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It has been reported (and repeated) several times that women who use the typical birth control pill (with both estrogen and progestin) show different preferences for men, depending on whether they are currently using the pill or not.

See, for example, these articles in Scientific American and Time magazine, which reference this study published in Proceedings of the Royal Society B.

It has (by extension) further been claimed that the birth control pill may inadvertently be responsible for a large share of infidelity, breakups and divorces (see the above links). The reasoning goes as follows: People end up in relationships while the woman is on (or off) the pill. As soon as the woman stops (or starts) taking the pill, her preferences change, which eventually assists in the relationship's demise.

Since I am not very knowledge about biology, I was wondering about two things:

  1. How solid is the science on this? Was this just a single study that was overreported and may as well have been a fluke, or is it safe to assume that this is correct?

  2. Is the reported effect truly strong enough to warrant the conclusions offered (more divorces and breakups), or is this just another correlation vs causation error?

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    Interesting, too, the idea that a similar effect happens during pregnancy. – Dan Getz Mar 24 '16 at 20:57
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    Just a thought regarding (2). When a behaviour is influenced by many factors, a change doesn't have to be big enough to single-handedly change any one individual's behaviour in order to still result in measurable changes across a population. E.g. even if no individual ever thinks "I'd buy that if it was $0.01 cheaper", a $0.01 price increase would measurably reduce sales across a population if reduces the probability of an undecided person thinking "Ummm... okay!" instead of "Ummm... no, maybe later" from 50.0% to 49.9%. Same with "Ummm... We need to talk." vs "Ummm... I'm okay I guess..." – user568458 Mar 24 '16 at 21:22
  • My reading of the study abstract suggests the exact opposite conclusion. Women on the pill were more likely to be consistent in their preference for the odour of MHC-similar men, both in and out of relationships, unlike untreated women who were more likely to change their preference. Did I misunderstand? I guess the risk is that stopping the pill might reduce the mate-preference equivalent to someone who has never been on the pill. – Oddthinking Mar 25 '16 at 7:09
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    "Is the reported effect truly strong enough to warrant the conclusions offered (more divorces and breakups), or is this just another correlation vs causation error?" Firstly, that's a false dichotomy. But looking at the study and the articles, they are careful to tiptoe around how strong the effect might be, or even if the effect exists, so this is unanswerable. – Oddthinking Mar 25 '16 at 8:46
  • @Oddthinking: I suppose a lot of it depends on which is seen as a more likely and lasting change, going off the pill or pregnancy. In both cases, there seems to be a switch during that time period. The former can come as a shock, particularly since the pattern is likely to be on contraception prior to marriage and off after (when looking at kids), which may lead to a "suddenly realizing you're not that attracted to them" situation versus pregnancy where it's culturally more of a "hands off until the baby's born" thing. – Sean Duggan Mar 25 '16 at 11:42
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Alexandra Alvergne, Viri Lummaa [2010]

Abstract:

Here, we review support for such conclusions and speculate on the consequences of pill-induced choice of otherwise less-preferred partners for relationship satisfaction, durability and, ultimately, reproductive outcomes.

Central (supportive) argument in the paper for your claim

Hormonally based contraception inhibits the release of FSH and LH and thus softens the normal mid-cycle peak in oestrogen level and elevates progesterone levels (Figure Ib). These hormonal changes prevent ovulation and mimic the hormonal state of pregnancy, which is predicted to modify human female sexuality. In line with this, women using the pill do not appear to exhibit typical oestrous sexuality, but instead display preferences and interests similar to those of women in the non-fertile phases (Table 1, main text).

Conclusion

There is emerging evidence that the use of the pill by women can disrupt: (i) the variation in mate preferences across their menstrual cycle; (ii) their attractiveness to men; and (iii) their ability to compete with normally cycling women for access to mates. [...]. We thus suggest the need for further studies using within-individual designs, and investigating whether general differences between pill users and non-users account for the effect of the pill on mate preferences. Whether the influence of pill use on mate preferences then interacts with actual mate choice is an open question

No final yes but a 'there is evidence.'

