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BLOOMINGTON, Ind. -- Blind children and sighted children both gesture at the same rates while speaking and use the same range of gesture forms, according to a study by Indiana University psychologist Jana M. Iverson and Susan Goldin-Meadow of the University of Chicago. Further, blind children gesture even when they are aware the listener is blind and unable to receive information conveyed by gesture.
Their results were reported in the Nov. 19 issue of the journal Nature.
"Gesturing is really a window into thought," Iverson said. "The studies of blind speakers provide a nice demonstration of the fact that gesturing and thinking and speaking are tightly interleaved." Gesturing appears to be integral to the speaking process itself and may reflect or even facilitate the thinking that underlies speaking.
One popular theory holds that gesturing is learned behavior. Iverson and Goldin-Meadow decided to test this idea by comparing two groups of 12 children, one in which the children could see and the other in which the children were congenitally blind. The median ages of the blind subjects and sighted speakers were 12 and 11, respectively.
In a study conducted at the University of Chicago, each child was presented with two glasses containing equal amounts of water. The water from one glass was then poured into a shallow but wider dish. The children were asked whether there was the same amount of water in the dish as the glass, and to justify their answers. The blind children were allowed to examine the containers with their hands throughout the experiment.
"It's the kind of task that really gets kids' thinking and reasoning processes going," Iverson explained. "This is a really novel thing for them to do, and they have to be engaged and think hard when they're coming up with an answer."
The study found that all 12 blind speakers gestured as they spoke, despite having never seen a gesture. The blind group gestured at a rate that was not reliably different from that of the sighted group and conveyed the same information using the same range of gesture forms.
"In this task, the kids tended to make a lot of gestures related to the height of the containers," Iverson said. "They would also hold their hands up at different levels indicating the height of the containers, or they would hold hands apart at different distances to indicate that one container was wide and another skinny, or they would gesture as if they were pouring the contents of one container into another."
Another possibility is that speakers may gesture because they understand that gesture can convey useful information to the listener. To test this hypothesis, the researchers ran the same experiment with another group of blind children but used listeners that the participants knew were also blind. They found that blind speakers gestured to blind listeners at a rate not reliably different from the sighted speaker/sighted listener or sighted speaker/blind listener combinations.
"The question I'm pursuing now is what exactly is it that gesturing is doing in the process of thinking and speaking," Iverson said. "I'm currently running a study that looks at what happens when you ask people to not gesture at all, measuring the effects of inhibiting gesture on performance in a memory task. The results should provide a better understanding of what gesturing can tell us about the basic nature of thought."
(Jeff Austin, Office of Communications and Marketing, 812-855-0084, jeaustin@indiana.edu)