...and that is why you are a left-brained user. 😉
Right brained ppl see the "whole picture", they see the picture as one object. Left brainers actually break it up into smaller chunks (subconsciously) and see it as a sum of those parts, it is not a single object.
The "default" spin you see when you first pull the picture up is what your brain orientation is... and that shadow plays a role in it. By dissecting the shadow itself (left-brain) you are not taking the perceived angle in 3-D space of the girl to the "floor" in to account etc... (or you are even dissecting those points further into smaller parts and removing much perspective) There is a host of ways to "see" this if you dissect each part, that is why it is a decent metric on how you think. Right-brainers just take the whole thing in and say "cool"... and probably start all kinds of thoughts on the girl and why she is spinning in mid-air. 😉
That is not saying one is better, just it points at different thinking processes.