Complex and often unobservable STEM constructs and processes are represented using a variety of representations, including iconic gestures in which the body is configured or moved to resemble a referent's spatial properties or actions. Earlier researchers have suggested links between gesturing and expertise, leading some to recommend instructional gestures. Earlier research, however, has been largely correlational; furthermore, some gestures may be made with misleading positions or movements. Using the illustrative topic of strike in structural geology, we investigated the existence and impact of inaccurate instructional gestures. In Study 1, we examined videotapes of participants who had been asked to explain strikes to another person. We observed inaccurate (non-horizontal) strike gestures not only among novices (first introduced to strike during the study itself, n = 68) but also among participants who had greater expertise in geology (n = 21). In Study 2, we randomly assigned novices (N = 167) to watch video lessons in which the instructor accompanied verbal explanations of strikes with accurate, inaccurate, or no iconic gestures and tested students' learning on a strike-mapping task. Students with low spatial-perception skills showed no impact of their gestural condition on performance. Students with high spatial-perception skills showed no advantage from accurate gestures but performed significantly worse in the inaccurate-gesture condition. Findings suggest that recommendations to use gestures during instruction should include professional development programs that reduce the occurrence of inaccurate gestures.
Keywords: STEM education; STEM learning; geology instruction; gestures; spatial skills.