| 1) People, especially kids, jump between and across structures all the time. 2) Humans are great at throwing and catching objects, even with complex, changing trajectories--bouncing off walls, etc. 3) We have two innate senses that are clearly adapted to 3 dimensions: stereoscopic vision and proprioception. What makes those behaviors relatively intuitive is constant acceleration. In a sense constant acceleration makes everything 2D. (Or 2.5D?) When humans need to track objects which independently accelerate along 3 axes, then there's a much stronger case for an environment alien to humans. (Counter point: hunting birds, though I believe hunters prefer to take their shot when birds are beginning or ending their flight. But notably the most salient characteristic there is acceleration, not merely relative movement in 3D space.) Yeah, the more that I think about it, you get much more predictive power by emphasizing acceleration, not spatial dimensionality. And I don't think that's being pedantic; the distinction matters. When you look at studies of how the brain processes motion, constant acceleration (at least along 2 of 3 axes, unless/until hitting another object) is often one of the key assumptions that seems to be built into our cognition. For example, tracking many objects moving independently in 3D space is pretty darned difficult for humans.[citation needed] But that probably has more to do with relative motion (and thus relative acceleration) than with the number of dimensions as a human can track two such objects surprisingly well, especially if they have a third, fixed reference independent from themselves. Would be curious to compare & contrast studies of spatial cognition between marine animals and terrestrial animals, though. |