Friday, January 26, 2007

Echolocation and Knowledge

Wednesday I argued that you can probably echolocate considerably better than you think you can. Let me amplify on that idea.

First, we not only have the capacity to echolocate, but we do actually use echolocatory information in negotiating through our daily environment. Our sense of the space we're in and the objects that surround us is continually confirmed or altered by echolocatory information. Here's an example Mike Gordon and I used in our 2000 essay on human echolocation: Wenger Corporation's "virtual room" can electronically simulate the acoustics of a very large room within a small space. According to Mike, when unsuspecting listeners walk into such a room, they quickly sense that something is amiss. Typically, they glance upward at the ceiling to see if it is unusually high. Now that I'm attuned to it, I'm struck by the acoustic difference between the typical classroom and a carpeted room with lots of soft furniture. If I'm thinking of it as I walk through a doorway, I notice the acoustic transition between rooms and the echolocatory sense I have of the doorframe as it passes near my ears. Even if I weren't thinking about it, a classroom that sounded like a living room or a doorway that gave me no echolocatory sense of its frame, would likely disconcert me -- you, too, I'd wager, independent of any intellectual apprehension you have, or not, of your capacities for echolocation.

Second, there's something it's like to echolocate. It's not an entirely nonconscious capacity. We have auditory experience of the direction and distance (and maybe also the texture and shape) of silent objects. This experience is both ordinary and pervasive.

Yet, despite the two points above, we have very little apprehension of this experience. For example, in the 18th and 19th centuries, blind people who navigated by echolocation were struck by their remarkable ability to avoid unseen objects in novel environments -- and many of them hypothesized that they did so by feeling pressure on their faces. In fact, the capacity was generally known as "facial vision". Yet, 20th-century researchers established that this was an auditory, not a tactile capacity (for example, by covering their faces and not their ears and vice versa). Most normally sighted subjects who participate in echolocatory experiments (as Mike and Larry and others have noted, and as I have seen informally) are surprised at the results, and many have the impulse to think they are feeling pressure on their faces.

If we assume -- as I think is probably warranted -- that echolocatory information is not generally felt as pressure on the face, then these people have gone wrong about a pervasive and fundamental aspect of their ongoing conscious experience; and most of us, even if not wrong in quite that way, are strikingly ignorant about this aspect of our stream of experience.

We should, I think, turn the epistemology of Locke and Descartes on its head: What we know best and most directly are outward objects (the size of the room, the shape of the desk before me); what we know only partially, tentatively, and after reflection is our sensory experience of that world.


Anonymous said...

Knowledge of the experienced world and knowledge our sensory experience is a distinction that perplexes me; perhaps phenomenology is simply less suited--or 'designed'-- to track itself. The facial metaphor for describing echolocation must be a fascinating example of something like this, as well as our colorful emotions.

It might be interesting to note here that recording engineers, with the help of equipment designed by acoustic engineers, master the subtle differences created by echo effects (even simple processors allow you to change what “kind of room” you are recording in), and combining this with stereo and frequency modulation, they create most of the more aesthetically pleasing differences in music we listen to (e.g. reverb, chorusing, flanging). From what I recall, every track on a recording has its own simulated acoustic environment, with echo as the primary building block. Some of the most objective aesthetic differences we perceive in our environment would seem to come from this kind of auditory perception. . . .

Clark Goble said...

It's actually interesting how we're discovering that humans do have a lot of senses that other mammals have which we thought we didn't. Your example of the room and echolocation is an excellent one. There was a study about humans emulating bloodhounds in New Scientist this week as well. The old experiments regarding putting male pheremones on bathroom stalls and seeing which ones men go in is an obvious one as well.

I think part of the problem is that while we have, to varying degrees, these senses we don't have them in an obvious fashion in our conscious awareness. So people discount them. One could always wonder if bats have them in conscious awareness as well.

Anonymous said...

Hi Eric,

Though I think that you are right with your conclusion that the sensory experience shouldn't be taken as some kind of given, I'm not sure that this case gives conclusive evidence in that direction (and I guess you are aware of that because you said "probably").
There are two possibilities which I can think of:
This might be a case of synaesthesia that we all have, and that maybe those people really feel pressure on their faces.
Or it might be completely different sensory experience, but because it is not easily distinguished, not having a concept for it, people are describing by the closest sensory experience they have - the tactile one.

Fido the Yak said...

If I were to summarize, I'd say we have a firmer grasp on the objects of experience than we do on the manner of experience. Does uncertainty about the latter mean that we are uncertain about whether or not we have an experience?

Eric Schwitzgebel said...

Thanks for all the comments, folks. For a change, I think I agree almost entirely with them!

To answer your question, Mr. Yak (or do you prefer "Fido"?): My skepticism doesn't generally penetrate so far as to think that we can go wrong about whether we are having any experience at all (as opposed to no experience whatsoever). But I do think we can doubt (and be mistaken about) whether we are having sensory visual experience (as opposed to visual imagery, see Perky 1910!) or tactile experience (as opposed to auditory).

Fido the Yak said...

Fido is fine, or Mr. Yak if you're more comfortable with honorifics.

You know what I am getting at is whether you're really turning Descartes on his head. Let me give an example just to be clear. Let's say I have an experience of being in a large room. Possibly Wenger Corp engineers and assorted demons with pixels have conspired to create an illusion of me being in a large room while I'm actually in a small booth. What I am certain of is that I have an experience of being in a large room. Does my ignorance or fuzziness about echolocation alter what I know for certain, that I have an experience of being in large a room?

Eric Schwitzgebel said...

I think there are cases in which we know our experience better, cases in which we know the outside world better.

Let me reverse your example: Someone who doesn't know about echolocation, who is after a bit of reflection inclined to deny that she can auditorially detect the size of a room except perhaps in unusual conditions and extreme cases, might be quite right about the external world (that she's in a small room) and quite wrong about her auditory experience (of the distance of the walls).

As a general rule, I'd say we know more about ordinary, middle sized dry goods than we know about our sensory experiences of middle sized dry goods. A demon could deceive me about the outside world, but I also think a demon could fiddle with my brain to produce the judgment "I'm having a visual experience of redness" when I'm actually having no such experience.

So I stand by my claim that Descartes got things (approximately) backwards.

Anonymous said...

When I was a small child I liked to walk around with a mirror held out in front of me, and step over the lintels of the doorways. I would ask my mother to come into the living room, and say, "come in here and see how upside down I am."