Fifty-eight Moso people and 61 Han people participated in Experiment 1. A 2 Ethnicity (Moso vs. Han) × 2 Gender (Male vs. Female) × 4 Relationship Type (Kin, Azhu/Lover, Friend, Stranger) mixed design was used. The participants’ emotional responses were rated in a Likert scale after imaging sexual intercourse with the four heterosexual relationship types respectively. Results in Experiment 1 showed that there was a remarkable ethnicity difference in incest avoidance. The Han people expressed a much stronger sense of disgust than the Moso people to sexual behavior with kin, while there were no significant differences in the degree of disgust caused by sexual behavior with non-kin between the Hans and the Mosos. The emotional responses caused by imaging sexual behavior with special objects differed between the two genders. Female participants’ negative emotions (including disgust) were much stronger than those of male participants’, while those of positive emotions (including romantic) were exactly the opposite. However, this kind of gender differences was non-significant regarding kinship.

Fifty Moso people and 98 Han people participated in Experiment 2. The design was similar to Experiment 1. A Likert scale was used to evaluate the participants’ willingness to perform an altruistic behavior to help a kin, azhu/lover, friend, and stranger respectively. The results indicated that the Moso people were more willing to perform selfless altruistic behaviors than the Han people to a kin, a friend or a stranger. However, the situation was the opposite when the azhu/lover was in danger. The differences were smaller among the Han people when rating the altruistic behaviors between kins versus those between lovers, while the differences were larger among the Moso people when rating the altruistic behaviors between kins versus those between azhus; The differences were smaller among the Moso people when rating the altruistic behaviors between azhus versus those between friends, while the differences were larger among the Han people when rating the altruistic behaviors between lovers and those between friends. There was a significant gender difference between the Hans and the Mosos towards the willingness to help their azhu/lover. Han males had a stronger willingness to perform altruistic behaviors than Han females, whereas Moso females had a stronger willingness to help their azhu than Moso males.

In general, the results in the current study showed that the Han people treated their lovers as kins while Moso people treated their azhus as friends on the psychological and behavioral level. The nature of the azhu relationship under the sexual union in the Moso society was a kind of non-kin friendship, which was fundamentally different from the couple relationship of mainstream society.