Color Visions and Philosophical Zombies

Illustration for article titled Color Visions and Philosophical Zombies

Ever heard of the philosophical zombie? It's a philosophical concept that rarely translates into physiology - until now. A case of false color-blindness makes us wonder: What's the difference between seeing something and knowing that you're seeing something?


Philosophical zombies are a matter of debate in the philosophical community. Start with the concept of a zombie, something that is dead inside, with no consciousness, just a mindless need to feed and a basic response to noise and movement. Now build it up a little. Maybe it shows minor instinctive responses in avoiding danger or getting around obstacles. Now perhaps it can make a few recognizable words, but they're just rote responses.

You get where this is going. Eventually, you can build a "zombie" up so it has no consciousness, but it physically responds the way a human does. It can hold a conversation, drive a car, do a job, and generally live out its days faking humanity. This is a philosophical zombie. It makes us question if there is a difference, tangible or intangible, between a sophisticated response and actual awareness.

That might seem like a purely theoretical distinction, but scientists seem to have found a (very limited) philosophical zombie. Although the patient in question, was able to make the right responses, he had no consciousness of what he was responding to.

The patient in question was recovering from a stroke, and one of his complaints was a loss of color vision. His medical providers noticed he wasn't making the same mistakes that many people with limited color vision do, and so they had him do a quick test. They showed different colors to him, and asked him to take a guess at what they were. He guessed right much of the time. They then asked how accurately he thought he was guessing. He gave an estimate of his accuracy, and that estimation shot up for the times when he guessed right.

So not only was this person seeing most colors, he knew, most of the time that he was seeing them. He just had no consciousness of the colors he was seeing. He was, in essence, a philosophical zombie when it came to color vision. Although he could behave as if he saw colors, he never, consciously did. So what do you think? Can you be a zombie, without anyone guessing that you are?

[Via The Achromatic Philosophical Zombie.]




Human consciousness most likely evolved as part of an increasingly sophisticated way of responding to the world. Consciousness is basically the ability to make a mental "model" of the world around you — and then include a model of your own self in that model of the world. This ability is just an extension of the intelligence that our ancestors evolved to deal with the world as successfully as possible — to notice patterns, make predictions, and thus increase the odds of survival. In other words, it's just a form of "sophisticated response."

The upshot is that on the one hand, making a hard distinction between "sophisticated response" and actual "awareness" seems a bit artificial — the latter is really just an extra-complex, expanded form of the former. On the other hand, our society was built by people who evolved their "responses" to the point of self-awareness, so I don't think an entity that lacked awareness could function smoothly in our world. A philosophical zombie might be able to handle many daily tasks, but sooner or later, some need for a complex interaction would arise where a lack of ability to respond with the same sophistication as the average human would stand out clearly. Evolution doesn't like waste, after all — we wouldn't develop consciousness, and then waste it. We use our ability to mentally model the world, and ourselves, on a regular basis, and the absence of such an ability would be missed, sooner or later.