Red is sexy but not sexual

The Methods section of most papers is the least read part of the paper. You can see this in how some journals print the Methods in a tiny point size. Others have taken to putting the section at the end of the paper, so as not to disrupt the narrative flow with details.

Occasionally, you get a paper – usually in your field – where you need to read the Methods section closely to understand a paper enough to criticize or replicate.

Rare indeed are papers where the story is so unusual that I think, “I have absolutely got to read that Methods section!”

A new paper by Johns and colleague marks the first time I thought, “I have to read those Methods,” and “These Methods should come with an NSFW warning.”

It’s about the colour red.

Red seems to affect us in a way that other colours don’t (Elliot et al. 2007, Hill & Barton 2005). Case in point:

These head-turning dresses would not be the show-stoppers they are if they were beige.

Red is sexy.

If that picture doesn’t convincing you, check out Elliot and Niesta, 2008 and go through the data to your heart’s content.

Johns and colleagues test an hypothesis for why red on women looks so attractive to me. The hypothesis is that red is sexy because it reminds men of... lady parts.

An obvious objection to this idea is that t external sex organs of women are not red in the way that the dresses above are red. The hypothesis is a more subtle, however. One version of the hypothesis is that as females are approaching ovulation, the vulva becomes more red than is is at other points in the cycle.

If this “red is code for female sex organs” hypothesis is true, you might predict that men would judge female genitals as more attractive as they became more red.

The Methods section does not disappoint.

Explicit images of anatomically normal, un-retouched, nonpornographic, similarly-orientated female genitals were surprisingly difficult to obtain... We selected photographs that ... did not contain other, potentially distracting, objects (fingers, sex toys, piercings etc.) and were hairless to account for current fashion.

Ah, scientific prose, you’re at your most amusing when you’re trying to act coy.

They showed their pictures to 40 males. Most of the men were in their 20s, and they asked the participants about factors like their sexual orientation (they all reported themselves to be straight) and number of sexual partners. The men rated the attractiveness of each image.

The ratings of attractiveness were the exact opposite of those predicted by the signalling hypothesis. The reddest images were rated the least attractive.

The authors are then tasked to come up with an hypothesis as to why redness is less attractive. Their suggestion is that red is suggestive of menstrual blood. I'm not sure how one would test this hypothesis.

The results also showed that there was no difference in the judgments of men depending on their sexual experience. I learned from the Methods section of this paper that... shhhh, don’t spread this around... one can find pictures of female genitalia on the Internet. Is is possible that the men in this study knew this and might have looked at pictures of ladybits before participating in the study? I know, it’s incredibly unlikely, am I right? But if they did, it might explain why they found no difference in attractiveness ratings according to number of partners the men had.

This study is useful in that it tries to test an adaptive hypothesis experimentally. But it is frustrating because it is a limited study and hard to interpret.

First, there were few stimuli used. Only four pictures were used (then coloured four shades of red, for a total of 16).

Second, and more importantly, for an hypothesis that is all about sex, the authors seemed determined to make everything as clinical and detached and, well, unsexy as possible. First, the pictures were substantially cropped. They didn’t show the labia minora or the clitoris. (Correction; see comments.) As mentioned in the quote above, they didn’t want to use images had any sort of sexual nature (non-pornographic). The female equivalent of this task might have been to evaluate penises for attractiveness from pictures that only showed a flaccid member.

Perhaps not surprisingly, the men didn’t find images of lady parts alone to be very attractive. On a scale of 1 to 100, the average was around 40, except for the reddest, which was rated 35.

I’m curious as to whether the authors would expect to see the same effect with homosexual women.

Finally, there is a great opportunity for further research. The authors note:

Surprisingly little is known about the range of variation in morphology and colour of the external genitalia of normal women of reproductive age, however, and further research is necessary in this area.

I think this could be the chance for someone (not me) to create the best citizen science project ever. “Ladies, all you need to contribute to science is privacy and a camera.” We need data!

Additional: Another take at The View from Helicon.

Reference

Changizi MA, Zhang Q, Shimojo S. 2006. Bare skin, blood and the evolution of primate colour vision. Biology Letters 2(2): 217-221. http://dx.doi.org/10.1098/rsbl.2006.0440

Elliot AJ, Maier MA, Moller AC, Friedman R, Meinhardt J. 2007. Color and psychological functioning: The effect of red on performance attainment. Journal of Experimental Psychology: General 136(1): 154-168.

Elliot AJ, Niesta D. 2008. Romantic red: Red enhances men’s attraction to women. Journal of Personality and Social Psychology 95(5): 1150-1164.

Hill RA, Barton RA. 2005. Psychology: Red enhances human performance in contests. Nature 435(7040): 293-293. http://dx.doi.org/10.1038/435293a

Johns SE, Hargrave LA, Newton-Fisher NE. 2012. Red is not a proxy signal for female genitalia in humans. PLoS ONE 7(4): e34669. 10.1371/journal.pone.0034669

This article is made possible thanks to Helen Lewis, who compiled covers of book on female sexuality for New Statesman.