How old is yours? Mine is nearly 4 and has figured it out. It helped that, when we went on vacation, the supermarket sold complete chicken with the head and feet still attached, and cow tongues and pork feet and things. We even pointed out a pig brain for him to look at. It also may have helped that is favourite food is snails, mussles, squid and small fish with their heads attached (fried anchovies, he calls them eye fishies). All pretty recognisable on a plate!