Gesture as a way to understand what others are thinking

One of the most difficult things for small children to learn is how to take someone else's perspective. If a typical three year old hides a toy when her brother is out of the room, she believes he will know where it is when he returns. By the time they are five, most children will not make this error, and understand that other people have a different perspective on the world than they do. Somewhere around the age of four, children gain the ability to understand that others may believe something to be different from the way they see it themselves. I found an old picture of my kids (who are now no longer nearly as cute) to illustrate this phenomenon:

Another way of saying this is that most three-year-olds have not yet developed a "theory of mind": they don't recognize that others may have "false beliefs." Kids develop an accurate understanding of false beliefs so rapidly around the age of four that psychologists have had a difficult time identifying how this facility is acquired—it's almost as if one day kids don't have it, and the next day they do. Inspired by the work of Susan Goldin-Meadow and her colleagues who found that gestures can aide learning, a team of researchers led by Stephanie Carlson developed a series of experiments to see if kids might understand false beliefs expressed in gesture before they understand false beliefs expressed verbally (Stephanie Carlson, University of Washington; Antionette Wong, Columbia University; and Margaret Lemke and Caron Cosser, University of Washington, "Gesture as a Window on Children's Beginning Understanding of False Belief," Child Development, 2005).

Carlson et al. began by giving 3-, 4-, and 5-year-olds a simple test: they showed them two objects, a crank and a dumbbell, each of which came in its own box, labeled with a picture of the object it contained. They then taught the kids hand gestures to represent each object. The kids quickly learned the gestures and never questioned the fact that the objects did not have verbal names. Then the kids were asked to teach the gestures to an "Ernie" puppet. After Ernie left "to go clean his room," the children were distracted with a game for a few minutes while an experimenter switched the contents of the boxes so that the dumbbell was in the hand-crank box. Then the boxes were returned and the experimenter asked the kids what was in the hand-crank box. They responded with the hand-crank gesture. Then the experimenter, to everyone's apparent surprise, showed the children that the dumbbell was actually in the box. She put it back in the box and Ernie returned. The children were asked what Ernie would think was in the box. Few 3-year-olds, most 4-year-olds, and nearly all 5-year-olds answered correctly. The children were asked to perform a similar verbal task, with nearly identical results. This first experiment seemed to show that there was no difference between verbal expressions of the false-belief test and gestural ones—not exactly what these researchers were expecting.

Undaunted, Carlson and her colleagues reasoned that the mastery of false belief must too rapid to be seen in such a wide age range, and so they developed a more sophisticated test, which they applied to a group of children that were within 6 months of age four. They used two additional objects: a spiky ring and a plastic bee trap, which they invented verbal labels for: kayloo and modee. The new group of kids was asked to perform the identical task for both objects with gestural names (the dumbbell and hand-crank) and verbal names (the "kayloo" and "modee"). Out of the 34 children tested, 18 were found to be at the key transitional phase where they didn't always pass or fail the false belief test. Of these, 11 performed better on the gesture task, and only 4 were better on the verbal task. The researchers had finally found evidence of the mechanism for the elusive transition from inability to understand false belief, to proficiency in this task.

Why might children be more able to accurately understand what someone else is thinking when those thoughts are expressed in gesture? Carlson et al. believe it is because the gesture more closely represents the object: the gesture for the hand-crank, for example, was a cranking motion. It's a simpler mental process to keep this in mind while trying to determine if that's what someone else is thinking, so kids develop the ability to do this task before learning the more complex verbal task.