Hunter Holly, Blackburn Grace, Ashton Benjamin J, Ridley Amanda R
Centre of Evolutionary Biology, School of Biological Sciences, University of Western Australia, Perth, WA, Australia.
College of Science and Engineering, Flinders University, Adelaide, SA, Australia.
Anim Cogn. 2025 May 26;28(1):41. doi: 10.1007/s10071-025-01963-0.
Animals may benefit from the ability to discriminate between quantities in their environment; for example, when choosing between foraging patches differing in food availability or assessing the size of rival groups. Numerous studies utilising spontaneous quantity discrimination tasks have found that a wide range of species possess the ability to discriminate between quantities, with large interspecific differences being found in these capabilities. However, the causes of variation in quantity discrimination have received less attention, particularly when considering intraspecific variation. Here, we use a spontaneous quantity discrimination task to (i) investigate if Western Australian magpies possess quantity discrimination abilities, and (ii) determine the factors that underlie individual variation in this ability. We found that magpies were able to discriminate between two discrete quantities of a food reward and chose the larger quantity of food more often than expected by chance, with their accuracy increasing as the difference between the two quantities of food items increased (i.e. as the ratio decreased). Individual performance on the assay was significantly affected by group size, with individuals from smaller groups choosing the larger quantity of food more often than individuals from larger groups when presented with the 2 vs. 5 combination. This group size difference may arise because individuals from smaller groups benefit more from enhanced quantity discrimination abilities compared to individuals from larger groups due to the greater risk of competition and loss of resources from intergroup conflict with larger groups. Our study is the first to investigate and identify group size as a source of intraspecific variation in spontaneous quantity discrimination abilities and highlights the importance of considering the causes of individual variation in cognitive performance.
动物可能会从辨别环境中数量的能力中受益；例如，在不同食物可获得性的觅食区域之间进行选择，或评估竞争群体的规模时。许多利用自发数量辨别任务的研究发现，广泛的物种都具备辨别数量的能力，并且在这些能力上发现了很大的种间差异。然而，数量辨别差异的原因受到的关注较少，尤其是在考虑种内差异时。在这里，我们使用自发数量辨别任务来：（i）调查西澳大利亚喜鹊是否具备数量辨别能力，以及（ii）确定这种能力个体差异的潜在因素。我们发现喜鹊能够辨别两种不同数量的食物奖励，并且比随机预期更频繁地选择数量更多的食物，随着两种食物数量之间的差异增加（即比例降低），它们的准确率也会提高。在该试验中，个体表现受到群体规模的显著影响，当呈现2对5的组合时，来自较小群体的个体比来自较大群体的个体更频繁地选择数量更多的食物。这种群体规模差异可能是因为与来自较大群体的个体相比，来自较小群体的个体从增强的数量辨别能力中受益更多，这是由于与较大群体的群体间冲突导致竞争加剧和资源损失的风险更大。我们的研究首次调查并确定群体规模是自发数量辨别能力种内差异的一个来源，并强调了考虑认知表现个体差异原因的重要性。
