Animals, or at least most mammals and birds, can be trained. Human animals that haven't been trained with a morality system or something effectively similar have only a relatively straight-forward cost/benefit analysis as their decision calculus.

Most humans have a morality system to the extent that they'd rather starve to death than engage in cannibalism, for example. It requires more effort, but they can also be socialized to endure reduced access to drugs in exchange for not stealing.