Effects of judges' forecasting on their later combination of forecasts for the same outcomes

Abstract

In a first experiment, we show that judges' ability to combine forecasts that they receive from more knowledgeable advisors is impaired when they have previously made their own forecasts for the same outcomes. It appears that they implicitly include their own forecasts among those that have to be combined. In a second experiment, we demonstrate that people combining forecasts put more weight on forecasts that are their own (whether or not they are labelled as such) or are labelled as their own (when they are not) than on equivalent forecasts that are neither their own nor labelled as such. We argue that the cognitive mechanisms responsible for these effects are better characterized as a type of conservatism rather than as an example of anchoring. Our results imply that people responsible for integrating forecasts from more knowledgeable advisors should not explicitly include their own forecasts among those that they combine and should consider avoiding making their own forecasts altogether.