Zombie Vison

Visual perception is an important part of our conscious experience. For us visual people, it's almost impossible to imagine "being conscious" of the surrounding world without a nice, colorful image. We might be used to the notion of subconscious thoughts, but being able to respond to visual stimuli without realizing it is a very counterintuitive idea.

 Actually, there are people who are able to process visual information (to some extent) even though they think they are completely blind to one half of visual field. This rare condition is called blindsight and occurs in patients suffering from cortical blindness, which means nothing is wrong with the eyes or optical nerves and the damage occurs in part of their cortex that is concerned with processing visual information. These patients can tell apart simple stimuli presented in the "blind" part of the field when confronted with forced-answer questions, but they will admit they´re only guessing. Even more surprising is that they can even discriminate between colors while completely lacking any subjective experience of "redness" or "blueness".



 This might remind one of extra-sensory perception, but as creepy as it is, there is probably nothing parapsychological about blindsight. It seems the information might be processed in the subcortical areas of the brain or shipped directly to secondary visual areas surrounding the primary visual cortex. Thus, sense is made of the information without producing conscious experience. Which takes us back to consciousness - if important information can be abstracted without consciousness, why bother with it?

There appear to be many systems in our body, like adjusting bodily posture based on vestibular cues, that operate without conscious control. Even if we eventually realize they did something, it's only an observation of their behavior, not direct conscious insight into their workings.  In this interesting paper, Koch & Crick call them on-line systems or zombie agents*. "Zombie" as in not possessing consciousness, "on-line" as in processing information quickly and in direct response to the changing environment. From this definition, a possible explanation emerges - this kind of processing might be sufficient only for simple forms of action, like not bumping into things in our environment, while for complex manipulation with concepts the truly human thinking is based on, we need conscious representations. Moreover, since this kind of zombie-like vision only occurs when the brain is damaged, it's probably not very healthy, just like the popular view of zombies suggests.

Ramachandran on blindsight

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* -  zombie in this case means a creature indistinguishable from human in it's action, but one that doesn't possess consciousness