A person's name is Alex. With no other information, you assume that they are . . .
My assumption would be male. I'm aware that it can also be a female name, but I've never encountered one in real life (just in a mystery series). I'm also aware that assumptions can be wrong, so I don't view them as immutable.
Alex is one of the few names I view as unisex so I would probably just think of them as sexless until I got more information.
Seriously, 100% male? Alex is supposed to be a fairly unisex name . . . let's try again.
I probably don't make an assumption until I get more info
My daughters name is Sam. My mother in laws name is Billie. Our female cat's name is Charlie.
We also have a female cat named Charlie!
This weird, but since you are a guy asking the question, I immediately thought male.
If a female asked it, I'd think female.
Interesting. I thought that it might depend on the person answering's gender, not the gender of the asker.