The study’s authors suggest that this discrepancy may emerge fromdifferences in boys’ and girls’ experience: boys are more likely to play withspatially oriented toys and video games, they note, and may become morecomfortable making spatial gestures as a result. Another study, this oneconducted with four-year-olds, reported that children who were encouraged togesture got better at rotating mental objects, another task that draws heavily onspatial-thinking skills. Girls in this experiment were especially likely to benefitfrom being prompted to gesture.

Yet the most popular and widely viewed instructional videos available onlinelargely fail to leverage the power of gesture, according to a team ofpsychologists from UCLA and California State University, Los Angeles. Theresearchers examined the top one hundred videos on YouTube devoted toexplaining the concept of standard deviation, an important topic in the study ofstatistics. In 68 percent of these recordings, they report, the instructor’s handswere not even visible. In the remaining videos, instructors mostly used theirhands to point or to make emphatic “beat” gestures. They employed symbolicgestures—the type of gesture that is especially helpful in conveying abstractconcepts—in fewer than 10 percent of the videos reviewed.

“symbolic gestures”—movementsthat capture the overall meaning of the speaker’s message—along with what arecalled “beat gestures”: hand motions that serve to punctuate a particular point.