I'd tell them to organise a team building day if they want you to talk to each other. You're there to work, not chat. I don't know what your co-workers are like or what your view on being friends with colleagues obviously but if you're not the type of person to talk about your personal life at work (which is fair enough) then what are you supposed to talk about? Talking about how somebody's kid drew a dog would send me over the edge. There's a line that varies from person to person over how much they reveal to their co-workers and I find it insulting that your boss thinks you have to talk about your boyfriend or kids in order to do your job.