> Chickens are very sweet animals, and are quite intelligent.

They did tests on chickens, and apparently they understand the concept of showing restraint on a current action, with the view on having a larger reward later.

Something along the lines of: "If you don't eat these grains now, we'll reward you with twice as many grains later".

That's something that dogs can't do, for instance.

Maybe the dog just values immediate reward higher even though it understands it could get even more later? How would you control for that?