Extrinsic context affects perceptual normalization of lexical tone

Area of Science:

• Psycholinguistics
• Auditory Perception
• Phonetics

Background:

• Lexical tone identification is crucial for understanding tonal languages like Cantonese.
• Perceptual normalization, adjusting perception based on context, is vital for consistent interpretation of speech sounds.
• Extrinsic context, such as surrounding speech pitch, plays a role in normalizing auditory perception.

Purpose of the Study:

• To investigate how extrinsic sentential context influences the perceptual normalization of lexical tones in Cantonese.
• To quantify the effect of fundamental frequency (F0) shifts in context on listeners' judgments of a target word's lexical tone.
• To determine the differential impact of preceding versus following context on tonal perception.

Main Methods:

• Four experiments were conducted using semantically neutral Cantonese sentences.
• Listeners heard a target word with a mid-level tone embedded in contexts with manipulated F0.
• Tonal judgments were recorded, and perceptual normalization was measured by the proportion of non-mid-level responses in F0-shifted contexts.

Main Results:

• Listeners' tonal judgments were directly proportional to the degree of F0 shift in the context.
• Perception of lexical tone was not influenced by non-pitch-related talker variations.
• Both preceding and following context affected tonal judgments, with following context having a stronger influence.

Conclusions:

• Perceptual normalization of Cantonese lexical tones appears to utilize a "moving window" or "running average" mechanism.
• This mechanism prioritizes more recent pitch information over older information.
• The process does not rely on the perception of a single voice, indicating robustness to talker variability.