Gesture as a mechanism of change in the interface between spatial language and cognitive development

Children often use gestures to express concepts before expressing them in speech, particularly in domains rich in visual-spatial information. For example, spatial relations such as left-right are cognitively and linguistically challenging for children. Consequently, 8-year-olds struggle to convey these complex relations verbally, but they frequently rely on gestures to describe these spatial concepts informatively. This study builds on this prior work on the descriptions of left-right relations to investigate further (1) the differing functions of gestures (complementary or redundant) in relation to speech in both children and adults; (2) the change in semantic information conveyed in both of these types of gestures in childhood to adulthood, aiming to shed light on the interaction between spatial language and spatial cognitive development. Eight-year-old and adult monolingual Turkish speakers described pictures of objects in left-right spatial relations shown among a quartet of other types of spatial relations between these objects. Results demonstrated that when describing left-right relations between objects, children, compared to adults, provided more under-informative descriptions (i.e., using “side” instead of “left-right”) in speech but used complementary gestures to convey missing information multimodally. Adults already used informative spatial terms in speech and used gestures mostly redundantly. Moreover, children showed a preference for iconic gestures depicting the relative locations of objects over directional pointing gestures indicating single locations, especially when gestures complemented speech. In contrast, adults showed no reliable preference for either gesture type. These results indicate the significance of gestures as mechanisms of change, alongside speech, in spatial language and cognition, particularly in the context of describing cognitively complex left-right spatial relations between objects. • Children use complementary gestures to convey left–right spatial information that is under-specified in speech. • Adults rely primarily on informative spatial language, with gestures serving a mostly redundant role. • Development from childhood to adulthood involves a shift in both gesture function and semantic content in left–right descriptions.