You have probably heard this advice: stand still, keep your hands at your sides, and do not distract the audience with unnecessary movement.
It sounds professional. It sounds controlled. In this experiment, it made a demanding explanation harder.
Adults and children remembered more information when they were allowed to gesture while explaining a math problem. Gesture was not only for the audience. It helped free the speaker's working memory.
Here, “smarter” means having more working memory available during a demanding explanation. The people who gestured remembered more of the separate memory task. The study did not test what an audience remembered.
What the researchers tested
The final analysis included 26 children and 32 adults who gestured when allowed.
The children solved addition problems. The adults solved factoring problems. After each problem, participants received unrelated information to remember: words for children and letters for adults.
They then explained their solution under two conditions. In one, they could move their hands naturally. In the other, they had to keep their hands still on a table. After the explanation, they recalled the words or letters.
Both groups recalled a significantly larger proportion of items when they gestured. The benefit was clearest for the longer, more demanding memory lists.
The researchers also examined participants who sometimes chose not to gesture even when movement was allowed. Those participants also remembered more on difficult lists when they gestured. This reduced the chance that the instruction to keep still was the only source of the effect.
What the study did not test
The memory task measured the speaker's working memory. It did not measure what an audience remembered from the explanation.
It also used mathematical explanations with spatial content. The authors note that gesture may be especially helpful for spatial information. We cannot assume the same effect size for every type of speech.
Finally, the study does not support choreographing constant movement. Natural gestures that represent an idea are different from repetitive movements with no connection to the message.
Why gesture may help
Speech and gesture can represent information in different forms. A hand movement can carry spatial or relational information while the verbal system handles the words.
The authors suggest that this division reduces the load on verbal working memory. Cognitive capacity remains available for the unrelated memory task.
The exact mechanism was not settled by the experiment. The important result is behavioral: participants remembered more when they gestured.
What speakers can do
Rehearse in the posture you will use
If you will stand during the presentation, practice standing. Give your hands room to move. Sitting motionless at a desk creates a different physical task.
Let useful gestures happen
Do not suppress a gesture that naturally shows size, direction, sequence, or contrast. It may help you organize the explanation as well as helping the audience see the relationship.
Remove repetitive movement, not all movement
A repeated flap, clasp, or point can distract. Review the pattern and replace it with stillness between purposeful gestures.
Keep the claim narrow
Gesture is one tool for managing a complex explanation. It does not replace a clear point, a logical sequence, or good evidence.
The bottom line
Gesturing did not consume the speakers' limited memory capacity in this experiment. It freed some of it.
That makes “keep your hands still” more than dated advice. For a demanding explanation, it can remove a tool your mind was already using. Move when the movement serves the thought. Be still when stillness serves it better.
You can use impromptu speaking practice while standing, then review the recording for clarity and structure.