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Electrophysiology and Modelling Highlight Diverse Strategies During Speech Perception

Poster Session B - Sunday, March 8, 2026, 8:00 – 10:00 am PDT, Fairview/Kitsilano Ballroom

Evan Hare¹ (), Weitong Liang⁴, Surya Tokdar^2,4, Tobias Overath^1,2,3; ¹Department of Psychology and Neuroscience, Duke University, ²Duke Institute for Brain Sciences, Duke University, ³Center for Cognitive Neuroscience, Duke University, ⁴Department of Statistical Science, Duke University

Speech signals vary naturally across speakers, contexts, and productions, creating acoustic ambiguity that listeners must resolve to understand spoken language. Research in speech perception proposes that the auditory system handles this variability through probabilistic computation and abstraction, producing categorical perception. Traditionally, this phenomenon is measured by asking participants to label stimuli along a phonetic continuum in a two-alternative forced-choice (2AFC) task, which typically yields a sigmoidal identification curve. However, recent work argues that this pattern may be a product of task structure rather than a reflection of underlying perception. When listeners instead provide continuous judgments, their responses often appear graded, suggesting access to within-category acoustic detail. An alternative explanation is that listeners differ in how they perceive and respond to ambiguous speech, and that these individual strategies shape whether behavior appears categorical or continuous. To evaluate this account, we conducted a two-session experiment combining behavioral and electrophysiological measures. Participants classified 5-step continua spanning /ɪ/–/ɛ/ vowels, /d/–/t/ stop consonants, and /ʃ/–/s/ fricatives in a 2AFC task and rated the same stimuli along a visual analog scale (VAS) in a separate session while EEG recorded neural responses. Behavioral and neural measures were strongly correlated across tasks, indicating consistent individual differences in sensitivity to phonetic ambiguity. Yet more detailed modeling revealed that listeners may flexibly shift perceptual strategies depending on task demands. These findings suggest that categorical and continuous patterns in speech perception reflect both stable individual traits and context-dependent processing strategies.

Topic Area: PERCEPTION & ACTION: Audition