Ambiguity aversion has been widely observed in individuals’ judgments. Using scenarios that are typical in decision analysis, we investigate ambiguity aversion for pairs of individuals. We examine risky and cautious shifts from individuals’ original judgments to their judgments when they are paired up in dyads.

In our experiment the participants were first asked to specify individually their willingness-to-pay for six monetary gambles. They were then paired at random into dyads, and were asked to specify their willingness-to-pay amount for the same gambles. The dyad’s willingness-to-pay amount was to be shared equally by the two individuals. Of the six gambles in our experiment, one involved no ambiguity and the remaining five involved different degrees of ambiguity. We found that dyads exhibited risk aversion as well as ambiguity aversion. The majority of the dyads exhibited a cautious shift in the face of ambiguity, stating a smaller willingness-to-pay than the two individuals’ average. Our study thus confirms the persistence of ambiguity aversion in a group setting and demonstrates the predominance of cautious shifts for dyads.

System dynamics models are typically used to simulate the behaviour of the problem system under discussion environment, to help understand and solve complex problems. Group model building is a social process for including client groups in the system dynamics modelling process. Recent evidence suggests group model building is useful in supporting durable group decisions by supporting the mental models of participants to become more aligned. There have been several mechanisms proposed to explain these effects. This paper creates a combined model that links the five best-supported mechanisms. The combined model suggests five core conditions of group model building that contributes to its success: completing a structured task, producing a tangible artefact, representing system complexity, the portrayal of causal links, and easy modification or transformation of the artefact by participants. Practitioners are encouraged to use group decision approaches that integrate these conditions.