Researchers are struggling to understand why girls are more "afraid" of maths than boys.

Female teenagers were found to suffer from anxiety over mathematics more than males in 80% of countries looked at in a new study.

Furthermore, the results were more pronounced in countries with higher gender equality - throwing doubt on the idea that strong female role models are the key to getting more girls to opt for science, technology, engineering and maths (STEM) subjects.

Mathematics anxiety is defined as negative feelings experienced during the preparation of and engagement in maths activities - a psychological factor that can stop people pursuing the subject.

A team of researchers from Glasgow University and the universities of California, Irvine and Missouri in the US analysed student performance in 15-year-olds from the Programme for International Student Assessment (PISA), putting the data up against socio-economic indicators.

In Italy and Mexico, where there is less gender equality, both boys and girls were shown to have a relatively high score on maths anxiety but there was no difference in the level between sexes.

In the more gender equal countries of Norway and Germany, maths anxiety was lower but the difference between boys and girls was larger.

Parents in more developed countries generally were seen to place a stronger emphasis on the mathematical development of their sons than their daughters, despite the fact they have larger proportions of mothers working in the STEM sector.

Dr Gijsbert Stoet, from Glasgow University's School of Education, said: "Social commentators keep mentioning the importance of female role models in STEM.

"If such role models were really so important, we would have expected that countries where more mothers work in the STEM sector would value mathematics for boys and girls equally.

"This is not the case and matches other research that same-sex role models make no difference.

"Policies to attract more girls and women into subjects such as computer science, physics and engineering have largely failed.

"Gender equality is a key humanistic value in enlightened and developed societies but our research shows that policy-makers cannot rely on it as the sole factor in getting more girls into subjects like physics and computer science.

"It is fair to say that nobody knows what will actually get more girls into these subjects - if anyone knows, they have been very good at keeping it a secret."