Abstract
Previous studies on hypothesis-testing behaviour have reported systematic preferences for posing positive questions (i.e., inquiries about features that are consistent with the truth of the hypothesis) and different types of asymmetric questions (i.e., questions where the hypothesis confirming and the hypothesis disconfirming responses have different evidential strength). Both tendencies can contribute - in some circumstances - to confirmation biases (i.e., the improper acceptance or maintenance of an incorrect hypothesis). The empirical support for asymmetric testing is, however, scarce and partly contradictory, and the relative strength of positive testing and asymmetric testing has not been empirically compared. In four studies where subjects were asked to select (Experiment 1) or evaluate (Experiments 2-4) questions for controlling an abstract hypothesis, we orthogonally balanced the positivity/negativity of questions by their symmetry/asymmetry (Experiments 1-3), or by the type of asymmetry (confirmatory vs disconfirmatory; Experiment 4). In all Experiments participants strongly preferred positive to negative questions. Their choices were on the other hand mostly unaffected by symmetry and asymmetry in general, or - more specifically - by different types of asymmetry. Other results indicated that participants were sensitive to the diagnosticity of the questions (Experiments 1-3), and that they preferred testing features with a high probability under the focal hypothesis (Experiment 4). In the discussion we argue that recourse to asymmetric testing - observed in some previous studies using more contextualized problems - probably depends on context-related motivations and prior knowledge. In abstract tasks, where that knowledge is not available, more simple strategies - such as positive testing - are prevalent.