A perceptual grouping model for auditory kappa effects

Current models suggest that perceptual time dilation between sequential auditory events with greater pitch separation, known as "auditory kappa effects," arises from auditory motion percepts. The prevailing explanation attributes this effect to violations of expected pitch trajectories, as the perceptual system imputes a constant pitch velocity across events. We tested this auditory motion hypothesis against an alternative auditory grouping hypothesis, which proposes that pitch-timing interactions promote the grouping or segregation of auditory events, leading to subjectively shorter or longer perceived intervals between tones. We conducted two experiments to compare kappa effects across sequences with varying pitch separations (velocities) and sequences with inconsistent pitch trajectories, which precluded stable pitch-velocity references. Experiment 1 results showed larger kappa effects for sequences with slower pitch velocities, contradicting the motion hypothesis, and Experiment 2 showed robust kappa effects based on pitch proximity, regardless of unpredictable pitch motion. Phenomenological models associated with each hypothesis demonstrated that the auditory grouping model provided a better fit to our behavioral data in Experiment 2. These findings support perceptual grouping and segregation as fundamental processes underlying timing judgments and challenge our current understanding of feature interactions in auditory perception. (PsycInfo Database Record (c) 2026 APA, all rights reserved).