Memory for events may be influenced by other witnesses. If co-witnesses discuss an event, or are exposed to each other's reports of that event, their memories are likely to converge. The present research investigates this 'co-witness influence effect' in young children. Specifically, it examines the developmental mechanisms that regulate the likelihood of being influenced by a co-witness, and separates resultant recall errors based on "social conformity" from those based on "memory failure". In three experiments, children will view a set of slides with a co-witness (either another child or a confederate on a video). Importantly, children will believe that the co-witness is viewing the same set of slides, but these stimuli will in fact differ. At test, the child and the co-witness will answer questions about the slides together and then individually. Children will also complete a battery of theory of mind tasks (false-belief understanding and the appreciation that perceptions and knowledge are causally linked) and a measure of verbal ability. An analysis of the patterns of association between different aspects of theory of mind understanding and errors resulting from exposure to the co-witness' responses will reveal whether theory of mind differentially influences socially and cognitively driven errors in recall.