Martijn van Mensvoort -  Hand Research

October 30, 2007

Double Digits
The digit ratio work of Professor John T. Manning

Marc Abrahams

Aside from jewellers, who are today's finger measurement celebrities? Let's take a look. They - and many other researchers - are building professional reputations by measuring people's fingers.

These digerati specialise in comparing the length of a person's second finger with the length of the fourth finger. In technical lingo, this comparison of digit lengths is called "the 2D:4D ratio". But those in the know often just say "2D:4D".

Professor John Thomas Manning of the University of Central Lancashire (and before that, the University of Liverpool) is the Finger Patriarch. Though by no means elderly, Manning is the Grand Old Man of finger-length ratio science. Many credit him with an idea that goes like this: finger lengths reflect, in some as-yet-to-be-specified way, one's experience in the womb. In particular, the chemicals testosterone and oestrogen play some role in finger-length ratio development. Testosterone and oestrogen also play roles in many other things that happen as a foetus becomes a child and then grows up to be an adult. And so, goes the reasoning, finger-length ratio is related to all sorts of things, somehow.

An overview of Prof. Mannings work on digit ratio:

In a 1998 study, Manning revealed that the ratio of second to fourth digit length is "a predictor of sperm numbers" in men.

In 2000, Manning published a study called The Ratio of second to fourth Digit Length and Male Homosexuality. There he revealed the existence of "a significant positive relationship" between 2D:4D and "exclusive homosexuality".

That same year, in a different study, Manning told of discovering great variations in "reproductive success and 2D:4D from England, Germany, Spain, Hungary (ethnic Hungarians and Gypsy subjects), Poland, and Jamaica (women only)". One minor finding, he said, was that "the English sample also showed that married women had higher 2D:4D ratios than unmarried women".

Topping out the year, he also predicted that "2D:4D ratio is predictive" of the following conditions: infertility, autism, dyslexia, migraine, stammering, immune dysfunction, myocardial infarction and breast cancer.

In a 2001 study, Manning explained that "men and women with low 2D:4D are susceptible to HIV infection and Aids". Also in 2001, he reported that professional football players had lower 2D:4D ratios than other men, and that "football players in first-team squads had lower 2D:4D than reserves or youth team players".

In 2002, Manning published studies explaining that 2D:4D has a relationship to musical genius, and also to skiing performance. He deduced the latter by analysing the ski-run times and finger lengths of 72 skiers, each of whom skied twice over a 200-metre slalom course. His discovery: that "low 2D:4D was associated with fast skiing times".

In 2003, Manning reported, in separate studies, that in men, 2D:4D is "related to perceived dominance and masculinity but not attractiveness", and that 2D:4D might be useful for predicting which preschool children will grow up to be psychopaths.

Next week we will peek at some of the other brightly blazing academic finger stars.

Marc Abrahams is editor of the monthly Annals of Improbable Research
and organiser of the Ig Nobel Prize


Related sources:
Double Digits at The Guardian
Talk to the Hand
Giving science the Finger
Finger Length (2D:4D) moderates the impact of an aggressive music video on aggression
Length of Fingers show how 7-year-old children will do at maths or English
Pointing a Finger at sports success




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