"I use it when I see it": The role of development and experience in Deaf and hearing children's understanding of iconic gesture.

Iconicity is prevalent in gesture and in sign languages, yet the degree to which children recognize and leverage iconicity for early language learning is unclear. In Experiment 1 of the current study, we presented sign-naïve 3-, 4- and 5-year-olds (n=87) with iconic shape gestures and no additional scaffolding to ask whether children can spontaneously map iconic gestures to their referents. Four- and five-year-olds, but not three-year-olds, recognized the referents of iconic shape gestures above chance. Experiment 2 asked whether preschoolers (n=93) show an advantage in fast-mapping iconic gestures compared to arbitrary ones. We found that iconicity played a significant role in supporting 4- and 5-year-olds' ability to learn new gestures presented in an explicit pedagogical context, and a lesser role in 3-year-olds' learning. Using similar tasks in Experiment 3, we found that Deaf preschoolers (n=41) exposed to American Sign Language showed a similar pattern of recognition and learning but starting at an earlier age, suggesting that learning a language with rich iconicity may lead to earlier use of iconicity. These results suggest that sensitivity to iconicity is shaped by experience, and while not fundamental to the earliest stages of language development, is a useful tool once children unlock these form-meaning relationships.