New test of face perception

Prosopagnosia, also known as face blindness, is when people can’t easily recognise differences between faces. As many as 3 in every 100 people have the condition and are at risk of social embarrassment, social isolation, anxiety and depression. People with the condition have reported being labelled ‘rude’ or ‘aloof’ by co-workers because they fail to recognise them. Even more distressingly, some mothers with the conditions have reported that they have difficulties recognising their children in the school playground.

Lead on the project, Dr Andrew Logan, from the University of Bradford's School of Optometry and Vision Science, explains: “For most of us, a brief glimpse of a face is enough to judge someone’s age, gender, ethnic background and to know whether or not that face is familiar. That we are so good at discriminating between faces is actually quite remarkable. After all, to a first approximation all faces are the same: two eyes, above a nose, above a mouth. Our visual system has evolved, however, to be very sensitive to subtle differences between faces and we are extremely accurate at recognising faces that are familiar to us.

“For some people, however, discriminating between faces is not so easy.”

Although treatments for the condition are not currently available, it is important for healthcare workers to be able to identify people with prosopagnosia so that support can be put in place to assist the patient.

Dr Logan has been working with colleagues from Glasgow Caledonian University and York University, Toronto on a new test of face perception.

The new test involves presenting participants with four faces and asking them to identify the odd one out (the face that differs from the others). The test uses simplified face images, synthesised from real face photographs. Synthetic faces can be very precisely modified, enabling the task to be made easier or harder to match the face discrimination ability of individual patients.

The team tested 52 young adults with no known difficulties with face perception. They found a broad range of face discrimination thresholds, with some highly sensitive to small face differences and others needing much larger differences for reliable discrimination. When repeating the test, they found it was highly reliable and repeatable.

They also tested a patient who reported lifelong difficulties with face recognition. This patient’s test results were substantially outside the normal range (more than 7 standard deviations). In comparison, the same patient was just outside of the normal range of ability on two existing tests of face perception (2 standard deviations).

Dr Logan said: “Some existing tests are unable to measure the whole spectrum of face perception ability. In addition, some tests don’t exclude the possibility of other visual or cognitive problems, e.g. poor memory. Our results show that the test is very reliable and can be performed in less than four minutes, making it suitable for clinicians to use.”

Working with Dr Logan on the development of the new test are Dr Gael Gordon and Professor Gunter Loffler from the Department of Life Sciences at Glasgow Caledonian University and Professors Frances Wilkinson and Hugh Wilson from the Centre for Vision Research at York University, Toronto, Canada.

Image shows the test with an easy example on the left, (approximately 95% of typical adults would recognise the ‘odd’ face) and a harder example on the right (only 1 in 4 typical adults is expected to be able to spot the difference).

The original article is available on ScienceDirect at http://www.sciencedirect.com/science/article/pii/S0042698915003624