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How do people utilize information from outside sources in their decisions? Participants observed a signal-plus-noise or noise-alone event and then made a yes-no decision about whether a signal had occurred. Participants were provided with two information sources to aid decision making. Each source consisted of four components that provided estimates of signal likelihood. In Experiment 1, the two sources had equal overall accuracy but differed in the expertise and internal correlation of their components. A regression analysis indicated that participants overweighed the high-expertise-highcorrelation source. This bias occurred on trials when the aggregate opinions of the sources disagreed. In Experiment 2, both the overall accuracy of the source and its components were manipulated. Participants overweighed information from the higher accuracy source. These biases reflect people's sensitivity to across-trial and within-trial differences in the accuracy and internal consistency of information sources. Experiment 3 provided additional evidence supporting these conclusions. Copyright # 2004 John Wiley & Sons, Ltd. key words decision weights; decision bias; information sources; belief updating; evidence weightingPeople often make decisions using information and advice from other sources. For example, imagine that you are CEO of a firm that manufactures several lines of children's clothing. Your firm has been considering introducing a completely new product line. In addition to the obvious risks, such a move would involve a sizable commitment in advertising and other expenses for your company. You have asked two marketing consulting firms to assist you in that decision. Firms A and B each study the question and make separate presentations. The first presentation is made by four experts from Firm A. These experts arrive separately at your office and provide a varied set of views and predictions. Their recommendation, while not unanimous, is to postpone the decision for a year. The next day, Firm B's experts make their recommendation. They arrive together and their presentations seem more rehearsed than A's and are consistent with each other.

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