One good trait convinces you a stranger must be good at everything else too

Edward Thorndike found that when military officers rated soldiers on totally unrelated qualities — intelligence, leadership, physique — the scores were all suspiciously correlated. A single strong impression spreads across an entire judgement of a person, which is a big part of why attractive people get rated as more competent.

— Edward Thorndike, A Constant Error in Psychological Ratings — Journal of Applied Psychology, 1920