When Additional Training Isn't Enough: Further Evidence That Unpredictable Speech Inhibits Adaptation

Area of Science:

• Speech-Language Pathology
• Auditory Perception
• Neurology

Background:

• Familiarization training improves speech intelligibility for individuals with spastic, ataxic, and hypokinetic dysarthria.
• Hyperkinetic dysarthria, characterized by unpredictable speech signal degradations, has not shown intelligibility improvements with standard perceptual training.

Purpose of the Study:

• To investigate if modified perceptual training protocols can improve speech intelligibility for talkers with hyperkinetic dysarthria.
• To test if increased exposure or the addition of vocal imitation feedback enhances perceptual adaptation to unpredictable speech patterns.

Main Methods:

• Experiment 1: Modified exposure levels during perceptual training for hyperkinetic dysarthria.
• Experiment 2: Added vocal imitation (somatosensory feedback) to perceptual training for hyperkinetic dysarthria.

Main Results:

• Neither increased exposure nor vocal imitation feedback improved speech intelligibility for hyperkinetic dysarthria talkers.
• Vocal imitation task significantly reduced listener intelligibility post-training.

Conclusions:

• Perceptual adaptation is inhibited in hyperkinetic dysarthria due to unpredictable speech signal degradations.
• Signal predictability is a crucial factor for theoretical models of perceptual learning in speech.