Kelly E McKenna
Department of Neurobiology and Behavior, Cornell University, Seeley G. Mudd Hall, 215 Tower Road, Ithaca, NY 14853, USA.
Behav Processes. 2016 Jul;128:9-16. doi: 10.1016/j.beproc.2016.03.019. Epub 2016 Mar 29.
Quantity discrimination has been established in a range of species. However, most demonstrations of quantity discrimination control for social factors by testing animals individually. I tested whether sociality affects quantity discrimination in the wild by comparing the performances of the highly social Mexican jay (MJ; Aphelocoma wollweberi) and the territorial Western scrub jay (WJ; Aphelocoma californica). The birds were given a choice between two lines of peanuts that differed in initial quantity ranging from 2 vs 8 to 14 vs 16. Their choices were recorded until all peanuts were eaten or cached. Whereas non-social WJ selected the larger quantity across all the trials significantly more than chance, social MJ selected the larger line only when the difference in the number of peanuts between lines was small. In MJ, individual choice when selecting the large or small quantity was influenced by what line the previous bird had chosen when the difference in lines was large, with followers significantly more likely to select the smaller quantity. WJ were not significantly affected by the choices of other individuals. The only factors that influenced WJ choice were ratio and total differences between the two quantities. These results suggests that in certain scenarios, both species can discriminate between different quantities. However, MJ were greatly influenced by social factors, a previously untested factor, while WJ were only influenced by ratio and total difference between the quantities, consistent with findings in other species. Overall, this study demonstrates the important role of sociality in numerical cognitive performance, a previously overlooked factor.
数量辨别在一系列物种中都已得到证实。然而，大多数数量辨别实验都是通过单独测试动物来控制社会因素的。我通过比较高度群居的墨西哥松鸦（MJ；Aphelocoma wollweberi）和具有领地意识的西部灌丛松鸦（WJ；Aphelocoma californica）的表现，来测试群居性是否会影响野生环境中的数量辨别。给这些鸟提供两排花生供其选择，两排花生的初始数量不同，范围从2对8到14对16。记录它们的选择，直到所有花生都被吃掉或储存起来。非群居的WJ在所有试验中选择数量较多那排的次数显著高于随机概率，而群居的MJ只有在两排花生数量差异较小时才会选择数量较多的那排。在MJ中，当两排花生数量差异较大时，个体选择大数量或小数量会受到前一只鸟选择的影响，跟随者选择较小数量的可能性显著更高。WJ不受其他个体选择的显著影响。影响WJ选择的唯一因素是两数量之间的比例和总数差异。这些结果表明，在某些情况下，这两个物种都能区分不同的数量。然而，MJ受到社会因素的极大影响，这是一个此前未被测试过的因素，而WJ只受到数量之间比例和总数差异的影响，这与其他物种的研究结果一致。总体而言，这项研究证明了群居性在数字认知表现中的重要作用，这是一个此前被忽视的因素。
