why?

Coming out of the holiday candy fest with a determination to feed my children something other than candy and cookies for breakfast, I got into a serious power struggle with Gavin over a banana. He was sure that if he ate it he would die a horrible death from banana poisoning(0r maybe from the sheer healthiness of if). After a prolonged struggle I won(I'm bigger, stronger, and doggone it you're going to eat this banana). Off to play outside woo hoo. Then the great question...why...oh why is it such a struggle to eat one little banana(or anything else I fix for meals)...but then it is an irresistible compulsion to eat/slurp/revel in dirt/mud? These photos were taken within an hour of said power struggle.