[Update: Since I wrote this post, Weeden re-did some of his results – including his abortion results – controlling for ideology.  I leave judgment to the reader.]

[Further Update: I didn’t notice that the abortion opinion measure I was using coded “not asked” as “no.”  Corrected regressions here.]

In The Hidden Agenda of the Political Mind, Weeden and Kurzban argue that individuals’ “inclusive interests” have a large effect on their position on abortion.  On the one hand, this seems implausible.  On the other hand, Jason Weeden wrote his dissertation on abortion attitudes, so there must be something to his story.  What’s really going on?  Like Weeden and Kurzban, I turn to the General Social Study to find out.  My evidence is only exploratory; I don’t pursue every statistical permutation.  However, I did precommit to blog the topic before I looked at the data.

Recall Weeden and Kurzban’s novel claim:

People who party and sleep around have an interest in other people not
bringing legal or moral costs to bear on them for doing so.  People who
want to delay having children while partying and sleeping around have an
interest in the availability of family planning, including the backstop
of legal abortion.  Their mental Boards of Directors will prefer moral
and political policies that help them live the lives they want to live.

The GSS has many measures of abortion opinion, but the best is probably ABORTION, which =1 if the respondent thinks abortion should be legal for any reason, and =2 otherwise.  Given the starkness of the former position, it’s not too surprising that the split is 23/77.

The GSS also has many measures of sexual activity.*  Taking both relevance and missing data into account, the best measures are probably:

1. Number of sexual partners in the last year (PARTNERS), binned into 8 categories:  0=no partners, 1=1 partner, 2=2 partners, 3=3
partners, 4=4 partners, 5=5-10 partners, 6=11-20 partners, 7=21-100
partners, 8=100+ partners.

2. Number of sexual partners in the last five years (PARTNRS5), binned into the same 8 categories as PARTNERS.

3. Lifetime number of male sexual partners (NUMMEN) and female sexual partners (NUMWOMEN).  These measures are continuous, but I recode responses into the same 8 bins as the two previous variables.  The recoded variables are NUMMENBIN and NUMWOMENBIN.

So what happens if we regression ABORTION on a constant, all four measures of sexual activity, age, age squared, year, and SEX (=1 if male, =2 if female)?


Weeden and Kurzban are seemingly on to something.  Every step up the ladder of lifetime partners makes respondents about 2 percentage-points more pro-choice.  Strangely, though, number of partners in the past year and past five years make very little difference; their coefficients are statistically insignificant even though there are over 15,000 valid observations.  In terms of self-interest, of course, you’d expect recent sexual behavior to matter more.

But what happens if we control self-reported ideology, which runs from 1 (most liberal) to 7 (most conservative)?  This.


Left-right ideology is far more important than number of sexual partners.  A single step on the 1-7 ideology ladder matters more than three steps on the lifetime sexual partners ladder.  A liberal virgin is more pro-choice than a conservative with over 100 lifetime partners.

What about religion?  Weeden and Kurzban want to count church attendance as a measure of interests.  The GSS variable is ATTEND, which ranges from 0 (never attends religious services) to 8 (attends more than once per week).  But once you’re controlling for all four measures of sexual partners, it’s hard to see why attendance continues to be a credible measure of sexual risk-taking.  In any case, Weeden and Kurzban neglect a more philosophical GSS measure of religiosity: your views on the Bible.  Response options:

1. The Bible is the actual word of God and is to be taken literally, word for word.

2. The Bible is the
inspired word of God but not everything in it should be taken literally, word for word.

3. The Bible is an ancient book of
fables, legends, history, and moral precepts recorded by men.

What happens if we add ATTEND and BIBLE to the list of explanatory variables?


Left-right ideology remains the strongest predictor, but both religious measures are comparably important.  The coefficients on sexual activity are miniscule by comparison.  Moving from a moderate Christian to a fundamentalist Christian view of the Bible has a bigger effect than moving from 0 to 100+ lifetime sexual partners.

Since Weeden wrote his dissertation on this topic, he surely knows this data better than I do.  Still, I’ll be very surprised if he can add anything to my final regression that makes interests look more important than ideas.  If he posts any such regressions, you’ll be the first to know.

P.S. As far as I can tell, GenCon attendees are liberal and irreligious yet have few sexual partners.  Does anyone who’s attended seriously expect these gamer nerds to be pro-life?

* Weeden and Kurzban have a bunch of other measures of the
“Freewheeling” lifestyle, but it’s hard to see how they remain relevant to the interest-abortion
nexus after controlling for number of sexual partners.  For example, one of
their explanatory variables is how often respondents visit bars.  But
after controlling for number of sexual partners, it’s hard to see how
abortion serves the interests of barflies.