[O4] 口頭4 《社会的認知》

[O4-05] Hindsight bias on muddiness judgment of water and probability judgement of flush flood

An experiment for the testimony at a trial

*Hiroshi Yama¹, Masashi Akita², Takuya Kawasaki² (1. Osaka City University, 2. Law Office of Shin-Yu)

Keywords:Hindsight bias, Probability judgment, Trial case

Three kinder garden teachers took some kids to a river side, a flash flood occurred, and a kid died. The focus was that if the accused could have predicted the flash flood. This experiment was conducted to test if people are susceptible to hindsight bias in this trial case. University students were presented four pictures actually taken before the flash flood and were asked to rate how muddy the river looks on 7-point scale and to infer the probability of flash flood from the muddiness. The participants in the outcome group were instructed that a flash flood was actually occurred and there were victims. Those in the outcome condition judged that the river was muddier and the probability of flood was higher than those in the control condition. We concluded that it is plausible that people are susceptible to hindsight bias on perceptual and probability judgment.