It would be better to test behavior that is wrong by almost any standard, including that of their own species. The Austrian ethologist Konrad Lorenz gave one of my favorite examples, about his dog, Bully, who broke the fundamental rule never to bite your superior.

Humans don’t need to teach this rule, and indeed Bully had never been punished for it. The dog bit his master’s hand when Dr. Lorenz tried to break up a dogfight. Even though Dr. Lorenz petted him right away, Bully suffered a complete nervous breakdown. For days, he was virtually paralyzed and ignored his food. He would lie on the rug breathing shallowly, occasionally interrupted by a deep sigh. He had violated a natural taboo, which among ancestral canines could have had the worst imaginable consequences, such as expulsion from the pack.

Among the primates, the most suggestive cases of remorse concern bonobos. These apes are as close to us as chimpanzees, but far more peaceful and gentle, which means that they almost never hurt one another. Whereas in most primates reconciliation after a fight is typically sought by the subordinate party, in bonobos it is the dominant animal that seeks to make amends, especially if he has inflicted an injury. He may return to his victim and unerringly reach for the exact same toe that he has bitten and carefully inspect the damage. He obviously knows precisely what he has done and where. Then he spends half an hour or more licking and cleaning the wound that he himself inflicted.

Another human emotion that has been elevated to a special status is disgust. In his book “Human: The Science Behind What Makes Us Unique,” the neuroscientist Michael Gazzaniga views disgust as one of the five emotional modules that set us apart from all other animals. Here, too, dogs are a prime example, given that they eat feces and lick their testicles. This is taken as proof that dogs must lack disgust. But give your dog a cut lemon (not recommended) and you will see a full-blown yuck! response with curled-up lips, drooling and withdrawal from the sour smell.

Disgust is an incredibly adaptive response. Every organism needs to avoid parasites and prevent the ingestion of harmful foods (citrus fruits can be poisonous to canines). Ignoring this mundane origin, however, psychologists have fallen in love with the moral connotations of this emotion. We are disgusted, for example, by someone who fakes a racist attack on himself to gain positive media attention. We “turn up our noses” at such people, showing our typical disgust face with wrinkled nose and narrowed eyes.

But even if moral disgust is special, it is no accident that our facial expression also blocks wafts of foul air from getting into our eyes and nostrils. This hints at the emotion’s origin. Chimpanzees show the same expression when it rains, something they hate. As soon as a downpour starts, young and old pull an ugly face known as the “rain face,” in which they bring their upper lip close to their nose and stick out their lower lip.