Male scientists are good at research because they have the same hormone levels as women, according to new study involving the measurement of relative finger lengths.

Research into male scientists at Bath University has revealed that they have as much of the female hormone oestrogen as the male hormone testosterone, a combination more usual in women.

This, say the researchers, is why they are so clever.

Previous research has revealed that this unusual combination of hormones leads to better development of the right side of the brain which is where spatial and analytical skills are governed.

The study, which has been submitted to the British Journal of Psychology, also found that women social scientists tended to have higher levels of testosterone, making their brains closer to those of males in general.

The study drew on work over the last few years which established that the levels of oestrogen and testosterone a person has can be seen in the relative length of their index (second) and ring (fourth) fingers. The ratio of the lengths is set before birth and remains the same throughout life.

The length of fingers is genetically linked to the sex hormones, and a person with an index finger shorter than the ring finger will have had more testosterone while in the womb, and a person with an index finger longer than the ring finger will have had more oestrogen. The difference in the lengths can be small - as little as two or three per cent - but important.

A survey of the finger lengths of over 100 male and female academics at the University by senior psychology lecturer Dr Mark Brosnan has found that those men teaching hard science like mathematics and physics tend to have index fingers as long as their ring fingers, a marker for unusually high oestrogen levels for males.

It also found the reverse: those male academics with longer ring fingers than index fingers - the usual male pattern - tended not to be in science but in social science subjects such as psychology and education.

Dr Brosnan said: "This right brain development is at the expense of language abilities and people skills that men with a more usual level of testosterone develop and which can help them in social science subjects like psychology or education."