THE EFFECTS OF NEW INFORMATION - PERSEVER ANCE AND HINDSIGHT

The perseverance effect refers to the phenomenon that people overestim ate the probability of a given event after having been asked to give r easons for the occurence of this event. This happens even if they are informed that no information actually exists about whether the event r eally occurred. The hindsight bias, or knew-it-all-along-effect, on th e other hand describes the phenomenon that people immediately assimila te what they previously thought about the probability of an event once they have been informed whether the event really did take place or no t. This paper presents an experiment which added manipulations used in traditional hindsight research to a research design testing the perse verance phenomenon. Both phenomena - the perseverance effect and the h indsight bias - were replicated under specific conditions: After the s ubjects had given reasons for a given event only the information that another event had actually occurred affected their probability judgmen ts (hindsight conditon), whereas the information that nothing was actu ally known about the occurrence of the event did not affect the probab ility judgments (perseverance condition).