They don't know how they do it because they delegate it to specialized hardware. You have specialized hardware too but your brain has repurposed it to other tasks. You have to train yourself to do social interaction, and you can get pretty good at it. The people who have it implemented in hardware, however, unconsciously employ a series of tests to determine whether you're ingroup or outgroup. Some of these tests are timing-based and you will flunk if you cannot produce the correct social response at the correct time. Difficult to do unless you're hardwired with their ingroup's form of social programming.