I have a theory about some faults thats rather harsh, but hear me out:
I think that the people who ‘cant pick up on signals’ are somewhat selfish/self-absorbed. Now, they probably don’t believe they are, because they aren’t doing anything that they consider selfish. But in the course of dating my fiancee, I’ve certaintly learned things that made me understand (and address) my faults better.
A lot of us (especially us nerds) develop a very deep, intense interest in a hobby. Its our primary activity, we like hanging out with people who share the activity, learning more about it, etc. Some people enjoy it, and enjoy sharing their intrest in it. This leads to monopolizing conversations with people. You spend so much time talking about yourself and what you like and what you are passionate about it kind of eclipses the other person. Many times, if you let the person get a word (or ten) in edgewise, you can actively listen to them and be able to gauge their interest. I know that when I get shy I can’t freaking shut up, I’m like a motormouth, and not surprisingly I won’t be able to remember a damn thing about the other person later.
Active listening is really important. It means asking questions and helping the other person feel engaged. This has two benefits- you make yourself seem more interesting/show empathy, and you really learn a lot about the other person. Purely anecdotal, but I observed a pattern with people who couldn’t pick up on signals- they tended to take things really literally, they had a hard time with sarcasm, or all those millions of stupid little cues we need to know (when you’re lingering at a guests home too long, when you are in someone’s personal space, etc etc).
Another thing about it is shyness. A lot of us are terrified of rejection, maybe we got bullied and developed hang ups about it. I liked online dating because I felt I had a lot less to lose by being bold and assertive- if the woman was offended, splashed her drink in my face and stormed out, no big deal; we don’t really know each other, its not as awkward as dating a friend and having it crash and burn. However, more often than not this confidence and assertiveness paid off. But people that ‘miss signals’ are often afraid to take the risk. They’re afraid to be embarassed or humiliated. They don’t think the person could possibly show interest in them.
To any of those who are shy/socially awkward, I say try and step out of your comfort zone, tell yourself “I don’t care if this backfires horribly”. I don’t wring my hands that I’m gonna get a crappy Big Mac at Mcdonands, and I don’t wring my hands that my date is not going to like me. I think when you can reach this point, you see some positive benefits and it makes it easier and easier to continue to be more confident.