I read about a study where they found that people noticed moving animals faster than equally large moving cars. (I could look up the source if anyone is interested.) For your point 3: As far as I recall this effect did not seem to rely on whether those people grew up with animals (African subjects) or not (American subjects).

Perhaps if you would find some other task for your volunteers to test you learn/unlearn hypothesis with. Some task that we do not suspect of being hard wired into our brain. But a task people would nevertheless encounter at an early age.

Anyway - thanks for reading through my amateurish ideas.