Data and python scripts for plotting figures 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，是支撑语言演化的底层遗传进程。要厘清语言传播的运作机制，我们需要基于语言使用持久性变化的实证证据，构建系统性的机理认知。本研究分析了2亿条在线对话，以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间实现传承，而非仅局限于词汇在个人词库中的二元存在（即是否存在）。我们提出了一种语言传播机制：当个体接触到某一词汇时，存在一定概率会更频繁地使用该词汇。基于该机制，我们测算得出：个体每接触约100个词汇，便会有1个词汇促使其后续更频繁地使用。由于高频词汇被接触的概率更高，这意味着实际被复制传承的是词汇的使用频率本身。除此之外，我们的测算结果显示，这一单次接触式传播机制具备中性特征，无需对对话中遇到的词汇是否为高频词进行额外区分，即可普遍适用。由此衍生出一项重要结论：可通过多个词汇的使用频率协同观测与量化语言传播，本研究结果也验证了这一点。上述结果表明，我们提出的语言传播机制可用于研究群体内的语言模式与演化规律。