Learning to talk also changes the way speech sounds are heard, according to a new study published in Proceedings of the National Academy of Sciences by scientists at Haskins Laboratories, a Yale-affiliated research laboratory. The findings could have a major impact on improving speech disorders.
"We've found that learning is a two-way street; motor function affects sensory processing and vice-versa," said David J. Ostry, a senior scientist at Haskins Laboratories and professor of psychology at McGill University. "Our results suggest that learning to talk makes it easier to understand the speech of others."
As a child learns to talk, or an adult learns a new language, Ostry explained, a growing mastery of oral fluency is matched by an increase in the ability to distinguish different speech sounds. While these abilities may develop in isolation, it is possible that learning to talk also changes the way we hear speech sounds.
Ostry and co-author Sazzad M. Nasir tested the notion that speech motor learning alters auditory perceptual processing by evaluating how speakers hear speech sounds following motor learning. They simulated speech learning by using a robotic device, which introduced a subtle change in the movement path of the jaw during speech.
To assess speech perception, the participants listened to words one at a time that were taken from a computer-produced continuum between the words "had" and "head." In the speech learning phase of the study, the robot caused the jaw to move in a slightly unusual fashion. The learning is measured by assessing the extent to which participants correct for the unusual movement.