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Recently I hear more and more often about the correlation between the digit ratio and the behavior of a person (or even his successes studying scientific subjects, etc.)

Are there any large-scale scientific experiments that examine this claim?

Example claim:

Like science-backed palm reading, new studies use digit ratio to predict aggressive behavior and risk of disease.1

1Finger Length Predicts Health and Behavior

Sklivvz
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  • While there's surely a good question here, this is a lot of completely different claims. Can you clarify what claim you are interested in validating? – Sklivvz Feb 08 '14 at 11:37
  • Thanks :) I want to understand if there really is any kind of correlation between the Digit ratio and the person behavior/way of thinking. I mean, is there a way to deduce information about the person standing in front of me using digit ratio? – Infinity Feb 08 '14 at 12:24
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    Yes, if they're seriously examining your digit ratio they're firm believers in bad pseudoscience. :) – Shadur Feb 08 '14 at 12:52
  • @Infinity While these studies do show significant associations, they are mainly used to establish a link to prenatal testosterone, not to predict personality from digit ratio (only in the statistical sense, job interviewers shouldn't rely on this). The size of the associations is generally small and you would be better off talking to a person or looking at them for a minute to deduce personality. – Ruben Feb 19 '14 at 11:10

2 Answers2

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The Wikipedia page on Digit Ratio provides a good background and references dozens of studies divided up into areas such as physiology and disease, psychological disorders, physical and competitive behaviour, cognition and personality, management, sensory perception and sexual orientation.

Some relevant results to personality to the question:

  • Lesbians are more likely to be femme and less likely to be butch with a high digit ratio.
  • Aggression in males and assertiveness in females is associated with low digit ratio.
  • Paranormal and superstitious beliefs among men with a higher digit ratio.
  • Increased Anxiety in males with a higher digit ratio.
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Finger ratio is an indication of prenatal testosterone in relation to estradiol. In "2nd to 4th digit ratios, fetal testosterone and estradiol" Lutchmayaa et al report:

Results: A significant negative association between right 2D:4D ratio and FT (fetal testosterone) /FE (fetal estradiol) ratio, which was independent of sex. Conclusions: These preliminary findings lend support to an association between low 2D:4D and high levels of FT (fetal testosterone) relative to FE (fetal estradiol), and high 2D:4D with low FT (fetal testosterone) relative to FE (fetal estradiol).

But it's also a predictor of current testosterone as shown in "The ratio of 2nd to 4th digit length: a predictor of sperm numbers and concentrations of testosterone, luteinizing hormone and oestrogen."

The dimorphism is present from at least age 2 years and 2D:4D is probably established in utero; (ii) high 2D:4D ratio in right hands was associated with germ cell failure in men (P = 0.04); (iii) sperm number was negatively related to 2D:4D in the right hand (P = 0.004); (iv) in men testosterone concentrations were negatively related to right hand 2D:4D and in women and men LH (right hand), oestrogen (right and left hands) and prolactin (right hand) concentrations were positively correlated with 2D:4D ratio and (v) 2D:4D ratio in right hands remained positively related to luteinizing hormone and oestrogen after controlling for sex, age, height and weight.

Testorsterone has a lot to do with personality and therefore you can use the finger ratio as an imperfect predictor of personality.

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