The induction of rules by making queries is a dynamical process based on seeking information. Experimenters typically look for one dominant strategy that is used by subjects, which may or may not agree with normative models of this psychological process. In this study we approach this problem from a different perspective, related to work in learning theory (see for example Baum 1991, Freund et al. 1995). Using information theory in a Bayesian framework, we estimated the information gained by queries when the task is to find a specific rule in a hypothesis space. Assuming that at each point subjects have a preferred working hypothesis, we considered several possible strategies, and determined the best one so that information gain is maximized at each step. We found that when the confidence in the preferred hypothesis is weak, "Confirmation Queries" result in maximum information gain; the information gained by "Investigation Queries" is higher when the confidence in the preferred hypothesis is high. Considering the dynamical process of searching for the rule, starting with low confidence in the preferred hypothesis and gradually raising confidence, there should be a transition from the "Confirmation Strategy" to the "Investigative Strategy", as the search proceeds. If we assume that subjects update their beliefs regarding the task, while performing, we would expect that the "Positive Confirmation Strategy" would yield more information at low confidence levels while the "Negative Confirmation Strategy" (simple elimination) would be more informative at higher confidence levels.

We tested subjects performance in such a task, using a paradigm introduced by Wason (1960). All subjects first assumed a hypothesis and then made positive confirmation queries. Upon receiving confirmation, half the subjects presented negative confirmation queries and later, half switched into investigative queries before attempting to guess the experimenter's rule. Also, the frequency of queries in the more 'advanced' strategies went down as the confidence level required to evoke the strategy went up. We conclude that subjects appear to be using different strategies at different stages of the search, which is theoretically optimal when queries are guided by a paradigm that maximizes information gain at each step.