I got in trouble at work once as an adult for not responding to a client who said "Hi" when passing me in the hall. I honestly never saw/heard the guy... was too busy thinking about solving his messy business problems.

My D is borderline Asperger's (have had testers tell me she probably is, and some say she isn't). I do know that I often have to provide her with very specific social scenarios and responses that wouldn't need to be explained to most people.