Recruiters look at many particular signs in a candidate and draw conclusions that, sometimes, look shallow, sometimes odd.
To begin with, very few companies have employees that do interviewing full time. For almost every recruiter and interviewer you meet, you encounter someone who might range from
an interview once a year to
never before meeting you, to
interviews many people every day.
Very few companies use structured intereviewing to recruit candidates. You are more likely to encounter technique in phone surveys, or in the computer-based personality tests that many retailers and entry level companies screen applicants with (read Punchinin In for more details). Typically retail companies have to hire lots of staff due to high turnover, so they have a vested interest in determining what sort of personality does well, and what fits badly. This means that the sort of person who would do well at Home Depot for example, is very likely to do poorly at Abercrombie Fitch; both stores have wildly different customer bases and product lines.
More and more intereviewers appear to be using competency based interviewing. These are less about the details of what you know, and more about how you think and solve problems. For people who memorize a lot of things, these sort of interviews are very hard to pass.
One of my pet research areas is in decisionmaking. People do not make decisions in logical, repeatable manners. Interviewing and recruiting employees is just another example of this human foible. For an introduction to why this is the case, I recommend 3 books:
Sources of Power. This book describes a new theory of decisionmaking (recognition primed decision) that claims you recognize patterns in previous instances and use those memories to make decisions.
Predictably Irrational. The author does research in behavioral economics. So this book is a summary of some of the research he and his colleagues have done on how people make decisions that make perfect sense at the time yet are quite irrational from the economic concept of "rational consumer."
Checklist Manifesto. Our lives are rather complicated, and we tend to forget things at inconvenient times, especially when things are framed in particular manners (advertising and politics use framing to divert your attention from what is important to you).