Anthony C. Littlea,Robert P. Burrissa,Marion Petrieb,Benedict C. Jonesc, S. Craig Robertsa [2013]

They performed two studies. One using 55 women which were shown faces and had to rate them.

In our first study we experimentally examined change in preferences following initiation of pill use. We recruited an experimental group and a control group of women who completed two facial masculinity preference tests with an interval of approximately three months.

One in which they analyzed 170 couples on the correlation between the masculinity of the male face and the usage of the pill when starting the relation.

we conducted a second study on an age-matched sample of 85 couples who reported using, and 85 couples who reported not using, the pill at the time of partnership formation. Standardized front-on neutral photographs were taken of the men. We determined men's masculinity in three ways: [...]

Conclusion:

Our first study represents the first experimental demonstration that pill initiation changes visual preferences for a trait associated with mate-quality, complementing within-subject demonstrations that pill use can change odour preferences for genetic similarity (Roberts et al., 2008). Effects were only seen for preferences for opposite-sex faces, suggestive that the effects of pill use influence mate preferences but not general preferences for faces. [...] The second study builds on our experimental demonstration of changed preferences, documenting a downstream consequence of pill use during formation of actual partnerships, suggesting that altered preferences lead to altered mate choice. Original face images and computer generated images of women's partners, whom they met while using the pill, were judged as less masculine than those of women who met their partner when not using the pill.

My conclusion would be that there is strong evidence, and a good explanation, that women do change they preferences depending on whether they are on the pill or not. There is also a lot of related research on women preferences during the menstrual cycle which touches this topic as the pill influences said cycle.

Concerning the causation error you mention in part 2 I was unable to find a paper covering this topic but the first paper does say something on that topic:

Studies that compare divorce rates or marital satisfaction across societies that differ by the prevalence of pill use but are similar in, for example, social tolerance for divorce and use of contraceptives might prove helpful in understanding whether marital dissatisfaction owing to the effect of the pill on mate choice could influence the duration and the stability of long-term relationships.

This indicates that - at least at 2010 - there was no such study to swing the conclusion one way or the other.

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+100

How solid is the science on this? Was this just a single study that was overreported and may as well have been a fluke, or is it safe to assume that this is correct?

Multiple studies suggest that hormonal birth control changes how women perceive their partner's face:

  1. Russell 2014
  2. Scheele 2015
  3. Cobey 2014

However, the study you cited (Roberts 2008) doesn't talk about facial attractiveness, but instead about odor preferences. This is based on the idea that women normally prefer the odor of genetically dissimilar men, but that when on hormonal birth control, they instead prefer the scent of genetically similar men.

There is a very small body of other research to back up those claims. Wedekind 1997 provides support to the idea that hormonal contraceptives change a woman's odor preferences for a mate. These two studies have a decent sample size and do agree with each other, but further replication may be required before we can conclusively say that birth control changes women's scent preferences.

However, considering both the facial studies and the scent studies, it seems that birth control does influence a woman's preferences for a mate.

Is the reported effect truly strong enough to warrant the conclusions offered (more divorces and breakups), or is this just another correlation vs causation error?

The author of the study you cited also conducted research on relationship satisfaction: Roberts 2011 claims that women on birth control are less satisfied by sex with their partner, less attracted to their partner, and more likely to initiate a breakup if a breakup occurred. However, it also claims that women on birth control were less likely overall to breakup with their partner.

Since that study only examined women who were mothers, we can also examine the findings of the large scale study Klapilová 2014, which did not measure relationship satisfaction but did measure sexual activity. It found that women on birth control have more sex with their partners and are not more likely to cheat on their partners.

There is some evidence that birth control makes women more jealous, but also that it makes them try harder to keep their partner.

Overall, there is insufficient scientific evidence to assert that birth control causes more breakups or divorces.

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