Does porn exposure create peculiar sexual interests? RCT suggests no

One proposed cause of peculiar sexual interests is porn depicting the interests in question. There’s clearly a correlation between use of such porn and having such interests, but the immediate problem is that this correlation could just as well be due to causation in the reverse direction; there’s no doubt peculiar sexual interests will lead to use of porn depicting such interests.

To test the association, I posted a survey to /r/SampleSize titled “Can you look at some porn For Science? Survey #5”. Among a huge range of other things, the survey contained an opt-in section showing porn depicting a random out of three sexual interests: autogynephilia (a comic depicting the Marvel character Thor transforming into a woman, a captioned picture of a nude woman getting a massage with the captions explaining that she used to be a man, and a picture of a woman having sex shown from her point of view), bondage (three pictures which each depict a man and a woman tied up with rope), and feet (three stock photos showing male and female feet… yeah, I might’ve been a bit lazy in getting pictures for this sexual interest). Furthermore, before and after being shown the porn, participants were asked about their sexual interest in the kinds of things depicted by being asked to rate their arousal to the following:

  • Imagining being the opposite sex
  • Tying up your partner (using rope)
  • Being tied up by your partner
  • Caressing your partner’s feet

The hypothesis I am examining is whether exposure to the corresponding types of porn will cause an increase in the above interests.

As a sample size, in total I got 1052 male participants who opted in to seeing the porn and who completed all of the relevant questions. About one third of these were randomly assigned to each type of porn.

Initial sexual interests

The different sexual interests varied somewhat in their prevalence, as can be seen below:

tested_interests

Frequency of various degrees of endorsement of various sexual interests.

I think these rates are higher than what is typically seen in the general population, but it’s what I usually get on reddit. This seems to be because reddit is unusually paraphilic. In order to perform the analysis, I coded the degrees of interest using integers from 0 to 4. When people rated their arousal to the stimuli, they rated them using integers from 0 to 0 to 6.

Validity of stimuli used

First, it might be a good idea to examine the validity of the stimuli used. Below, I show the univariate regression slopes from a number of sexual interests (listed along the y-axis) to a number of stimuli (listed along the x-axis):

12

Regression slopes indicating how much an expressed sexual interest was associated with arousal to the given stimuli. The last three columns are a breakdown of the stimuli used for autogynephilia, as I perceived them to be more conceptually heterogeneous than the stimuli used for the other sexual interests. As comparisons, I’ve also added two extra sexual interests (“Sex with a man”, “Sex with a woman”), as well as corresponding stimuli (erotic images depicting either men or women).

As can be seen, each stimulus has reasonably high validity; for instance, they all exceeded a slope of 0.4 from the sexual interest they were intended to measure, and the highest slope for each sexual interest was for the stimulus intended to tap into the sexual interest. One problem with validity, though, was that the autogynephilic stimuli were also arousing to heterosexual men. This problem is probably to be expected, as a typical autogynephilic stimulus will depict a woman, which seems like it would be sufficient to be arousing to gynephiles too.

Basic results

When comparing the control group and the intervention group, we didn’t see much effect:

Interest Group Before After
Imagining being the opposite sex Control (n=725) 1.35 (1.36) 0.93 (1.15)
Intervention (n=378) 1.32 (1.38) 0.91 (1.12)
Tying up your partner Control (n=730) 2.04 (1.27) 2.08 (1.3)
Intervention (n=373) 2.01 (1.36) 1.96 (1.32)
Being tied up by your partner Control (n=730) 1.77 (1.35) 1.83 (1.36)
Intervention (n=373) 1.71 (1.39) 1.73 (1.39)
Caressing your partner’s feet Control (n=751) 0.97 (1.09) 0.97 (1.11)
Intervention (n=352) 1.0 (1.12) 0.79 (1.05)

The “Before” column shows the average interest before exposure to the stimuli, while the “After” column shows the average interest after exposure to the stimuli. I’ve written the standard deviation in parentheses after each result.

The main change is that for both the control and intervention group, interest in autogynephilia was reduced in the “after” condition compared to the “before” condition. I believe this is because I asked individuals who reported any interest in autogynephilia in the latter case to give a qualitative description of what autogynephilic things they were into; it seems this lead to some of them no longer reporting AGP interest. This problem makes some forms of data analysis less workable, but it should not be a major problem as it applied to both the control group and the intervention group.

