While I haven't thought much in the past about "gravity traps", at least not enough to give it a cool name, I can certainly say I've experienced the effect. I love canyon hiking, and a couple of times have found myself at a very dangerous precipice after spending quite a bit of time bushwhacking down brush and boulder-filled canyons "for fun". It is a hypnotic phenomenon, fueled by your own ego and over-whelming sense that, most likely, nothing will go wrong, and you can deal with whatever obstacle you encounter, including deep, precipitous drop-offs. You feel this way right up until the moment that your a_s is in a sling cuz you've overestimated your abilities and have fallen, broken something, or whatever.

I have to say that, as I've gotten older (and slower), I at least am able to anticipate this predicament, and realize that even snail's-pace traveling will eventually get me back up to a safer spot, which is how I now tend to hike anyway. You miss a lot less that way.

Oh, and I rarely hike DOWN canyons anymore. It's a lot safer (IMHO) to hike UP them.