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We have a new paper out in Behavioural Processes, as part of a special issue on cognition in fish. You can read the full paper here, and here’s the legend for the schematic above, and abstract below that:

Figure legend: Ways in which individuals in larger groups can make better decisions than individuals or smaller groups. Individuals are represented by circles, and the flow of information by arrows from the source to the recipient. (a) When there is individual-level improvement of cognitive ability, there is no flow of information between individuals. Instead, being in a group reduces the perception of predation risk, allowing individuals to allocate more cognitive resources into other tasks, or vigilance for predators where risk is not (or less) affected by prey group size. (b) Information can be centralised from all or some group members, where it is processed and either an overall group decision is made, or the information is made available to group members to use. (c) In the case of leadership, information flows from a single (or a few) individual(s) with pertinent knowledge to other group members. (d) Only in swarm intelligence is there information flow and no obvious key individual that centralises or leads. Note that for illustration, (a-d) show extreme cases. In the case of house-hunting ants for example, swarm intelligence occurs via self-organised interactions between scout ants (as in (d), but which are only a subset of the whole colony), and once a decision is made, the rest of the colony is led (c) by these individuals to the new nest site (Franks et al., 2003). Similarly, these processes are not mutually exclusive even at the same time. In a foraging group of birds (Morand-Ferron and Quinn, 2011), for example, individuals may have improved foraging due to a reduced perception of risk (a) and also benefit from the vigilant individual who detected the threat (c). In fish shoals, interactions occur directly between individuals (Ioannou et al., 2011), while in social insects they can be direct, for example resulting in lane formation (Fourcassié et al., 2010; Perna et al., 2012), or indirect, as occurs in trail formation via the deposition of pheromones (Moussaid et al., 2009).

Abstract: Larger groups often have a greater ability to solve cognitive tasks compared to smaller ones or lone individuals. This is well established in social insects, navigating flocks of birds, and in groups of prey collectively vigilant for predators. Research in social insects has convincingly shown that improved cognitive performance can arise from self-organised local interactions between individuals that integrates their contributions, often referred to as swarm intelligence. This emergent collective intelligence has gained in popularity and been directly applied to groups of other animals, including fish. Despite being a likely mechanism at least partially explaining group performance in vertebrates, I argue here that other possible explanations are rarely ruled out in empirical studies. Hence, evidence for self-organised collective (or ‘swarm’) intelligence in fish is not as strong as it would first appear. These other explanations, the ‘pool-of-competence’ and the greater cognitive ability of individuals when in larger groups, are also reviewed. Also discussed is why improved group performance in general may be less often observed in animals such as shoaling fish compared to social insects. This review intends to highlight the difficulties in exploring collective intelligence in animal groups, ideally leading to further empirical work to illuminate these issues.