Date of Award


Degree Type


Degree Name

Doctor of Philosophy in Psychology



First Advisor

W. Grant Willis


The hindsight bias refers to the tendency of people, after an event, to overestimate how accurately they would have predicted the outcome had they been asked in advance. The consequences of the hindsight bias on clinical decision making are significant. The bias is believed to impede one's ability to learn from experience and to lead to an undue level of confidence in future decision making. Research has shown that, under some conditions, groups have been shown to be less susceptible to bias than individual decision makers. The hindsight bias also has been found to be attenuated under certain conditions involving an increase in cognitive effort. The current investigation sought to answer the following questions: (a) Will groups demonstrate less hindsight bias in their decision making efforts than individuals?, and (b) Can the hindsight bias be reduced in groups similar to previous results among individual decision makers? Undergraduate students (N = 180) read two case vignettes, either as individuals or in groups and predicted outcome probabilities, either with the· benefit of outcome information or without. Half of the participants provided with outcome information were also asked to complete a counterfactual reasoning task. Data were analyzed using the binomial sign test and with multivariate analyses of covariance statistics (MANCOVA) with deliberation time included as a potential covariate. Nonparametric analyses indicated that groups were just as susceptible to the hindsight bias as individuals. The hindsight bias could not be eliminated using a counterfactual reasoning task. Implications of the results are discussed along with suggestions for future research.



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