In fact, smiles and laughter were documented in many species, even as far as rats. As a humor researcher, I am quite surprised that psychoanalytical perspective is still common in regard to understanding laughter and humor. In fact, many studies have been conducted over the years to test his ideas and most of them didn't support it. Freud ignored completely the interpersonal use of humor which is how humor is used and laughter experienced in the majority of cases. He claimed that people who repress sexual and aggressive drives will enjoy humor more but the opposite is true. Humor also serve many other needs that Freud ignored.