A group size effect on personal risk judgments: implications for unrealistic optimism.

In Experiments 1 and 2, college students (N = 32 and N = 18, respectively) read heart attack risk profiles (i.e., lists of risk factors) for each of several employees at a series of fictional companies and judged the heart attack risk of the typical employee at each company. In both experiments, subjects' risk judgments increased as a function of the number of employees at the companies. In Experiments 3A and 3B, college students (N = 56 and N = 33, respectively) judged the heart attack risk of the typical employee at a company and also judged the risk of each individual employee. In these experiments, the typical employee was generally judged to be at higher risk than the individual employees. This group size effect might help to explain unrealistic optimism--people's tendency to judge themselves to be at lower risk than their peers for negative life events. Furthermore, it can be modeled successfully within Fiedler's (1996) BIAS framework.