The paper cited by Mr Magnetic, apparently written in 2015 (no explicit date in the PDF that I can see) writes in terms of binary difference between male pilots and female pilots. But in today's world the person in the other seat may be M or F or anywhere in the LGBTQ spectrum – and Ms and Fs are spectrums in themselves, too, varying a lot in personality and ability to communicate. What matters is that the captain and FO can work together professionally, whatever their gender or other characteristics. If they can't or won't, they're an accident waiting to happen, as many actual accidents have shown. Never forget that it was an M sky-god captain who initiated take-off in fog so thick that he couldn't see, until it was too late, the lights of a 747 backtracking towards him (which he knew was out there but didn't make certain of its position), ignoring his M junior co-pilot's attempt to warn him that that 747 was not clear.