Face-blind people can distinguish shapes: Study

People who are unable to recognise faces owing to face blindness following brain damage can still learn to distinguish between other types of very similar objects, researchers said.

Prosopagnosia, or face blindness following brain damage renders people unable to recognise and distinguish between faces - in some cases, even those of their own family members.

The finding provides fresh support for the idea that the brain mechanisms that process face images are specialised for that task.

"It also offers evidence against an 'expertise' hypothesis, in which the same mechanisms are responsible for recognition of faces and other highly similar objects we have learned to tell apart," said Constantin Rezlescu, a psychologist at Harvard University in Cambridge, Massachusetts.

The team trained two volunteers to recognize greebles - computer-generated objects that differ from one another in similar ways to faces.

The two volunteers spent eight training sessions of up to one hour learning to recognise 20 different greebles.

By the end of the training, they could tell individual greebles apart just as quickly - a sign that they had become experts in recognising them.

The training also enabled the volunteers identify individual greebles with the same ease as volunteers without face blindness who underwent the same training.

"The paper refutes a core prediction of the expertise hypothesis that a brain injury which severely damages face recognition should make it impossible for someone to become very good at telling apart individual members of any other category," Elinor McKone, a psychologist at the Australian National University in Canberra, told the Nature.

Rezlescu now plans to search for bird watchers, dog trainers and people with other such skills in a database of about 9,000 people who say they have had prosopagnosia from birth.

The study appeared in the journal Proceedings of the National Academy of Sciences1.