Subjects participating in Wason's rule discovery task (1960) overwhelmingly try to confirm rather than refute their currently held hypothesis. Such a strategy is often inadequate and runs counter to the canons of scientific methodology. The present study was designed to investigate subjects’ differential evaluation of test strategies and outcome. One-hundred and sixty students participated in two experiments in which they had to judge someone else's potential test items in Wason's task. Experiment 1 demonstrated that exposure to various histories has a mediating effect on the strength of the confirmation bias. In Experiment 2, subjects knew the researcher's rule and thus whether each proposed test item would lead to confirmation or refutation of the hypothesis under consideration. The preferred items were those that alerted the subject to an incorrect hypothesis (refutation) and those that turned out to be positive instances of the rule sought after, with the combination of the two (a negative test leading to refutation) being most highly evaluated.

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A well-documented characteristic of rule discovery behaviour is subjects’ infrequent use of negative testing. Previous attempts at increasing the use of negative testing have met with little success. In an evaluation task, we found that subjects appreciate the benefits of negative testing and disconfirmation (Kareev & Halberstadt, this issue). Further, when given the choice, subjects prefer to begin their inquiry by employing a reception mode of inquiry, and only later switch to a generative strategy (Halberstadt & Kareev, 1992). In the present study we had subjects solve two rule-discovery problems. For the training problem, 180 subjects were assigned either to the traditional generation mode, in which subjects had to generate number triplets, or to a reception mode, in which subjects were presented with number triplets by the experimenter. For the subsequent test problem both groups used the traditional generation mode. Results revealed that subjects trained by the reception mode were more likely to use non-positive tests and more likely to solve the second problem. Apparently, training under the less demanding reception mode enabled subjects to realize the potential relevance of nonpositive testing.

Scientists obtain their knowledge about the world through one of two major modes of inquiry--observation of naturally occurring phenomena and active experimentation. Both modes of inquiry have been extensively researched in studies of hypothesis testing behaviour and scientific inquiry, the first in studies employing the reception paradigm, the second in studies employing the selection/generation paradigm. The prevalence of both paradigms and their correspondence to well-established modes of scientific inquiry led to the hypothesis that subjects, if allowed, would employ both modes of inquiry. The variables affecting the choice of one mode rather than the other and the transitions between the two modes were expected to shed new light on the process of scientific inquiry. To test this hypothesis, 27 adults and 27 eighth-graders were set three rule-discovery problems, in a computer environment that allowed free transitions between item reception and generation. Item generation was significantly more prevalent in the adult sample, but almost all the adults and approximately half the children employed both modes of inquiry in at least one problem. When both modes of inquiry were employed, the reception mode tended to precede the generation mode. An inverse relationship was observed between item generation and the proportion of positive instances supplied by the environment. Individual inquiry styles were evident in both age groups. These results call attention to the need for a theory incorporating both modes of inquiry as integral components of the inquiry process. They also demonstrate the utility of empirical investigations that let subjects freely choose which mode to employ at any point of the inquiry process.