Blindsight: weird phenomenon deepens the mystery of consciousness

Blindsight is a strange phenomenon that sometimes occurs when people have lost sight due to visual cortex damage but still respond to visual stimuli outside of their conscious awareness. New research into blindsight is offering clues, and even more riddles, about how we can "pay attention" outside of what we historically have considered conscious thought. From David Robson's fascinating article in BBC Future:

One of the first tasks (in a recent research effort) was to test exactly what blindsight patients are capable of without their conscious visual awareness – and the results have been quite remarkable. Of particular interest has been the fact that they can sense emotion: when presented with faces, they can tell whether it is happy or sad, angry or surprised, and they even start to unconsciously mimic the expressions. "Even though they did not report anything at a conscious level, we could show a change in attitude, a synchronisation of emotional expressions to the pictures in their blind field," says (Tilburg University scientist Marco) Tamietto…

Besides mirroring expressions, they also show physiological signs of stress when they see a picture of a frightened face…

In 2008, Tamietto and (blindsight research pioneer Lawrence) Weiskrantz's team put another blindsight patient through the most gruelling test yet… He was blind across the whole of his visual field, and normally walked with a white cane. But the team took away his cane and then loaded a corridor with furniture that might potentially trip him up, before asking him make his way to the other side. "Despite saying he wasn't able to see, we saw him shooting by on his very first attempt," says Tamietto. You can watch it for yourself, on the video below.

Importantly, the participant claimed that not only was he not aware of having seen anything; he was not even aware of having moved out of the way of the objects. He insisted he had just walked straight down the hallway. According to Beatrice de Gelder, who led the work, he was "at a loss to explain or even describe his actions".

"Blindsight: The strangest form of consciousness" (BBC)