Word sample used in the manuscript from How humans transmit language: horizontal transmission matches word frequencies among peers on Twitter.

Language transmission, the passing on of language features such as words between people, is the process of inheritance that underlies linguistic evolution. To understand how language transmission works, we need a mechanistic understanding based on empirical evidence of lasting change of language usage. Here, we analysed 200 million online conversations to investigate transmission between individuals. We find that the frequency of word usage is inherited over conversations, rather than only the binary presence or absence of a word in a person's lexicon. We propose a mechanism for transmission whereby for each word someone encounters there is a chance they will use it more often. Using this mechanism, we measure that, for one word in around every hundred a person encounters, they will use that word more frequently. As more commonly used words are encountered more often, this means that it is the frequencies of words which are copied. Beyond this, our measurements indicate that this per-encounter mechanism is neutral and applies without any further distinction as to whether a word encountered in a conversation is commonly used or not. An important consequence of this is that frequencies of many words can be used in concert to observe and measure language transmission, and our results confirm this. These results indicate that our mechanism for transmission can be used to study language patterns and evolution within populations.

语言传播（Language transmission）指人与人之间传递词汇等语言特征的过程，是为语言演化奠定基础的遗传传递过程。为明晰语言传播的运作逻辑，我们需要基于语言使用持续性变化的实证证据，构建其机理层面的认知。本研究通过分析2亿条在线对话数据，探究个体间的语言传播行为。研究发现，词汇使用频率会在对话交互中实现传递，而非仅局限于个体词库中词汇的二元存在状态（即个体是否掌握该词汇）。我们提出一种语言传播机理：当个体接触到某一词汇时，存在一定概率会提升该词汇的自身使用频率。基于该机理，我们测算得出：个体每接触约100个词汇，便有1个词汇会使其后续使用频率有所提升。由于高频常用词汇的接触频次本就更高，这意味着实际被传递的正是词汇的使用频率本身。除此以外，测算结果显示，该基于单次接触的传播机理具有中立性：无论对话中接触的词汇是否为高频常用词，该机理均同等适用，无需额外区分。该结论的一项重要应用价值在于，可通过联合分析多个词汇的使用频率，观测并量化语言传播过程，本研究结果也验证了这一论断。上述结果表明，本研究提出的语言传播机理可用于探究群体内部的语言模式与演化规律。