Phylogenetic comparison of manual action between humans and apes

婴儿语言能力发展过程中一个值得注意的事件是牙牙学语的开始。虽然咿呀学语的发展在“规范音节产生”中达到高潮，但前一阶段的特征是“边缘咿呀学语”，其具有良好的边缘（辅音）和核心（元音），但包括缓慢（超过120 ms）的共振峰过渡。在这个边缘的牙牙学语阶段，婴儿经常进行特定的手动动作模式，有节奏的敲打，与牙学语的产生同步。这种同步帮助婴儿产生那些具有快速共振峰转换的声音，一旦婴儿获得了产生规范牙牙学语的运动技能，这些声音就会减少。失聪婴儿也会发出边缘性的牙牙学语。然而，边缘咿呀学语阶段从未过渡到典型咿呀学语阶段。此外，这种同步起源于婴儿4个月大时，并且首先表现为笑声和刻板的腿部运动之间的同步，通过这种同步促进了多音节声音的产生。

A notable event that occurs in the development of the infant's speech capabilities is the onset of babbling. Although the development of babbling culminates in "canonical syllable production", preceding stage is characterized by "marginal babbling", which has a well-formed margin (consonant) and nucleus (vowel) but includes a slow (more than 120 ms) formant transition. During this marginal babbling stage, specific pattern of manual action, rhythmic banging, is frequently performed by the infant, synchronizing with the babbling production. This synchronization helps the infant produce those sounds that with rapid formant transition, and once the infant acquires the motor skills to produce canonical babbling, diminishes. Deaf infants also utter marginal babbling. However marginal babbling stage never transits to canonical babbling stage. Furthermore such synchronization originates when the infant is still 4 month old, and appears first as synchronization between laughter and stereotypic leg movement, by which multi-syllabic sound production is facilitated.