When faced with two competing hypotheses, people sometime prefer to look at multiple sources of information in support of one hypothesis rather than to establish the diagnostic value of a single piece of information for the two hypotheses. This is termed pseudodiagnostic reasoning, and is understood to reflect a pervasive confirmation bias. Past research suggests that diagnostic reasoning may be more easily fostered when participants seek data to help in the selection of one of two competing courses of action as opposed to situations where they seek data to help inferring which of two competing hypotheses is true. In the experiment reported here, we provide the first empirical evidence demonstrating that the facilitating effect observed in action problems is driven by considerations of information relevance, reasoners’ motivations and the numerical value of the first piece of information presented. The discussion of these findings focuses on implications for the ability to engage in diagnostic hypothesis-testing.