Women with long index fingers on their left hands are more likely to have affairs, a study has shown.
The findings have surprised scientists as having a longer index finger is associated with having more typical female characteristics.
The longer index finger and shorter ring finger have been linked to being exposed to higher levels of female sex hormones in the womb.
It was assumed that women who were ‘more feminised’ would be more likely to be satisfied with their romantic relationships, and to be less impulsive.
Being more exposed to the sex hormone oestrogen in the womb leads to women’s index fingers growing longer than their ring finger.
By contrast, being exposed to more of the male sex hormone testosterone in the womb has a more ‘masculinising’ effect – and results in a longer ring finger and a shorter index finger.
Men with longer ring fingers than index fingers have been found to be better sportsmen.
Eiluned Pearce of Oxford University carried out the research which has been published in a Royal Society Journal.
She took measurements of the finger lengths of 274 female volunteers and also sampled their DNA.
They also completed psychological tests on their relationship quality.
She found that ‘women with higher (more feminine) left hand digit ratios are more impulsive and rate their romantic relationships less favourably.’ She added that the finding is ‘intriguing, because the opposite might be expected’.
In the research paper, she speculates that women with the higher index finger to ring finger ration are likely to be ‘more feminized’ and more highly sought after by males.
Because they know they have a lot of options, ‘this might be associated with dissatisfaction with current partners’ and this might lead to flings – or as the scientists call it ‘opportunistic mating’ and ‘impulsive’ mating with men who are not their husband or partner.
The two main strategies in sex are ‘opportunistic mating’ – in other words having lots of flings – and a strategy ‘focusing on long-term commitment’.
She writes that ‘If females with more feminised morphology [body shape] have higher ‘mate value’, this might be associated with dissatisfaction with current partners, leading to impulsive extra-pair matings and seeking alternative mates.’
The researchers also looked at the ratio of index finger to ring finger lengths in males, but did not find any connection with relationship quality.
Last month research found that women whose ring fingers are longer than their index digits more likely to be lesbian.
Researchers at Essex University looked at sets of identical twins where one of the siblings was heterosexual.
They found that the homosexual twin tended to have a greater difference between the length of their index and ring finger, with the difference most pronounced among women.
Previous research has indicated that exposure to the male hormone testosterone in the womb could be linked to differences in finger length and also to sexuality.
Women’s index and ring fingers are typically of similar length while in men there is a greater difference.
Both men and women are exposed to the ‘male’ hormone testosterone in the womb.
The study observed that in 18 sets of female twins, the lesbian twin had more ‘male-typical’ hands than her straight sister.
In 14 sets of male twins the gay twin had slightly more ‘male-typical’ hands than their straight brother but the difference between the two was not viewed as significant.
A chart indicated that the index finger of non-straight women was typically around 90 to 100 per cent as long as the ring finger.