Our results show that women’s contributions tend to be accepted more often than men’s [when their gender is hidden]. However, when a woman’s gender is identifiable, they are rejected more often. Our results suggest that although women on GitHub may be more competent overall, bias against them exists nonetheless.
How does a photograph disclose someone’s gender?
The study differentiates between male and female only and purely based on physical features such as eye brows, mustache etc.
I agree you can’t see one’s gender but I would say for the study this can be ignored. If you want to measure a bias (‘women code better/worse than men’), it only matters what people believe to see. So if a person looks rather male than female for a majority of GitHub users, it can be counted as male in the statistics. Even if they have the opposite sex, are non-binary or indentify as something else, it shouldn’t impact one’s bias.
Through gender stereotypes. The observer’s perception is all that counts in this case anyways.