But that's the whole point: it's hard to tell! Of course the classification is easy at the end points (super helpful guy vs total arrogant jerk) but towards the mean the probability of false alarm is much larger. Geeks are a diverse bunch, it may just be that the guy is from another country where interactions are different or it may be just that he's a bit awkward initially because he does not interact with women daily (it happens).

I think the correct approach is to give them the benefit of doubt for a while before labeling them as dudes or whatever. Isn't that the golden rule?