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 frequency of word usage is inherited over conversations, not just the binary presence or the 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 someone 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）指词汇等语言特征在人际间的传递过程，是支撑语言演化的传承机制。为厘清语言传播的运作逻辑，我们需要基于语言使用持久变化的实证证据，构建系统性的机理认知。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，对话中传递的不仅是个体词库中词汇的存在与否二元状态，词汇的使用频率本身也会得到传承。据此我们提出一种语言传播机理：当个体接触到某一词汇时，存在一定概率会更频繁地使用该词汇。基于该机理，我们测算得出：个体每接触约100个不同词汇，便会有1个词汇促使其后续更频繁地使用该词。由于高频词汇的接触频次更高，这意味着实际被传递的正是词汇的使用频率。此外，我们的测算结果表明，这一单次接触传播机理具有中性特征：无论对话中接触的词汇是否为高频常用词，该机理均无差别地适用。由此衍生的一项重要结论是，可通过多个词汇的使用频率协同观测与量化语言传播，我们的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理可用于研究群体内的语言模式与演化规律。