For the purpose of this study, the following terms are defined:
* Monogamy: exclusive sexual relationships between partners.
* Mate: a partner in a legal marriage or a committed primary relationship with or without legal marriage.
* Extra-monogamous sex (EMS): coital activity between two partners, at least one of whom currently describes his or herself as exclusively committed to a primary relationship with another person, with or without legal marriage.
* Extramarital sex: coital activity between two partners, at least one of whom is legally married to someone else.
* Comarital sex (CMS): coital activity between two partners not married to each other with the knowledge and participation of one or both mates. (Behavior commonly grouped under this heading includes swinging and mate-swapping.)
* Consensual sex: coital...