The Goldilocks Zone of Perceptual Learning

Area of Science:

• Psycholinguistics
• Speech Perception
• Auditory Neuroscience

Background:

• Lexically guided perceptual learning (LGPL) updates linguistic categories using lexical context.
• LGPL is crucial for adapting speech perception to novel or variable input.
• The precise range of acoustic variation that supports LGPL remains incompletely understood.

Purpose of the Study:

• To investigate the range of acoustic variation that facilitates lexically guided perceptual learning in speech.
• To determine how different levels of phonetic variation (typical, ambiguous, atypical, remapped) influence LGPL.
• To examine listener sensitivity to acoustic variation in exposure stimuli.

Main Methods:

• Experiment 1: Employed an LGPL paradigm using words with noncanonical /s/ realizations varying along s/ʃ continua (typical, ambiguous, atypical, remapped).
• Speech categorization tasks were used to assess perceptual learning of /s/ and /ʃ/ sounds.
• Experiment 2: Utilized AX discrimination tasks to measure listener sensitivity to variation in the exposure speech tokens.

Main Results:

• Listeners demonstrated significant perceptual learning with maximally ambiguous speech tokens.
• Tokens that elicited the most perceptual learning were not perceptually salient in isolation.
• Listener sensitivity analysis indicated that maximally ambiguous stimuli were not uniquely salient.

Conclusions:

• Perceptual learning in speech is optimized by maximally ambiguous stimuli.
• Highly atypical pronunciations led to reduced perceptual learning, while typical pronunciations showed no learning.
• LGPL involves an interaction between confidence in phonetic/lexical predictions and the typicality of speech categories.