Asynchrony rescues statistically-optimal group decisions from information cascades through emergent leaders

It is usually assumed that information cascades are most likely to occur when an early but incorrect opinion spreads through the group. Here we analyse models of confidence-sharing in groups and reveal the opposite result: simple but plausible models of naïve Bayesian decision-making exhibit information cascades when group decisions are synchronous; however, when group decisions are asynchronous, the early decisions reached by Bayesian decision makers tend to be correct, and dominate the group consensus dynamics. Thus early decisions actually rescue the group from making errors, rather than contribute to it. We explore the likely realism of our assumed decision-making rule with reference to the evolution of mechanisms for aggregating social information, and known psychological and neuroscientific mechanisms. Press release Decision-makers often take into account social information from others in their group. When an information cascade happens, the decision of a single individual triggers a chain reaction where most of the group follows the same decision rather than using evidence personally acquired. It is usually assumed that information cascades are most likely to occur when an early but incorrect opinion spreads through the group. Our simulations, based on known psychological and neuroscientific mechanisms, reveal the opposite: erroneous information cascades happen when group decisions are synchronous; however, when group decisions are asynchronous, the early decisions tend to be correct, and dominate the group consensus. Thus early decisions actually rescue the group from making errors, rather than contributing to it, showing how group leaders can spontaneously emerge for the benefit of collective decisions.