Thursday, 18 September 2014

Fingers, feminism, and bossiness


In the early history of science fiction, and indeed fiction as a whole since Mary Shelley’s Frankenstein, there has been a fascination with humans who have been taken over by sinister forces. In one very early TV science fiction program the small American town was taken over by aliens (yet again: why don’t aliens take over towns in other countries?) who did their dastardly alien tricks on upstanding citizens, operating on them and then releasing them to carry out alien orders.

How to distinguish these interstellar traitors from fine, upstanding, 100% Americans? Even as a child I could see the answer: there were clear drill marks on the back of the necks of the zombies, where something had been implanted: Communism, most probably. However, in this drama, possibly because the drill marks were generally obscured by clothing, another test was applied by the besieged townfolk: the aliens implanted into the bodies of Americans were unable to properly flex their little fingers. Ask them to flex their pinky finger, and democracy is saved.

I have not been particularly interested in fingers. I concede that they are useful, and that to be without them would be a human tragedy, but even in my gratitude I have not accorded them high status.

Now young Woodley strides onto the scene, to remind me that much of great import may be derived from the study of finger length ratios.  Looking at your hands, palm downwards, you will note that when you compare your index finger (number 2, where your thumb is number 1) with your ring finger (number 4) you will find that….. that finger 4 is visibly longer than finger 2. Or perhaps not. The ratio of finger lengths may be a sensitive measure of pre-natal androgen, or a random variation which should not concern us very much, unless we are intrinsically interested in fingers.

Madison, Aasa, Wallert, and Woodley (2014) Feminist activist women are masculinized in terms of digit-ratio and social dominance: a possible explanation for the feminist paradox.

We measured the 2D:4D digit ratios (collected from both hands) and a personality trait known as dominance (measured with the Directiveness scale) in a sample of women attending a feminist conference. The sample exhibited significantly more masculine 2D:4D and higher dominance ratings than comparison samples representative of women in general, and these variables were furthermore positively correlated for both hands. The feminist paradox might thus to some extent be explained by biological differences between women in general and the activist women who formulate the feminist agenda.

They got 25 women at a feminist conference to have both hands scanned (so that finger length ratios could be calculated) and then 24 of them filled in a “Directiveness” questionnaire, which seems to measure dominance and a tendency towards bossiness.

In summary, the feminist activist sample had a significantly smaller (i.e., masculinized) 2D:4D ratio than the general female samples. The size of this difference corresponds approximately to a 30% difference in prenatal testosterone/estradiol ratio, which was the index found to have the strongest association with 2D:4D (Lutchmaya et al., 2004). Directiveness self-ratings also exhibit a large and highly significant difference in the predicted direction. It is notable that the feminist activist sample 2D:4D was also more masculinized than those of the male comparison samples, except for the left hand in the aggregate sample (see Table 2).

This is a small sample, though a big number of feminist activists, given their rarity in the population, and the association with dominance is intriguing.

So what, and what does this have to do with intelligence? Nothing directly. However, there have been claims that the 2d:4d ratio is weakly correlated with intelligence (in another small sample of people).

Marc F. Luxen and Bram P. Buunk.  Second-to-fourth digit ratio related to Verbal and Numerical Intelligence and the Big Five. Personality and Individual Differences 39 (2005) 959–966

There may be something in this finger business. It would be worth checking on a much larger representative sample which has already been tested for intelligence or scholastic ability, and ideally on which genomic data is available.


  1. Woodley is ballsy, I'll give him that.

    1. speaking of ballsy, perhaps we should look into the distance between um, well, that is which side hangs lower - how they're differentially hanging, so to speak - if there is anything to finger ratio, then perhaps ball ratio (scrotal differential?) should be investigated as a possible predictor of... well at least something... by chance, anyway :) cheers!

  2. The 2D4D stuff is fascinating but I'm leery, and predict this topic will die a slow research death over the next 10 or so years.

    How to interpret data when each hand has a different ratio (within persons), and the results (for groups) are only significant for one hand, as in both studies you reference?

    How do hormones differentially affect the right versus left hand ratios?

  3. I am not worried by left hand right hand differences, and all symmetry measures can be looked at, including the lower hanging testicle, but I think the starting point is to see if anything can be replicated on larger representative samples.

  4. I respectfully disagree with Bryan - I think there's definitely something in the 2D:4D ratio and that it's going to attract continued interest in the coming decades.

    Whilst I'm not aware of any studies on large representative samples that have looked at intelligence and the 2D:4D ratio, there have been a few studies looking at other characteristics and the 2D:4D ratio that have been completed on very large sample sizes and shown statistically significant relationships.

    The BBC did a massive survey a few years ago looking at sex differences in the brain and as part of that asked participants to measure their 2D:4D ratio as well as answer a host of other questions. There were over 250,000 participants who submitted their 2D:4D ratio. John Manning, the scientist who first came up with the digit ratio theory, then analysed the data. He verified that (a) men tend to have lower 2D:4D ratios than women, (b) straight men tend to have lower 2D:4D ratios than gay men, (c) black men tend to have lower 2D:4D ratios than white men, (d) men with lower 2D:4D ratios then to have better spatial ability than men with higher 2D:4D ratios. Pretty amazing!

    More recently some developmental biologists at the University of Florida came across the 2D:4D ratio and decided to test the theory on mice embryos. They confirmed that manipulating the hormones that the mice were exposed to in the womb affected the length of their fingers as predicted:

    There have been a few TV documentaries that have looked at the 2D:4D ratio. John Manning appeared on the BBC documentary Secrets of the Sexes to discuss his theories and agreed to predict the placings in a 5000m race based solely on the participants’ finger lengths. The results are pretty impressive:

  5. Michael A. Woodley27 September 2014 at 13:56

    John Manning was not the originator of the finger-ratio-as-psychometric-corollary paradigm - that was Glenn D. Wilson. Sex differences in digit length were noted as long ago as the 19th century (Ecker, 1875). The first paper investigating the association between 2D:4D and personality was published by Wilson in 1983 and employed a sample of 1,000 women recruited with the help of the UK Daily Express newspaper. In that study he found positive correlations between self-ratings of "assertive and competitive" temperament and masculinized 2D:4D ratios. We replicated this in our own smaller sample using John Ray's Directiveness scale.


    Ecker, A. (1875). Einige Bemerkungen über einen Schwankenden Charakter in den Hand des Menschen. Archiv fur Anthropologie, 8, 68–74.

    Wilson, G. D. (1983). Finger length as an index of assertiveness in women. Personality & Individual Differences, 4, 111–112.

  6. @Panjoomby

    I believe ano-genital distance is also beleived to be correlated with testtoserone levels at different stages throughout development. Same with hip/girdle shape.

    @ Michael A. Woodley

    Has there been any further research along the lines of this article as I find it particularly interesting?