Research on same-different categorization has shown that mastery of tasks of this kind can be strongly affected by the number of items in the training arrays-for both humans and nonhuman animals. Evidence for two-item same-different categorization in pigeons is decidedly mixed: although some investigations have succeeded, others have failed. To date, no research has documented successful conditional same-different categorization using just two items, nor has research explored how pigeons' responses in this paradigm might be influenced by perceptual characteristics of the training stimuli. Through a series of methodological modifications, we provide the first successful documentation that pigeons can perform two-item conditional same-different categorization to a high degree of accuracy; further, they can do so without the support of item repetition. We also show for the first time that the perceptual disparity between the items in pairs of different stimuli plays a key part in pigeons' same-different categorization performance. (PsycInfo Database Record (c) 2021 APA, all rights reserved).

中文翻译：

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鸽子中的两项条件相同-不同分类：发现差异。

对相同-不同分类的研究表明，对于人类和非人类动物，训练数组中的项目数量会极大地影响对此类任务的掌握。鸽子中两个项目相同-不同分类的证据显然是混合的：尽管一些调查成功了，但其他调查失败了。迄今为止，没有研究记录了仅使用两个项目成功的条件相同-不同分类，也没有研究探索鸽子在这种范式中的反应如何受到训练刺激的感知特征的影响。通过一系列方法上的修改，我们提供了第一个成功的文件，证明鸽子可以高度准确地执行两项条件同异分类；更远，他们可以在没有项目重复的支持的情况下这样做。我们还首次表明，不同刺激对中项目之间的感知差异在鸽子的相同-不同分类表现中起着关键作用。（PsycInfo 数据库记录 (c) 2021 APA，保留所有权利）。