Together in my washing machine.

I separate out washing according to colour fastness, temperature tolerance, and the delicacy of fabric. Seeing you're so keen to find out how the rest of the world launders their smalls, MoL, can you tell us exactly why Chinese people wash their socks and underwear separately? Is it a hygiene issue? And what about other garments? Do you wash shirts on their own? If not, do you put shirts in with the socks or the undies? And the the thing that we most want to know is this: why are you asking? What do you hope to learn?

I wash them in the washing machine with all my other clothes. The only clothes I separate are my whites.

How will this question tell you about the cultural difference???