Quantifying the Influence of Lexical Surprisal on Acoustic Speech Encoding While Controlling for Within-Speaker...

Area of Science:

• Cognitive Neuroscience
• Auditory Perception
• Speech Processing

Background:

• The listening brain predicts upcoming speech, integrating predictions with sensory input.
• Top-down information may influence acoustic speech processing based on semantic context.
• Speaker enunciation variations can confound the study of listener predictions.

Purpose of the Study:

• To investigate the influence of word predictability (surprisal) on acoustic speech processing.
• To control for speaker dynamics when assessing top-down prediction effects.
• To determine if predictability impacts acoustic encoding independently of enunciation.

Main Methods:

• Analyzed electroencephalography (EEG) data from 14 adults.
• Used a perceptual pop-out task with degraded speech enhanced by prior information.
• Controlled acoustic information while varying word predictability and speaker dynamics.

Main Results:

• Behavioral results confirmed the effectiveness of the predictability manipulation.
• EEG indices of word surprisal processing mirrored behavioral findings.
• A relationship between word surprisal and EEG tracking of acoustics emerged for intelligible degraded speech, but not unintelligible speech.

Conclusions:

• Top-down word predictability influences acoustic encoding of natural speech.
• This influence is independent of variations in speaker enunciation.
• Predictability enhances speech comprehension by modulating early auditory processing.