A judgemental bias that tends to affect people's subjective estimates of the likelihood of future events in their lives, causing them to overestimate the likelihood of positive or desirable events and to underestimate the likelihood of negative or undesirable events. It was first reported in 1925 by the US psychologist F(rederick) H(ansen) Lund (1894–1965) and in 1938 by the US psychologist (Albert) Hadley Cantril (1906–69), and it came to prominence in 1980 when it was studied rigorously and named by the US psychologist Neil D(avid) Weinstein (born 1945) in an article in the Journal of Personality and Social Psychology. Weinstein asked students to estimate the relative likelihoods of various events happening to them, compared to the likelihoods of the same events happening to their peers, and his results showed that they rated their chances of experiencing positive events, such as owning your own home, receiving a good job offer before graduation, and living past 80, to be significantly above the average for students of the same sex at the same university, and their chances of experiencing negative events, such as having a heart attack before age 40, being sued by someone, and being the victim of a mugging, to be significantly below average. See also depressive realism, hypomanic episode. Compare Lake Wobegon effect, overconfidence effect.