Different species show an intriguing similarity in representing numerosity in space, starting from left to right. This bias has been attributed to a right hemisphere dominance in processing spatial information. Here, to disentangle the role of each hemisphere in dealing with spatial versus ordinal–numerical information, we tested domestic chicks during monocular versus binocular vision. In the avian brain, the contralateral hemisphere mainly processes the visual input from each eye. Four‐day‐old chicks learned to peck at the fourth element in a sagittal series of 10 identical elements. At testing, chicks faced a left‐to‐right–oriented series where the interelement distance was manipulated so that the third element was where the fourth had been at training; this compelled chicks to use either spatial or ordinal cues. Chicks tested binocularly selected both the fourth left and (to a lesser extent) right elements. Chicks tested monocularly chose the third and fourth elements on the seeing side equally. Interhemispheric cooperation resulted in the use of ordinal–numerical information, while each single hemisphere could rely on spatial or ordinal–numerical cue. Both hemispheres can process spatial and ordinal–numerical information, but their interaction results in the supremacy of processing the ordinal–numerical cue.

中文翻译：

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一天大的家养小鸡（Gallus gallus）的空间与顺序处理的半球专业化

从左到右，不同的物种在表示空间数量方面表现出有趣的相似性。这种偏差归因于右半球在处理空间信息方面的优势。在这里，为了弄清每个半球在处理空间信息与顺序数字信息方面的作用，我们在单眼与双眼视觉下测试了家养小鸡。在鸟类大脑中，对侧半球主要处理来自每只眼睛的视觉输入。四天大的小鸡学会了啄食一组 10 个相同元素的矢状序列中的第四个元素。在测试中，小鸡面临着一个从左到右的系列，其中元素间的距离被操纵，因此第三个元素是第四个元素在训练中的位置；这迫使小鸡使用空间或顺序线索。测试的小鸡双目选择了第四个左侧和（在较小程度上）右侧的元素。单眼测试的小鸡平等地选择了观察侧的第三和第四元素。半球间合作导致使用序数-数字信息，而每个半球都可以依赖空间或序数-数字提示。两个半球都可以处理空间和序数信息，但它们的相互作用导致处理序数线索的优势。