three-dimensional navigation

When we navigate through our environment, do we track mostly in two dimensions or in three? Clearly, we can move in all three dimensions, but does our internal map relate to the vertical direction in the same way as it does to the horizontal axes on the ground? That question has not yet been definitively answered, but recent research on flying bats shows us what three-dimensional navigation looks like in the brain. It turns out that fruit bats also mostly navigate in two dimensions, since quite a bit of their flying time involves getting from their caves straight to their favorite fruit…