From "um" to "yeah": Producing, predicting, and regulating information flow in human conversation

Speakers must call words to mind, listeners must make sense of them, and both together must negotiate this flow of information, all in fractions of a second. We used large language models to study how this works in a large-scale dataset of English-language conversation, the CANDOR corpus. We provide a new estimate of the information density of unstructured conversation, of approximately 13 bits/second, and find significant effects associated with the cognitive load of both retrieving, and presenting, that information. We also reveal a role for backchannels-- the brief yeahs, uh-huhs, and mhmms that listeners provide--in regulating the production of novelty: the lead-up to a backchannel is associated with declining information rate, while speech downstream rebounds to previous rates. Our results provide new insights into long-standing theories of how we respond to fluctuating demands on cognitive resources, and how we negotiate those demands in partnership with others. Keywords: Conversation may be the "mark and cause of friendship" [1] with a deep evolutionary history [2, 3], but it is also cognitively demanding. Speakers must translate thought into speech [4], while listeners, in turn, face a nowor-never bottleneck in making sense of what they hear before it vanishes from mind [5]. The mental workload includes not just language processing [6], but the theory of mind required to sustain mutual understanding [7, 8, 9, 10].