November 23, 2004


I just read an article in the NY Times about devices that translate one type of stimulus to another. For example, one of the devices translates visual input from a video camera to tactile stimulus on the user's tongue. And the user can "see", at least to some degree. Another guy who has no feeling in his hands was able to feel once again by using a special glove and some sort of stimulus device on his forehead.

What's especially interesting in the latter case is that the guy claims that the sensation was as though it was from his fingertips. On the BrainPort web site, there are some some video clips of a blind guy learning to use the video camera-tongue thing. His perceptions seem to be somewhere between mentally translating tactile sensations and "real" vision. This is a grown adult (who was able to see) learning to do this. I'd bet that a newborn baby with one of these things would be able to function very naturally in the world -- I'll have to restrict myself to talking about how people behave and report the sensation, because, not having experienced it, I have no idea how to talk about "what it's like."

I find this totally fascinating and tremendously relevant to philosophy of mind -- when I told my roommate Jonathan about this, he looked at me for a moment and then said, "I want to know what it's like to be a bat."

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Blogger Dub! said...

Dennett discusses a prosthetic vision experiment really similar to this one in Consciousness Explained (p. 338). Blind subjects were given a pair of glasses that translated a video image of the scene ahead of them into a matrix of tingles on the subject's back or belly. After they got used to the instrument, the tactile feeling just dropped out of the picture, and the experiece of things in front of them just became transparent.

The question Dennett addresses is whether these subjects are actually having visual expriences as the rest of us do. He is sympathetic with a functionalist characterization of experience (as am I); if the subjects behave the same way towards the world as we do, they they have the same visual experiences.

The problem is that their behavior didn't quite synch up. For instance, the experimenters showed some blind college kids who were hooked up to this device some Playboy pictures, and the boys weren't aroused. (The boys were understandably disappointed.) There are a number of possible explanations for their lack of affect - maybe the image resolution was just too low for any arousal mechanisms to kick in (if you look at a chunky and pixellated picture of a naked woman, it would take a lot of imagination to get turned on). Another possibility is that we have deep-seated modules for arousal in the reptilian portions of our brain, and it's wired in a very specific way to inputs from our retinas - tactile simulation just can't get the module to fire in the right way. I'm not especially sympathetic to this view (I think there's more plasticity to the brain than that would suggest), but it's certainly a possible explantion for their lack of affect.

It looks like these new experiments involving tactile inputs on the tongue might have a higher resolution than the old belly/back stimuli that Dennett wrote about. I wonder if the blind guys hooked up to this thing get turned on by pornography?

11/25/2004 04:20:00 PM  
Blogger Tucker said...

Winston, do you have the date of that article. I would like to find it and copy it.

As for what it's like to be a bat, couldn't they hook the think up to sonar imaging? I wonder if it should turn out that what it's like to be a bat isn't all that different from what it's like to see as we do.

What I would really be interested in is the electromagnetic sense found in some sharks. I read about some species of sharks that troll along the bottom of the ocean and use electromagnetic feedback to locate fish. They have this in addition to vision.

11/30/2004 08:28:00 AM  

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