Tomonaga Masaki
Section of Language and Intelligence, Primate Research Institute, Kyoto University, Inuyama, Aichi 484-8506, Japan.
Anim Cogn. 2008 Jan;11(1):43-57. doi: 10.1007/s10071-007-0089-0. Epub 2007 Apr 19.
Two adult chimpanzees were trained on a relative "numerosity" discrimination task. In each trial, two arrays containing different numbers of red dots were presented on a CRT monitor. The subjects were required to choose the array containing the larger number of dots. In Experiment 1, using numerosities between 1 and 8, 28 different pairs were presented repeatedly, and accuracy scores were analyzed to explore which cues the chimpanzee subjects utilized to perform the task. Multiple regression analyses revealed that the subjects' performance was (1) not simply controlled by the "numerical" difference between arrays, but that it was (2) best described by Fechner's Law-that is accuracy increased linearly with the logarithmic value of the numerical difference between arrays divided by the number in the larger of the two arrays. This relationship was maintained when using much larger numerosities (Experiment 3). In Experiment 2, the chimpanzees were tested on the effects of total area and density by manipulating dot size and presentation area. The results revealed that these factors clearly affected the subjects' performance but that they could not alone explain the results, suggesting that the chimpanzees did use relative numerosity difference as a discriminative cue.
对两只成年黑猩猩进行了一项关于相对“数量”辨别任务的训练。在每次试验中，阴极射线管显示器上会呈现两个包含不同数量红点的阵列。要求受试者选择包含较多点数的阵列。在实验1中，使用1到8之间的数量，重复呈现28对不同的阵列，并分析准确率得分，以探究黑猩猩受试者执行任务时利用了哪些线索。多元回归分析表明，受试者的表现：（1）并非简单地受阵列之间“数字”差异的控制，而是（2）用费希纳定律能最好地描述——即准确率随着阵列之间数字差异的对数值除以两个阵列中较大阵列的数字数量而线性增加。当使用大得多的数量时（实验3），这种关系依然成立。在实验2中，通过操纵点的大小和呈现面积，测试了黑猩猩对总面积和密度的影响。结果表明，这些因素明显影响了受试者的表现，但它们并不能单独解释结果，这表明黑猩猩确实将相对数量差异用作辨别线索。
