Preverbal infants represent the approximate numerosity of visual and auditory arrays: By 6 months old, they reliably discriminate eight dots or tones from 16 (a 1:2 ratio), but not eight from 12 (a 2:3 ratio). The precision of this approximate number sense improves gradually over childhood and into adulthood. However, less is known about numerical abilities in younger infants, and in particular, whether there is developmental change in the number sense in the first half year of life. Here, in four experiments, we measured numerical precision in 4‐month‐old infants (N = 128) using a visual habituation task comparable to that in studies of older infants. We found that 4‐month‐olds exhibited poorer numerical discrimination than the 6‐month‐olds tested in previous studies, dishabituating to a 1:4 change in numerical ratio, but not a 1:3 change. Like older infants, 4‐month‐olds’ numerical precision improved when they were provided with redundant visual and auditory input; when both visual and auditory information were present, 4‐month‐olds discriminated a 1:3 but not a 1:2 ratio. These results suggest that Approximate Number System precision develops in early infancy and may be sensitive to intersensory redundancy as early as four months of age.

中文翻译：

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4个月婴儿数值敏锐度的动态变化

会说话的婴儿代表了视觉和听觉阵列的大致数量：到 6 个月大时，他们可以可靠地从 16（1:2 的比例）中辨别出 8 个点或音调，但不能从 12（2:3 的比例）中辨别出 8 个点或音调。这种近似数感的精确度在童年和成年期逐渐提高。然而，对于年幼婴儿的数字能力，特别是生命前半年数感是否有发展变化，我们知之甚少。在这里，在四个实验中，我们测量了 4 个月大婴儿的数值精度 ( N = 128) 使用与大婴儿研究相当的视觉习惯任务。我们发现 4 个月大的婴儿比之前的研究中测试的 6 个月大的婴儿表现出更差的数字辨别力，数字比例的变化是 1:4，而不是 1:3 的变化。与大一点的婴儿一样，4 个月大的婴儿在获得冗余的视觉和听觉输入后，他们的数字精度会提高；当视觉和听觉信息都存在时，4 个月大的孩子区分 1:3 而不是 1:2 的比例。这些结果表明近似数系统精度在婴儿早期发展，并且可能早在四个月大时就对感觉间冗余敏感。