As for the pet theory, it has to do not with "higher" intelligence but with an idiosyncratic use of attention: a nerd is someone who pays more attention to something than the usual metric of social payoff would indicate, who is distracted from the things that make one easy-going and relatable by things that do not seem to outsiders to merit the effort. Trainspotters. Music nerds (many such hereabouts). Shevek is a perfect example of someone who pays attention to things that, from the point of view of his society, are the wrong things. This happens to overlap with the autistic type because one of the ways that autists manage discomfort and confusion is by absorbing themselves in "special interests", which give order to a small part of the world. Sometimes this is a completely sterile absorption, sometimes it results in specialised knowledge and talents that turn out (as in the case of today's techie nerds) to have a market value that can be exploited, sometimes it can become the basis for a position of status and esteem within a subculture devoted to the object of fascination.