Dyslexics Don’t Learn From Repetition

Most schoolchildren can hone in on the teacher’s voice even amidst the cacophony of a boisterous classroom. That’s because the typical brain has the automatic ability to focus on auditory information that is repetitious, predictable, and relevant, but it’s different in kids with dyslexia.

The teacher’s voice may become lost within the larger spectrum of background noise, such as chairs scraping across the floor, whispered voices, clanging locker doors, and playground chants. That’s because dyslexic children have trouble separating important auditory information from other, competing sounds.

Sound Regularities

These findings come from research conducted at the Auditory Neuroscience Laboratory at Northwestern University, which offers evidence that kids who have trouble picking out speech from background noise also have a measurable neural (nerve) deficit that has an adverse impact on their ability to take advantage of sound regularities within their sound environments.

Nina Krause, Hugh Knowles Professor of Communication Sciences and Neurobiology and director of the Laboratory, says that in order to hear speech within noise, we must have the ability to single out repetitive elements through a kind of sharpening or fine-tuning of these elements. This is the way we tag voice pitch, a cue that is crucial for singling out a specific voice within an environment of background noise.

Current Context

Krause and her colleagues showed that the brain manages to focus on the relevant factors of the sound environment thanks to an auditory system that is capable of adapting and changing its activity depending upon a current context.

Both typical and poor readers were shown a video as the sound “da” was broadcast in their ears via earphones during two separate sessions. The responses of the subjects’ brains to these sounds were measured.

During the first session, the sound was repeated in a continuous manner. In the second session, the sound “da” was used at random among other verbal sounds. During a third session, behavioral tests were administered to the children. At the same time, the kids were asked to repeat sentences that had been spoken to them against a backdrop of ever-increasing levels of noise.

Repetitive Speech

Even though the typical children were distracted by a movie, their auditory systems were able to tune in to repetitive speech sounds and sharpen the encoding of those sounds. But the poor readers showed no improvement in encoding sounds with repetition. The children with more typical adaptive auditory systems did better on the behavioral tests that required them to try to pick out speech within a busy sound environment.

Beneficial Strategies

The results of this study suggest that poor readers, who have trouble processing auditory information within a noisy background, might benefit from such strategies as situating the student in front of the teacher or using technology to enhance a teacher’s voice for a particular student.