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.