So girls are less interested in these subjects, but in more unequal countries (read poorer) they do it for career prospects, while in more equal countries (read richer) they do what they want (not STEM subjects).
In richer countries the family and friends force/pressure girls to do "girly" things and study a non STEM subject, but in poor countries they can do whatever is necessary for survival and can choose a better paying field, like STEM if they want.
It's a difficult subject, because it's almost impossible to make a controlled experiment and distinguish which explanation is the correct one. (You can't get a million subject and create 10-20 isolated societies with a different level of resources and initial culture and measure the results 100 years later.)
I also would like to see the correlation with the number of "stay at home moms". In some rich countries is common that after marriage / the first child the mom left the work. In poor countries it's more difficult and both parents must have a paying work. Why study a long career if you are not going to work too long in the field?
(Interesting psychological study, why you're being downvoted for saying that. Maybe that people are nowadays conditioned to assume any talk of gender differences is sexism, I've noticed.)
This would heavily imply some level of social conditioning to be the cause for disinterest.
> The researchers, from Leeds Beckett University and the University of Missouri, believe this might be because countries with less gender equality often have little welfare support, making the choice of a relatively high-paid STEM career more attractive.
The downvoters should explain themselves.