The causes of congenital face blindness can be traced back to an early stage in the perceptual process, new findings reveal.

People with congenital prosopagnosia, or face blindness, are unable to use facial features to identify the person in front of them.

Until now, the cause of facial blindness was assumed to be associated with the later stages of the perceptual process.

These are the stages involved in converting facial information into abstract code for long-term storage.

"We were able to show that even the earliest face-selective responses, those recorded approximately 170 milliseconds after seeing a face, are altered in people with congenital prosopagnosia," said lead researcher Andreas Luschow from Charite hospital in Berlin.

"We were also able to show that these changes are closely linked to their deficit in recognizing faces," he added.

Results showed that even life-long contact with other people does not enable affected persons to compensate for this face recognition deficit.

This would suggest that the underlying neural mechanisms are divided into distinct, closed units, making it impossible for other areas of the brain to take over their function.

A better understanding of cognitive processes is not only important in the field of medicine, but also in other areas of research, such as robotics, where such knowledge may be able to provide 'biological inspiration' for the development and improvement of technological systems.

The findings were published in the journal PLOS ONE.