Revealing pragmatic processes through a one-word answer: When the French reply Si

•Surveys the way negatively-polarized questions prompt response particles across languages.•Proposes how contrapositive answers can be revealing of pragmatic contributions.•Shows how hallmark pragmatic effects can be extended to conventional expressions.•Includes a remarkable finding in which 4-year-olds are faster than 6-year-olds. Like many languages, European French has a contrapositive response option (Si) to reject the negative content of a question and to express accord with the questioner’s implicit affirmative. Consider the question “Barack does not eat meat?” (in French) where the response Si indicates that he does. Inspired by Gricean analyses, we view Si as an expression that includes a pragmatic component. Based on extant studies on pragmatic inference, we predicted that the Si response ought to appear cognitively costly compared to felicitous Oui and Non answers. We created an original task that enjoins a participant to remove a box’s cover (while searching for a candy) before hearing a puppet’s question. In the critical Negative-Si (NS) condition, the participant finds the candy in, say, a white box (when two boxes are under consideration) and the interlocutor-puppet’s negative question is It is not in the white box? Besides rates of accurate responses, our main dependent variable was Response Reaction Times (RRT’s), viz. the time to naturally voice an answer (Si in this case). Controls were the Affirmative-Oui (AO), Affirmative-Non (AN), and Negative-Non (NN) conditions. Importantly, the puppet began each trial with one of three kinds of prior belief, a) by declaring that the candy is surely in, or; b) surely not in, the to-be-presented box or; c) by saying “I don’t know where it is.” These were included to determine whether answerers consider the questioner’s prior epistemic state when responding. Experiment 1 compared 6-year-olds to adults and found that i) proficient uses of Si are costly with respect to the other three conditions and that; ii) answers in the wake of a “I don’t know where it is” prompt slowdowns when compared to the other two declarations. Both findings are consistent with our pre-registered predictions. Four-year-olds, investigated in Experiment 2, pattern almost identically with the 6-year-olds, with one major exception. Their fastest response occurs when answering Si, leading to a unique developmental effect. Our account for this finding is that four-year-olds rely on a minimally semantic representation of Si, which en