Bingowings said:

This doesn't happen until sometime in the toddler stage, usually around the time the baby is on solid food and can make very basic gestures indicating preference.

And how would you decide what constitutes a preference and what a gesture indicating that is? My baby brother, ever since he was about two months old (at least), has preferred lying on his right side as opposed to his left, and would sometimes cry when lain on the wrong side. Why is that type of preference different than a toddler pushing away food he doesn't like, or complaining about it?