To test whether the intervention had any effect, I computed the change in arousal before and after having the intervention.

Interest Group Change p
Imagining being the opposite sex Control (n=725) -0.41 (0.87)
Intervention (n=378) -0.39 (0.88) 0.719 NS
Tying up your partner Control (n=730) 0.03 (0.67)
Intervention (n=373) -0.05 (0.67) 0.061 NS
Being tied up by your partner Control (n=730) 0.05 (0.64)
Intervention (n=373) 0.04 (0.6) 0.798 NS
Caressing your partner’s feet Control (n=751) -0.01 (0.65)
Intervention (n=352) -0.18 (0.66) <0.001 ***

Out of these, the only significant effect was for “Caressng your partner’s feet”, but it was the opposite direction of what would be predicted by porn causing it. (Perhaps a result of me using poor-quality stock photos for the stimulus? Not sure.)

Heterogeneity

This tells us that on average, porn doesn’t cause peculiar sexual interests. However, possibly one might hypothesize that the effects differ depending on the individuals; maybe porn turns some autogynephiles non-autogynephilic, but also turns some non-autogynephiles autogynephilic.

One possible sign of heterogeneity would be if the intervention group has higher variation than the control group in their degree of change in sexual interest. This does not seem to be the case, though I think I need very large sample sizes to detect it through this means, so it’s not a great method.

Rather, let’s look at it in a different and probably more relevant way: Among those who report being “Not at all” interested to begin with, how interested are they afterwards? This tells us something about whether porn can create an interest in someone who doesn’t have it to begin with.

Interest Group After p
Imagining being the opposite sex Control (n=268) 0.15 (0.48)
Intervention (n=145) 0.1 (0.38) 0.247 NS
Tying up your partner Control (n=88) 0.31 (0.53)
Intervention (n=59) 0.22 (0.52) 0.309 NS
Being tied up by your partner Control (n=153) 0.25 (0.49)
Intervention (n=92) 0.17 (0.43) 0.183 NS
Caressing your partner’s feet Control (n=301) 0.14 (0.38)
Intervention (n=142) 0.1 (0.3) 0.231 NS

There was no evidence that porn exposure could cause sexual interests among those who did not already have them, and in fact all the signs pointed in the opposite direction.

Discussion

At first glance, this might look to be in contradiction with what other studies on boots fetishism (1, 2, 3) found. They found that by pairing an unconditioned stimulus (i.e. a stimulus that the subjects are already attracted to) with a stimulus of a boot, they could make the subjects get erections to boots in isolation. My primary worry with these sorts of studies is that possibly they don’t actually create a sexual interest in boots, but instead set up an expectation that boots will be followed up with an attractive stimulus, which might lead to erections upon seeing boots in anticipation of seeing the attractive stimulus. They did not ask the men whether they were interested in the boots themselves, but instead merely measured their penile arousal to the boots. In addition, they found that repeated exposure to the boots would extinguish the tendency to get erections to them, which seems different from how fetishism usually works (being seemingly stable over longer periods of time).

My survey implicitly included pairings with unconditioned stimuli; the autogynephilic stimuli were somewhat arousing to straight men, and the bondage stimuli were somewhat arousing to men regardless of orientation, presumably because in addition to containing the kinks of interest, they also contained men and women, at least one of which people typically find attractive.

One possibility is that these sorts of effects would only come into play with extended exposure to the porn. But why would someone get extended exposure without being into it in the first place? The main suggestion I’ve heard for this is if one already has ended up with one peculiar sexual interest, then one might end up “picking up” adjacent ones that fit well with the one one has, and thus tend to co-occur in the same erotic material. But this is a pretty speculative theory that lacks evidence.

There are some anecdotal observations of people getting new kinks when encountering a new form of porn. This result throws doubt on them, but it also throws doubt on the common alternate explanation, that people “discover” their kinks from such porn; if a discovery effect applied, then it seems like that should also be found by my survey. However, as my survey was 18+, it does allow early-life discoveries, as well as early-life modifications of one’s sexuality. Such effects are speculative, though. It also does allow the possibility that people’s sexual interests regularly change and people somehow rapidly discover the porn that matches their new interests, faster than I would be able to “catch” in my survey.

The subset of the data collected for the survey that is relevant to this analysis is available here. Note that some people opted not to have their results shared publically, so this dataset will not be quite the same as the one I performed this analysis on.

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