The power and precision with which humans link language to cognition is unique to our species. By 3–4 months of age, infants have already established this link: simply listening to human language facilitates infants’ success in fundamental cognitive processes. Initially, this link to cognition is also engaged by a broader set of acoustic stimuli, including non-human primate vocalizations (but not other sounds, like backwards speech). But by 6 months, non-human primate vocalizations no longer confer this cognitive advantage that persists for speech. What remains unknown is the mechanism by which these sounds influence infant cognition, and how this initially broader set of privileged sounds narrows to only human speech between 4 and 6 months. Here, we recorded 4- and 6-month-olds’ EEG responses to acoustic stimuli whose behavioral effects on infant object categorization have been previously established: infant-directed speech, backwards speech, and non-human primate vocalizations. We document that by 6 months, infants’ 4–9 Hz neural activity is modulated in response to infant-directed speech and non-human primate vocalizations (the two stimuli that initially support categorization), but that 4–9 Hz neural activity is not modulated at either age by backward speech (an acoustic stimulus that doesn't support categorization at either age). These results advance the prior behavioral evidence to suggest that by 6 months, speech and non-human primate vocalizations elicit distinct changes in infants’ cognitive state, influencing performance on foundational cognitive tasks such as object categorization.

中文翻译：

---

听觉诱发的神经活动的发育变化是婴儿语言和认知之间联系的基础

人类将语言与认知联系起来的力量和精确度对于我们这个物种来说是独一无二的。到 3-4 个月大时，婴儿已经建立了这种联系：简单地听人类语言有助于婴儿在基本认知过程中取得成功。最初，这种与认知的联系也受到更广泛的声学刺激的影响，包括非人类灵长类动物的发声（但不包括其他声音，如倒向语音）。但到了 6 个月时，非人类灵长类动物的发声不再赋予这种语言持续存在的认知优势。仍然未知的是这些声音影响婴儿认知的机制，以及最初范围更广的特权声音是如何在 4 到 6 个月之间缩小到只有人类语言的。这里，我们记录了 4 个月大和 6 个月大的婴儿对声学刺激的脑电图反应，其对婴儿对象分类的行为影响已被确定：婴儿定向语音、反向语音和非人类灵长类动物的发声。我们记录到，到 6 个月大时，婴儿的 4-9 Hz 神经活动会因婴儿定向语音和非人类灵长类动物发声（最初支持分类的两种刺激）而受到调节，但 4-9 Hz 神经活动不是在任一年龄被后向语音调制（在任一年龄都不支持分类的声学刺激）。这些结果推进了先前的行为证据表明，到 6 个月时，言语和非人类灵长类动物的发声会引起婴儿认知状态的明显变化，