[Strategies of clinical hypothesis testing]

This research examines whether Psychology students, when they test clinical hypotheses, follow either confirmatory or disconfirmatory reasoning strategies. Two hundred and six psychology students, divided in four groups, participated. One group received information about the probability that the hypothesis was correct by means of verbal labels, and another group, by means of numerical expressions. An additional group received the information that getting a precise diagnosis was clinically important. In a last group, diagnostic tests allowed them to increase certainty about the hypothesis. Results show a partial use of confirmatory strategies because, although participants did not seek confirming information, they indeed avoided collecting disconfirming information. When the information increased certainty about the hypothesis, confirmatory strategies became more likely. Neither the increase in the task importance nor the numerical expression of the likelihood that the hypothesis was correct seemed to affect the testing strategy used.