One of the most widely applicable benefits of aggregation is a per capita reduction in predation risk. Many factors can contribute to this but, for moving groups, an increased difficulty in tracking and targeting one individual amongst many has received particular attention. This “confusion effect” has been proposed to result from a bottleneck in information processing, a hypothesis supported by both modelling and experiment. If the competition for limited attention is localised to the particular part of the visual field where the target is located, prey density is likely to be the key factor rather than group numbers per se. Furthermore, unpredictability of prey movement may enhance confusion, but both factors have received insufficient attention from empiricists: undoubtedly because of the difficulty of experimental manipulation in natural systems. We used a computer-based target tracking task with human subjects to manipulate effects of number and density independently, in factorial combination with motion path predictability. Density, rather than number, drove the confusion effect in our experiment and acted synergistically with the unpredictability of the direction of motion. The experimental paradigm we present offers the potential for isolating other factors affecting predation success on group-living prey, and forging links with the psychological literature on object tracking and visual search.

中文翻译：

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群体移动：密度和不可预测的运动如何影响捕食风险


聚集最广泛应用的好处之一是人均捕食风险的降低。造成这种情况的因素有很多，但对于移动的群体来说，跟踪和瞄准众多个体中的一个人的难度增加受到了特别关注。这种“混乱效应”被认为是信息处理瓶颈造成的，这一假设得到了建模和实验的支持。如果对有限注意力的竞争局限于目标所在视野的特定部分，那么猎物密度可能是关键因素，而不是群体数量本身。此外，猎物运动的不可预测性可能会加剧混乱，但这两个因素都没有受到经验主义者的足够重视：无疑是因为自然系统中实验操纵的困难。我们对人类受试者使用基于计算机的目标跟踪任务，与运动路径可预测性相结合，独立地操纵数量和密度的影响。在我们的实验中，密度（而不是数量）驱动了混乱效应，并与运动方向的不可预测性协同作用。我们提出的实验范式提供了分离影响群居猎物捕食成功的其他因素的潜力，并与物体跟踪和视觉搜索的心理学文献建立联系。