When our hands help us understand: Investigations into gesture’s effects on comprehension

It is becoming increasingly clear that gesture benefits learning, but what is less well understood are the reasons why gesture can benefit comprehension, and under which conditions gesture is most beneficial. This thesis aimed to answer questions surrounding when and why gestures benefit comprehension of spoken messages. Across four papers, this thesis investigated 1) potential factors that may moderate gesture’s effects on comprehension of spoken messages in a meta-analysis; 2) whether differential effects of observing gesture on narrative comprehension are found depending on the type of gesture observed, a learner’s age, and task difficulty; 3) whether gesture production by a learner benefits narrative comprehension and/or moderates the effects of observing gesture on narrative comprehension; and 4) whether the observation of gesture benefits narrative comprehension in children with autism spectrum disorder. There were four key findings. First, the meta-analysis presented in Chapter 2 established that gesture benefits comprehension under a variety of circumstances, particularly when gestures are produced as opposed to observed by a learner. Second, Chapter 3 demonstrated that the observation of typical gestures benefited narrative comprehension significantly more than atypical gestures and no gestures, regardless of age or task difficulty. These differential effects of typical and atypical gestures could be partly explained by differences in the semantic relationship between the gestures and accompanying speech, with typical gestures rated as more representative of the narrative events than atypical gestures. Third, as shown through Chapter 4, gesture production did not significantly benefit narrative comprehension, nor did it moderate the effect of observing gesture on narrative comprehension, suggesting gesture production may benefit some tasks more than others. Finally, Chapter 5 established that the observation of gesture significantly benefited narrative comprehension in children with autism spectrum disorder, perhaps in part through capturing attention. This thesis not only showed that gestures have important implications for learning, but also highlighted instances when gestures are beneficial, and in turn, reasons why gestures are beneficial.