The video my colleagues and I shot is amazing. A blind man is making his way down a long corridor strewn with boxes, chairs and other office paraphernalia. The man, known to the medical world as TN, has no idea the obstacles are there. And yet he avoids them all, here sidling carefully between a wastepaper basket and the wall, there going around a camera tripod, all without knowing he has made any special maneuvers. TN may be blind, but he has “blindsight”—the remarkable ability to respond to what his eyes can detect without knowing he can see anything at all. [To see the film of the experiment, go to www.ScientificAmerican.com/may2010/blindsight.]

TN’s blindness is of an extremely rare type, caused by two strokes he suffered in 2003. The strokes injured an area at the back of his brain called the primary visual cortex, first on his left hemisphere and five weeks later on the right. His eyes remained perfectly healthy, but with his visual cortex no longer receiving the incoming signals he became completely blind.

This article was originally published with the title Uncanny Sight in the Blind.

4 Comments

1. 1. reader2 08:58 AM 4/22/10

   The only comment I can give is that the film site is inaccessible.
   Will it be in the near future?

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2. 2. reader2 09:00 AM 4/22/10

   The film site is inaccessible. Is there a problem with site?

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3. 3. gcollins in reply to reader2 10:53 AM 4/22/10

   We're looking into it. In the meantime you can see the video by navigating to the blog posting at http://www.scientificamerican.com/blog/observations/

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4. 4. BC 08:10 AM 5/10/10

   When I visualise I don't actually see anything, it's a blank screen. However I can do maths in my head and I can get a sort of remembered image. I've wondered for a while now if I visualise with blindsight rather than normal sight. I'm interested in anyone's thoughts on this.

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