The domain specificity and generality of disjunctive reasoning: Searching for a generalizable critical thinking skill.

The domain specificity and generality of an important critical thinking skill was examined by administering 9 reasoning and decision-making tasks to 125 adults. Optimal performance on all of the tasks required that disjunctive processing strategies—strategies requiring the exhaustive consideration of all of the possible states of the world—be adopted. Performance across these disjunctive reasoning tasks displayed considerable domain specificity, but 5 of the tasks displayed moderate convergence. Cognitive ability was associated with performance on only 3 of 9 tasks. Six of the 9 tasks displayed associations with 1 of 2 cognitive styles that were examined in the multivariate task battery (need for cognition and reflectivity). Performance on the 5 tasks that displayed some domain generality was also more associated with thinking styles than with cognitive ability in several regression analyses. In an important article on the cognitive processes that underlie performance on many thinking and reasoning tasks, Shafir (1994) emphasized the importance of a fully disjunctive approach to decision-making and problem-solving situations. Shafir defined this disjunctive reasoning skill as the tendency to consider all possible states of the world when deciding among options or when choosing a problem solution in a reasoning task. Most decisionmaking situations can be thought of as disjunctions of possible states of the world. Thus, choosing optimally entails combining the probabilities of the states with the desirabilities of the outcomes under each of the decision options (Jeffrey, 1983; Savage, 1954). Many problem-solving situations can likewise be optimally evaluated by constructing all of the mental models that are consistent with the premises as presented (Johnson-Laird, 1983, 1999; Johnson-Laird & Byrne, 1991). Despite the seeming obviousness of disjunctive reasoning as a general thinking strategy, Shafir (1994) demonstrated how, if one looks across the wide domain of reasoning tasks used in cognitive science, it is easy to find tasks in which people perform suboptimally because they do not use the strategy. Consider one of the simplest applications of the disjunctive reasoning strategy—that embodied in the sure-thing principle in Savage’s (1954) seminal derivation of the axioms of expected utility theory. Imagine you are choosing between two possible outcomes, A and B, and event X is an event that may or may not occur in the future. If you prefer prospect A to prospect B if X happens and you also prefer prospect A to prospect B if X does not happen, then you definitely prefer A to B. A disjunctive consideration of the alternative states of the world (either X will occur or not) should lead to the conclusion that uncertainty about whether X will occur or not should have no bearing on your preference. Because your preference is in no way changed by knowledge of event X, you should prefer A to B whether you know anything about event X or not.