Saturday, January 19, 2013

Pill Goggles: The Consequences of Oral Contraceptive Use During Mate Choice

There is a well-established bias, in humans and other mammals, to select mates who are genetically dissimilar at the major histocompatibility complex (MHC). This bias is thought to be the result of preferences for body odor expressed during mate selection. It is also known that oral contraceptive (OC) use by women reduces or reverses this bias, with the result that couples who meet when the woman is on the pill will be more MHC-similar. MHC-similarity has a downside: women in these relationships report reduced sexual satisfaction with their partner and increased interest in other men.

This raises an interesting question: what are the consequences for a relationship that started during OC use when, later in the relationship, the woman quits the pill?

One possibility is that with his MHC-similarity now exposed to her nose, she becomes less satisfied with her partner and the relationship suffers. On the other hand, OC users tend to prefer men with high parental investment traits such as wealth and intelligence, rather than guys with studly masculine traits like a strong chin and dominant behavior (also associated with higher unfaithfulness to partner). So it could be argued that a woman who chooses her partner while on the pill is more likely to remain satisfied with the relationship.

Untangling these possibilities is clearly not something that can be done experimentally. The best approach is to survey large numbers of women regarding various aspects of their relationships. S. Craig Roberts and his research team did this, selecting for study women who had at least one child in the relationship. (This roughly standardized for relationship commitment and guaranteed that women who had been on the pill at the time of mate choice experienced a change in hormone profile when they quit it to become pregnant.)

The researchers surveyed 2,519 women, of whom about 40% were OC users when their relationship was formed; the other 60% were non-users. Among women in currently ongoing relationships (about 70% of the total), the results were striking:
Women who used OC during partner choice (compared with non-users) scored lower on sexual arousal with their partner, on satisfaction with his sexual adventurousness, and on sexual proceptivity and attraction towards him. They also rated their partner’s body lower in attractiveness compared with non-users. By contrast, these women appeared more satisfied with general (nonsexual) aspects of their partner: they were significantly more satisfied with his financial provision compared with women who were not using OC during partner choice.
Even after statistically controlling for several factors unrelated to OC use and mate choice, the main effects remained: OC use at time of partner choice was associated with lower sexual satisfaction and with finding their partner less attractive. Similar results were found for retrospective ratings of ex-partners. When it comes to ending a relationship, women who used OC during partner choice were less likely to split up than were women not using OC. However, when a split did happen, it was more likely to be made by the woman if she was an OC user at the beginning, than if she were not. Interestingly, women who were OC users during partner choice “were more satisfied with non-sexual aspects of their relationship, including the partner’s financial provision.”

Where does all this leave us with respect to our initial questions?

As the authors put it, “a woman’s use of OC at the time when she meets her partner has measurable downstream consequences for partnership outcome.” The results are consistent with the hypothesis that OC use interferes with smell-based adaptive preferences for MHC-dissimilar men: OC users run a greater risk of sexually unsatisfying relationships in the long run. Yet to the extent that OC users tend to select men on the basis of being good providers rather than studly, pill use might increase the odds of successful long-term relationships. One way or another, pill goggles affect how a relationship plays out in the long run

The study discussed here is “Relationship satisfaction and outcome in women who meet their partner while using oral contraception,” by S. Craig Roberts, Kateřina Klapilová, Anthony C. Little, Robert P. Burriss, Benedict C. Jones, Lisa M. DeBruine, Marion Petrie, and Jan Havlícek, published in Proceedings of the Royal Society: Biological Sciences 279:1430-1436, 2012.

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