A man who was left completely blind by multiple strokes has been able to navigate an obstacle course using only his “sense” of where hazards lie.
The feat is an example of “blindsight”, the ability of some blind people to sense things that they cannot see.
Scientists already knew that the man, known only as TN, reacted to facial expressions that he could not see.
Brain scans showed that he could recognise expressions including fear, anger and joy in other people.
However, he is totally blind and normally walks using a stick to alert himself to objects in his path.
To test the extend of his blindsight, scientists constructed an obstacle course made up of boxes and chairs arranged in a random pattern.
Not only was TN able to safely manoeuvre the course he did not bump into a single box or chair.
Professor Beatrice de Gelder, from the University of Tilburg in the Netherlands, who led the study, said: “This is absolutely the first study of this ability in humans.
“We see what humans can do, even with no awareness of seeing or any intentional avoidance of obstacles. It shows us the importance of these evolutionary ancient visual paths. “They contribute more than we think they do for us to function in the real world.”
Experts believe that blindsight trades on our subconscious ability to recognise things we cannot see.
They think that even though the eyes do not identify objects something in the brain can still respond to what they see on a subconscious level.
Earlier studies had shown a similar ability in monkeys with brain injuries.
The findings of the study were published in the journal Current Biology.
By Kate Devlin, Medical Correspondent
Last Updated: 10:20AM GMT 23 Dec 2008
Source: The Telegraph