Taking the sting out of choice: Diversification of investments

It is often the case that one can choose a mix of alternative options rather than have to select one option only. Such an opportunity to diversify may blunt the risk involved in all-or-none choice. Here we investigate repeated investment decisions in two-valued options that differ in their riskiness, looking for the effects of recent decisions and their outcomes on upcoming decisions. We compare these effects to those evident in all-or-none choice between the same risky options. The “state of the world”, namely, the likelihood of the high versus the low outcomes of the options, is manipulated. We find that aggregate allocation diverges from uniformity (i.e., from 1/n), and is sensitive to outcome probabilities, with the pattern of results indicating reactivity to the outcome of the previous decision. Round-to-round dynamics reveal that the outcome of the previous decision has an effect on the subsequent decision, on top of inertia; the aspects of the outcome that influence the next decision indicate an effect of a missed opportunity, if there was one, in the previous decision. Importantly, recent outcomes have a similar effect in diversification decisions and in all-or-none choice.