Humans can communicate even with few existing conventions in common (e.g., when they lack a shared language). We explored what makes this phenomenon possible with a nonlinguistic experimental task requiring participants to coordinate towards a common goal. We observed participants creating new communicative conventions using the most minimal possible signals. These conventions, furthermore, changed trial-by-trial in response to shared environmental and task constraints. Strikingly, as a result, signals of the same form were able to successfully convey contradictory messages from trial to trial. Such behavior implicates what we term "joint inference," in which social interactants are inferring, in the moment, the most sensible communicative convention in light of their common ground. Joint inference may help to elucidate how communicative conventions emerge “instantaneously,” and how they are modified and reshaped into the elaborate systems of conventions involved in human communication, including natural languages
