The vestibular system can detect whether you look up or down. It could be that the reflex triggers when you a) look down (vestibular system) and b) have a visual parallax that indicates depth (visual system).
Should be easy to test by closing one eye. Alternatively, it is the degree of accommodation of the lens. That should be testable by looking down with a lens that forces accommodation on short distances.
The negative should also be testable by asking congenitally blind people about their experience with this feeling of dizziness close to a rim.
I think I would feel characteristic innate-fear-of-heights sensations (fear + tingly sensation for me, YMMV) if I were standing on an opaque bridge over a chasm, especially if the wood is cracking and about to break. Or if I were near the edge of a roof with no railings, but couldn’t actually see down.
Neither of these claims is straightforward rock-solid proof that the thing you said is wrong, because there’s a possible elaboration of what you said that starts with “looking down” as ground truth and then generalizes that ground truth via pattern-matching / learning algorithm—but I still think that elaborated story doesn’t hang together when you work through it in detail, and that my “innate ‘center of spatial attention’ constantly darting around local 3D space” story is much better.
There are likely multiple detectors of risk of falling. Being on shaky ground is for sure one. In amusement parks, there are sometimes thingies that share and wobble and can also give these kind of feeling. Also, it could be a learned (prediction by the thought assessor) reaction, as you mention too.
The vestibular system can detect whether you look up or down. It could be that the reflex triggers when you a) look down (vestibular system) and b) have a visual parallax that indicates depth (visual system).
Should be easy to test by closing one eye. Alternatively, it is the degree of accommodation of the lens. That should be testable by looking down with a lens that forces accommodation on short distances.
The negative should also be testable by asking congenitally blind people about their experience with this feeling of dizziness close to a rim.
I think I would feel characteristic innate-fear-of-heights sensations (fear + tingly sensation for me, YMMV) if I were standing on an opaque bridge over a chasm, especially if the wood is cracking and about to break. Or if I were near the edge of a roof with no railings, but couldn’t actually see down.
Neither of these claims is straightforward rock-solid proof that the thing you said is wrong, because there’s a possible elaboration of what you said that starts with “looking down” as ground truth and then generalizes that ground truth via pattern-matching / learning algorithm—but I still think that elaborated story doesn’t hang together when you work through it in detail, and that my “innate ‘center of spatial attention’ constantly darting around local 3D space” story is much better.
There are likely multiple detectors of risk of falling. Being on shaky ground is for sure one. In amusement parks, there are sometimes thingies that share and wobble and can also give these kind of feeling. Also, it could be a learned (prediction by the thought assessor) reaction, as you mention too.