I recently read a thread about men Vs women eating differently in general not a rule. Specifically, the way men crunch their crisps more and tend to tilt their head back to pour the final contents in, like a cement mixer 
Since reading that thread I swear every male I've seen eating a bag of crisps in public has done exactly that, and yet I've not seen a single woman do it at all.
AIBU to wonder what's behind this? Why on earth has this general difference developed? Am I the only one disturbed by such a trivial but key difference?!