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1 October 2014
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Sex ID


It's thought that testosterone plays an important role in the way we think and behave. Many of the questions in the Sex ID experiment were related to theories about testosterone.

Man lifting weights
Testosterone helps us build muscle.

The Sex ID test was originally an online experiment. We've stopped collecting data now and many of the questions have been removed from the test, but we've kept the fun stuff!

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The role of testosterone

Testosterone is a male sex hormone required for sperm production, the development of male reproductive organs and the emergence of secondary male sexual characteristics such as facial hair, a deeper voice and muscles.

In men testosterone is produced in the testes and adrenal glands.

Testosterone is also produced in women's ovaries and adrenal glands. Little is known about the exact role of testosterone in women, but scientists believe it helps maintain muscle and bone strength and contributes to sex drive or libido.

On average, men produce between 4 and 10mg of the hormone per day and overall they have about 20 times more testosterone than women.

Testosterone and digit ratio

In the Sex ID test we asked people about their index and ring finger measurements. Some scientists believe that the ratio of index finger length to ring finger length indicates how much testosterone we were exposed to in our mother's womb.

A man and a woman
A BBC One television series Secrets of the Sexes explores brain sex differences.

Higher testosterone exposure is thought to lead to a longer ring finger. This is determined as early as 14 weeks into a pregnancy.

On average, women's index and ring fingers are almost equal in length because they are exposed to less testosterone. In men, the ring finger tends to be longer because they have higher testosterone levels. In general, women exposed to more testosterone have more 'masculine hands' – ie longer ring fingers.

Testosterone and birth order

When the Sex ID test was an online psychology experiment, we asked people about their siblings in order to investigate the theory that pre-natal testosterone exposure changes systematically every time a woman gives birth to a male child. The scientists who designed the survey will compare the number of older brothers a test taker has with their finger measurements to see if there is any correlation.

Testosterone and assertiveness

In the Sex ID ultimatum task people were asked to decide how they would split £50 between themselves and a stranger. Scientists want to find out if there is a relationship between testosterone levels and assertiveness.

It is assumed that people with higher testosterone levels would drive a harder bargain and be less compromising. Research into the effects of testosterone and competitive behaviour suggests that testosterone increases competitiveness and risk taking.

Interestingly, some studies show that testosterone levels in women change according to the status of their occupations.

Back to your results

Take the Sex ID test

Find out about the BBC One television series Secrets of the Sexes

Read about the Sex ID experiment

Sex ID frequently asked questions

Other Sex ID articles:

Brain sex
Spatial tests
Facial attractiveness
Empathising and systemising

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