Gesture is important for language acquisition, but how gesture and its temporal aspects integrate with other informationis not fully known. We manipulated referential ambiguity, and the availability and timing of a deictic gesture duringtraining on a word-learning task with adults to assess how gestural cues alter learning when tested on those words. Wedemonstrate that the presence of a gestural cue during training in a condition with two potential referents can reducereferential ambiguity sufficiently to produce performance at test similar to a condition with only one referent. We furthershow that learners demonstrate better performance at test with gestures that occur prior to, rather than after, the verballabel in training. Gesture during learning thus appears better at predicting, rather than confirming the referent. Theseresults offer insight into how cues can facilitate the disambiguation of meaning during word learning. Pre-registration:https://osf.io/exq7d/?view only=8b28001e56404ff79c2258f3b66d7474 Keywords: word learning; language acquisition;multiple cues; gestures; temporal; word-referent mapping

How infants determine correct word-referent pairings withincomplex environments is not yet fully understood. Thecombination of multiple cues, including gestures, may guidelearning as part of a communicative exchange between parentand child. Gesture use and word learning are interlinked, withearly child gesture predicting later vocabulary size, andparental gesture predicting child gesture. However, the extentto which parents alter gesture cues during word learningaccording to referential uncertainty is not known. In this study,we manipulated the number of potential referents acrossconditions during a word learning task with 18–24-month-olds,and explored how changes in parental gesture use translatedinto infant word learning. We demonstrate that parents altertheir gesture use according to the presence, but not the degree,of referential uncertainty. We further demonstrate that a degreeof variability in the number of potential referents appears tobenefit word learning.

Implicit mentalising involves the automatic awareness others' perspectives. The Joint Simon task demonstrates this as a Joint Simon Effect (JSE): A spatial compatibility effect is elicited more strongly in a Joint Simon versus an Individual go/no-go task. The JSE may stem from spontaneous action co-representation of a social partner's frame-of-reference, which creates a spatial overlap between stimulus-response location in the Joint (but not Individual) task. However, JSE's domain-specificity is debated. We investigated the potential content of co-representation during task-sharing—typical geometric stimuli were replaced with two coloured sets of animal silhouettes. Each set was assigned to either the participant themselves or their partner. Critically, a surprise image recognition task followed, aiming to identify any partner-driven effects in incidental memory exclusive to the Joint task-sharing condition, versus the Individual condition. Bayesian statistics indicated a robust absence of the key JSE, limiting interpretations of incidental memory findings, with implications regarding JSE's replicability.