Martijn van Mensvoort - © Hand Research

JUNE 25, 2009

Is 2D:4D finger research misleading / deceptive?

This week Dutch & German popular scientific magazines 'scooped' that Czech researchers found that the 2D:4D finger ratio research is producing misleading results. But actually, the titles chosen by the 'scoop' reviewers are more misleading!

On the contrary, the Czech findings do not contradict earlier 2D:4D findings and likely in time the new findings will be recognized as a new milestone in the 'global' finger research.

The Dutch 'Noorderlicht' reports: 'Vingerverhouding is misleidend'
The German '' reports: 'Trügerische Finger'

The Czech publication
Conclusion: a new milestone in the 'global' finger research!

Take 5: five things that your 5 fingers can tell you.

Research: the index finger versus the middle finger.

The conclusion of this article will describe for you how to value & understand the new findings described by the Czech researchers. But in the continuation of this article you will first find an English translation of the Dutch & German 'scoops' + the abstract report presented by the Czech researchers:


'Vingerverhouding is misleidend' [Fingerratio is misleading]

Noorderlicht reports: fingerratio is misleading?

If someone's index finger or ring finger is longer, depends on the size of the hand.

Do not put too much value to the relationship between the two, say Czech researchers (...!?)

To measurement of the length ratio between index finger and ring finger has become popular since 1998 when John Thomas Manning and colleagues published an article in journal 'Human Reproduction'. They had discovered a link between finger ratio and the number of sperm that men produce. The suspected cause: the more testosterone in the womb (by the fruit or the mother), the shorter the index finger was later compared with the ring finger. At the same time, testosterone affects the formation of the genitals.

Since then, more than three hundred articles published, which includes links to personality, sexual orientation, and general health were established. It is all attributed. Also Lukas Kratochvil and Jaroslav Flegr published this. But now she has doubts about this type of research.

What nobody has all the time, write them now is that the relationship between finger length naturally changes with the size of the hand itself. The bigger the hand, the shorter the index finger relative to. This is true for both men and women. If you do not take into account, writing in Biology Letters, you will get misleading interpretation of your measurements. It would be better for them finger lengths between groups of people to compare, not the relationship between the point and ring finger.

Author: Elmar Veerman


'Trügerische Finger' [Deceptive finger]

Scienceticker reports: deceptive finger?

The fingers are used as indicator of physical and mental characteristics of a human being overestimated. This conclusion establishes a study by two Czech researchers close. The ratio of the lengths of finger and ring finger have therefore varies with the size of an individual. To draw conclusions about talents, the disease susceptibility or even sexual preference taugt therefore limited.

For example, the index finger in males usually slightly shorter than the ring finger, while the ratio for women to balance or even reverse. This difference reflects not only hormonal factors explain Lukáš Kratochvíl and Jaroslav Flegr of the Charles University in Prague in the journal "Biology Letters". A large proportion of the variation already explained by the fact that men are usually bigger and have larger hands than women.

This allometrie-effect may lead to an over-interpretation result, the researchers found in a re-analysis of data from several hundred participants of previous studies. Within an age group increases the length of the finger thus linearly with the ring finger. Purely mathematical starts finger, however, by a margin so that the aspect ratio automatically by an absolute finger length shrinks.

In recent years there has been a veritable boom in studies on finger length ratio. This was triggered by a publication in 1998, the British researchers on a correlation between the length ratio of pointing and ring finger and the sperm count as well as the hormonal balance reported. Since then, more than 300 studies on the subject have been published, inter alia, by itself Flegr

"We do not claim that the previous results for the finger length ratio are wrong," emphasize Kratochvíl & Flegr (...!?)

The relevant conclusions should, however, with the help of methods, including the absolute finger length taken, be reviewed.

At least since the 30 years we know the pitfalls in comparing the proportions of life forms, write the researchers. "Therefore, it is surprising that biological evolution and medical studies, often with conditions such as body mass index or the ratio of waist and hip work."

Author: Meinke


'Differences in the 2nd to 4th digit length ratio in humans reflect shifts along the common allometric line'

The Czech finger research


Ratios often lead to biased conclusions concerning the actual relationships between examined traits and comparisons of the relative size of traits among groups. Therefore, the use of ratios has been abandoned in most comparative studies. However, ratios such as body mass index and waist-to-hip ratio are widely used in evolutionary biology and medicine.

One such, the ratio of the 2nd to the 4th finger (2D : 4D), has been the subject of much recent interest in both humans and animals. Most studies agree that 2D : 4D is sexually dimorphic. In men, the 2nd digit tends to be shorter than the 4th, while in women the 2nd digit tends to be of the same size or slightly longer than the 4th. Nevertheless, here we demonstrate that the sexes do not greatly differ in the scaling between the 2nd and 4th digit. Sexual differences in 2D : 4D are mainly caused by the shift along the common allometric line with non-zero intercept, which means 2D : 4D necessarily decreases with increasing finger length, and the fact that men have longer fingers than women.

We conclude that previously published results on the 2D : 4D ratio are biased by its covariation with finger length. We strongly recommend regression-based approaches for comparisons of hand shape among different groups.

Authors: Lukáš Kratochvíl & Jaroslav Flegr


A new milestone in the 'global' finger research!

The Czech researchers may have found a relationship between increasing finger length (possibly based on the middle finger?) and the decreasing 2D:4D finger ratio (index finger versus ring finger).

The German article includes a very explicitely quote from the authors: "We do not claim that the previous results for the finger length ratio are wrong"...!

But the Dutch article includes some 'suggestive' words: "Do not put too much value to the relationship between the two, say Czech researchers" - but obviously these words are in contradiction with the quote from the researchers themselves - as presented in the German article.

By the way... are the Czech research findings really surprising?

John T. Manning described in his first book 'Digit Ratio' that:
  • 2D:4D finger length does NOT correlate with hand length nor hand width (
    Peters et al. (2000) - see: page 9);
  • 2D:4D finger length does correlate with palm shape: low 2D:4D values correlate with a short, broad hand - indicated by a high AtD-angle in the palmar dermatoglyphics (Manning et al. (manuscript) - see page 9+10);
  • 2D:4D finger length does NOT correlate with the ratio between the index and ring metacarpal lengths in males, nor in females (Wood-Jones (1941) & Phelps (1952) - page 9);
  • 2D:4D finger length does correlate negatively with length of the forearm - when corrected for body height (Tanner (1990) & Manning (manuscript) - page 9);
  • 2D:4D finger length does NOT correlate with body height (see: page 7);

    And Manning described sexe differences in fingers beyond the 2th and 4th digit:

  • 2D:3D finger length ratios (index finger vs. middle finger) are lower in men than in women. Manning's conclusion was: 'This may that the growth of the 3rd and 4th digits are under control of the same factors'. (Phelps 1952 - see: page 12);

    So, the conclusion of the Czech researchers that 'the 2D : 4D ratio are biased by its covariation with finger length', is actually not a big surprize - since it doesn't contradict earlier 2D:4D findings. Likely the new findings will in time be recognized as a new milestone in the 'global' finger research.



    Related sources:
    A new means of measuring Digit Ratio (2008 research)
    Palmistry's digital analogue: is 2D:4D finger length measurement the new chiromancy?
    John Manning presents: 'The Finger Book'
    Body height, finger length & male vs. female differences
    What our fingers can tell us
    Finger length & sexuality: the science of Gaydar
    Five things your 5 fingers can tell you: evolution, sports, social behavior, disease and sex
    Is 2D:4D finger ratio research misleading?
    Double Digits!



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