ABSTRACT
With hindsight, we tend to exaggerate what we had known in foresight. For example, after the US and British troops attacked Iraq in March 2003 without a further resolution of the United Nations Security Council, we were likely to overestimate how predictable this was (as compared to a prediction made in, say, January). This effect has been termed “hindsight bias” or the “knew-it-all-along” effect. The oldest empirical demonstration of this phenomenon that we are aware of dates back more than 50 years. However, it was only treated as a marginal part of that study, was not given a name, and was only marginally interpreted by the author (Forer, 1949). Things changed when Fischhoff (1975) published his classic paper on the hindsight bias. After this rediscovery, numerous studies were conducted, and it was just 15 years later that Hawkins and Hastie (1990) published an extensive review on the hindsight bias, closely followed by Christensen-Szalanski and Willham’s (1991) meta analysis, which covered 122 studies published in 40 articles. A more recent literature search in Psyc-INFO (up to week 21/2003) with the entry “hindsight bias OR knew it all along” revealed 152 hits. In 5-year intervals, starting in 1975, 1980, 1985, 1990 and 1995, the numbers were 3, 8, 15, 37, and 56, respectively, indicating considerable growth over time. Given the amount of research, it is hardly surprising that this phenomenon is also treated in most textbooks on judgement and decision making, cognitive biases, and memory.
