Variations in unisensory speech perception explain interindividual differences in McGurk illusion susceptibility

Area of Science:

• Speech perception
• Audiovisual integration
• Cognitive psychology

Background:

• Face-to-face communication integrates auditory speech with visual facial movements.
• The McGurk illusion is a key tool for assessing audiovisual integration, revealing perceptual confounds.
• Bayesian causal inference theories propose how auditory and visual speech signals are combined.

Purpose of the Study:

• To investigate how unisensory categorical perception of auditory and visual speech affects McGurk illusion susceptibility.
• To determine if McGurk illusion rates vary with individual differences in unisensory speech perception.
• To assess the stability of McGurk illusion susceptibility across different sessions and tasks.

Main Methods:

• Three experiments were conducted to measure McGurk illusion rates.
• Participants' categorical perception of unisensory auditory and visual speech stimuli was assessed.
• The stability of illusion susceptibility was tested across different days and tasks.

Main Results:

• Unisensory categorical perception of auditory and visual speech strongly predicted McGurk illusion rates across participants and speakers.
• Variability in McGurk illusion susceptibility was explained by variations in unisensory categorical perception.
• The stability of McGurk illusion susceptibility correlated with the stability of unisensory categorical perception.

Conclusions:

• Unisensory speech perception performance is a crucial factor influencing audiovisual integration and McGurk illusion susceptibility.
• Individual differences in how people perceive unisensory speech sounds significantly impact their susceptibility to audiovisual illusions.
• Accounting for variations in unisensory perception and stimulus materials is essential when using audiovisual illusions to study integration capabilities.