Andrew Lisech¹ (), Jaeseon Song¹, Josiane Mukahirwa¹, Keith A. Schneider¹; ¹University of Delaware

Introduction: The mechanisms governing central temporal limits in the brain remain poorly understood. Previous research suggests that our capacity to perceive high-frequency temporal flicker stimuli exceeds our ability to discern changes in their temporal properties. Here we investigated whether a central bottleneck constrains temporal phase discrimination across the visual and auditory systems. Methods: In separate visual and auditory experiments, fifteen participants judged whether sinusoidally oscillating stimulus pairs were in-phase or 180° counter-phase. In the visual experiment, dichoptically presented Gaussians were compared as they oscillated between light and dark states. In the auditory experiment, participants judged the phase of amplitude-modulated dichotic tone sequences. Using the method of constant stimuli, phase discrimination thresholds were measured across nine randomly-interleaved amplitude frequencies (1–30 Hz), with 25 repetitions per frequency. Accuracy data were fit to a cumulative normal function to derive 75% accuracy thresholds for each participant. Interstimulus distances were increased to minimize interference from low-level motion detection and other peripheral processes. Results: The study’s main finding revealed that both visual and auditory systems exhibited phase discrimination limits between 7–12 Hz, indicating similar temporal constraints across modalities. Conclusion: Comparable frequency thresholds in vision and audition lend support to the hypothesis of a central processing bottleneck for temporal phase discrimination, rather than independent modality-specific limitations. These shared limitations may reflect the temporal properties of a unified temporal mechanism governing phase perception. To further investigate central temporal limits and their related mechanisms, future research should examine how this bottleneck operates in audiovisual integration and other multisensory contexts.