Echo phonology was originally proposed to account for obligatory coordination of manual and mouth articulations observed in several sign languages. However, previous research into the phenomenon lacks clear criteria for which components of movement can or must be copied when the articulators are so different. Nor is there discussion of which nonmanual articulators can echo manual movement. Given the prosodic properties of echoes (coordination of onset/offset and of dynamics such as speed) as well as general motoric coordination of various articulators in the human body, we expect that the mouth is not the only nonmanual articulator involved in echo phonology. In this study, we look at a fixed set of lexical items across 36 sign languages and establish that the head can echo manual movement with respect to timing and to the axis/axes of manual movement. We propose that what matters in echo phonology is the visual percept of temporally coordinated movement that repeats a salient movement property in such a way as to give the visual impression of a copy. Our findings suggest that echoes are not obligatory motor couplings of two or more articulators but may enhance phonological distinctions that are otherwise difficult to see.

中文翻译：

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扩展回声：协调头部发音作为手语音韵学中的非手动增强

回声音位学最初被提议用于解释在几种手语中观察到的手动和嘴巴发音的强制性协调。然而，之前对这种现象的研究缺乏明确的标准，当咬合架如此不同时，哪些运动组件可以或必须被复制。也没有讨论哪些非手动咬合架可以响应手动运动。考虑到回声的韵律特性（起始/偏移的协调和速度等动力学的协调）以及人体中各种咬合器的一般运动协调，我们预计嘴不是唯一参与回声语音学的非手动咬合器。在这项研究中，我们研究了 36 种手语中的一组固定词汇项，并确定头部可以根据时间和手动运动的轴/轴来响应手动运动。我们提出，在回声音韵学中，重要的是时间协调运动的视觉感知，它以这种方式重复显着的运动属性，从而产生副本的视觉印象。我们的研究结果表明，回声不是两个或多个咬合架的强制性运动耦合，但可能会增强难以看到的语音差异。