Pratfall Effect
The tendency for attractiveness to increase or decrease after an individual makes a mistake, depending on the individual's perceived ability to perform well in a general sense.
Origin
Social psychologist Elliot Aronson demonstrated the effect in a 1966 study at the University of Minnesota, published as "The Effect of a Pratfall on Increasing Interpersonal Attractiveness" in Psychonomic Science. Forty-eight students listened to recordings of quiz show auditions in which a high-scoring contestant who spilled coffee was rated most likable. Aronson, who trained under Leon Festinger at Stanford, hypothesized that blunders humanize an otherwise intimidatingly competent person.
Everyday Use
When a brilliant colleague spills coffee during a presentation, they suddenly seem more likable — more human. But if the office underperformer does the same thing, it just confirms the impression that they can't get anything right. The effect only works for people already seen as competent; for everyone else, a blunder is just a blunder.