I would walk the dog with my grandson and would prep a poop bag to pick up waste, and he was transfixed so I showed him how to find the top side, part the sides and put it over the hand in preparation for use.

And he was happy to wear a poop bag on his hand, which creeped out granny, even though the bag never actually touched dog poop.

Soon after that it was clear that he discovered (or was trained) to recognize feces is yucky and to be avoided. (he was never in close smelling distance to the dog poop, so he got this from elsewhere.