Title: How Children and Adults Produce and Perceive Uncertainty in Audiovisual Speech

We describe two experiments on signaling and detecting uncertainty in audiovisual speech by adults and children. In the first study, utterances from adult speakers and child speakers (aged 7-8) were elicited and annotated with a set of six audiovisual features. It was found that when adult speakers are uncertain they are more likely to produce fillers, delays, high intonation, eyebrow movements, and ‘funny faces’. The basic picture for the child speakers is somewhat similar, in that the presence of certain audiovisual cues correlates with uncertainty, but the differences are relatively small and less often significant. In the second study both adult and child judges watched responses from adult and child speakers selected from the first study to find out whether they were able to correctly estimate a speakers’ level of uncertainty. It was found that both child and adult judges give more accurate scores for answers from adult speakers than from child speakers and that child judges overall provide less accurate scores than adult judges.