical image analysts in future. "

Dr Radoslaw Wincza, from the School of Medicine and Dentistry

First author Dr Radoslaw Wincza, from the School of Medicine and Dentistry at University of Central Lancashire, said: “Many illusions are effective even if you know it is an illusion, and until now it was generally believed you could not train yourself to avoid the illusory effects.

“But this research suggests that training aimed at accurately perceiving objects in medical images has the effect of making experts less susceptible to visual illusions.

“This is the first time that it’s been shown that people can be trained to do better at solving visual illusions. And they could perhaps even be used for training medical image analysts in future.

“This is particularly important, given that 60 to 80 per cent of diagnostic errors are perceptual in nature,” he added.

Senior researcher Dr Martin Doherty, from UEA’s School of Psychology, said: “Optical illusions are designed to fool the brain. They can be a bit of fun, but they also help researchers shed light on how our brains works.

“We wanted to better understand whether people who are very experienced and skilled in visual recognition, do better at solving optical illusions.”

"Optical illusions are designed to fool the brain. They can be a bit of fun, but they also help researchers shed light on how our brains works."

Senior researcher Dr Martin Doherty from the University of East Anglia

Participants were shown a series of visual illusions that made it hard to correctly judge the size of two similar objects – and asked to identify the larger one.

The object size differences varied, giving the research team an estimate of how much participants’ judgements were affected by the illusions.Scientific Reports

They tested 44 radiographers and radiologists and compared their scores with a control group of 107 non-experts.

This research was a collaboration between the University of Central Lancashire, the University of East Anglia, Lancaster University and Cumbria University. It was funded by a British Academy/Leverhulme Small Grant.

Specific Visual Expertise Reduces Susceptibility to Visual Illusions is published in the journal Scientific Reports.

The images below show an Ebbinghaus illusion of relative size perception.

In this Ebbinghaus illusion of relative size perception, the orange circle on the left looks bigger than the one on the right - but it is actually 10 per cent smaller. In a new study, medical imaging experts were able to 'see through' the optical illusion. The research is the first to show that people can be trained to do better at solving visual illusions, which was previously thought to be near-impossible.

In each image the orange circle on the left is smaller than the orange circle on the right.

When the orange circle on the left is 6% smaller, most people see it as larger.

When the circle on the left is 10% smaller, most radiologists will recognise it as smaller.

When the circle on the left is 14% smaller, about half of non-radiologists now see it as smaller.

When the circle on the left is 18% smaller, most non-radiologists will finally realise it is smaller.

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An Ebbinghaus illusion of relative size perception01 / 04

When the orange circle on the left is 6% smaller, most people see it as larger.
When the orange circle on the left is 6% smaller, most people see it as larger.