Two experiments investigated gesture as a form of external support for spoken language comprehension. In both experiments, children selected blocks according to a set of videotaped instructions. Across trials, the instructions were given using no gesture, gestures that reinforced speech, and gestures that conflicted with speech. Experiment 1 used spoken messages that were complex for preschool children but not for kindergarten children. Reinforcing gestures facilitated speech comprehension for preschool children but not for kindergarten children, and conflicting gestures hindered comprehension for kindergarten children but nor for preschool children. Experiment 2 tested preschool children with simpler spoken messages. Unlike Experiment 1, preschool children's comprehension was not facilitated by reinforcing gestures. However, children's comprehension also was not hindered by conflicting gestures. Thus, the effects of gesture on speech comprehension depend both on the relation of gesture to speech, and on the complexity of the spoken message.
