Probabilities and utilities of fictional outcomes in Wason's four-card selection task.

Four experiments are presented that show that selections in Wason's (1966) four-card selection task can be increased by increasing the probability that cards will yield important outcomes. Experiment 4 also shows that selections can be influenced by varying the utilities of possible outcomes. These results suggest that some important content effects in this task may not arise from inferential processes, and examples are given of how probabilities and utilities have been confounded with other manipulations in previous research. The recent trend towards content-dependent theories of reasoning may have arisen largely because theorists are attempting to construct models of inferential reasoning that can account for what are, in part, non-inferential phenomena. Content-independent inferential processes and content-independent choice processes may operate together to account for content effects in the selection task.