Some people may engage in swinging to add variety into their otherwise conventional sex lives or due to their curiosity.
Research on swinging has been conducted in the United States since the late 1960s.
One 2000 study, based on an Internet questionnaire addressed to visitors of swinger-related sites, found swingers are happier in their relationships than the norm.
Opponents are also concerned about the risk of pregnancy and STIs such as HIV, arguing that even protected sex is risky given that some STIs may be spread regardless of the use of condoms, such as Herpes and HPV.
In a 1992 study, an overall 7% of swingers had quit swinging because of the HIV/AIDS epidemic.
Swingers rate themselves happier ("very happy": 59% of swingers compared to 32% of non-swingers) and their lives more "exciting" (76% of swingers compared to 54% of non-swingers) than non-swingers, by significantly large margins.
There was no significant difference between responses of men and women, although more males (70%) than females completed the survey.
Most religious communities and moralists regard swinging as adultery, not withstanding that it is with the knowledge, consent or encouragement of one spouse to the other.
Some argue that strict monogamy is the ideal form for marital relationships and that sexual relations should only take place between marriage partners or, perhaps, between partners in a committed monogamous relationship.
60% said that swinging improved their relationship; 1.7% said swinging made their relationship less happy.