Susan Wagner Cook stands at the front of a third-grade classroom, an unfinished equation printed neatly on the whiteboard.
4 + 3 + 6 = __ + 6
“I want to make one side,” she says, as her left hand sweeps under the left side of the equation, “equal to the other side,” she continues, now sweeping her right hand under the right side of the equation.
It’s a concept that third-graders are just ready to learn: The total value on one side of an equal sign should equal that on the other.
Some kids get it quickly as Cook goes through her carefully choreographed tutorial. Others take longer. But what none of them know is that they are subjects in an experiment that is helping scientists understand one of the most familiar and yet mysterious components of human behavior: the hand gesture.