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Publication - Dr Roland Baddeley

    The Bayesian Superorganism III: externalised memories facilitate distributed sampling


    Hunt, ER, Franks, NR & Baddeley, RJ, 2018, ‘The Bayesian Superorganism III: externalised memories facilitate distributed sampling’. bioRxiv.


    A key challenge for any animal is to avoid wasting time by searching for resources in places it has already found to be unprofitable. This challenge is particularly strong when the organism is a central place forager - returning to a nest between foraging bouts - because it is destined repeatedly to cover much the same ground. Furthermore, this problem will reach its zenith if many individuals forage from the same central place, as in social insects. Foraging performance may be greatly enhanced by coordinating movement trajectories such that each ant visits separate parts of the surrounding (unknown) space. In this third of three papers, we find experimental evidence for an externalised spatial memory in Temnothorax albipennis ants: chemical markers (either pheromones or cues such as cuticular hydrocarbon footprints) that are used by nestmates to mark explored space. We show these markers could be used by the ants to scout the space surrounding their nest more efficiently through indirect coordination. We also develop a simple model of this marking behaviour that can be applied in the context of Markov chain Monte Carlo methods (see part two of this series). This substantially enhances the performance of standard methods like the Metropolis-Hastings algorithm in sampling from sparse probability distributions (such as those confronted by the ants) with little additional computational cost. Our Bayesian framework for superorganismal behaviour motivates the evolution of exploratory mechanisms such as trail marking in terms of enhanced collective information processing.

    Full details in the University publications repository