False alarm: a reply to Over and Evans

Strength of Belief Guides Information Foraging

Theories of how people value and search for information share the assumption that beliefs give rise to the perceived value of information. However, few studies have directly addressed the pre-search processes that influence information-foraging behavior. This experiment examined the influence of pre-search belief updating on the perceived value of information sources. A sample of college students completed a hypothesis-testing, medical-diagnosis task. The experiment used medical tests with equal objective informative value before unveiling a presenting symptom intended to alter the strength of belief in different disease hypotheses. The observed patterns of test selection suggest that changes in beliefs about disease hypotheses result in systematic and predictable changes in test preference-a notion we refer to as the principle of hypothesis-guided search. We also present a simulation of how pre-search processes (e.g., hypothesis generation and working memory capacity) and task variables (e.g., time pressure) influence subsequent information search.

Confirmation Bias: A Ubiquitous Phenomenon in Many Guises

Confirmation bias, as the term is typically used in the psychological literature, connotes the seeking or interpreting of evidence in ways that are partial to existing beliefs, expectations, or a hypothesis in hand. The author reviews evidence of such a bias in a variety of guises and gives examples of its operation in several practical contexts. Possible explanations are considered, and the question of its utility or disutility is discussed.