Factors underlying flicker-induced time dilation: Temporal frequency, semantic content, and subjective saliency of...

Flicker-induced time dilation refers to the robust illusion whereby temporally modulated visual stimuli are perceived as lasting longer than static stimuli. Although flicker-induced time dilation has been consistently demonstrated, it remains unclear whether its magnitude is determined solely by low-level temporal dynamics or whether higher-level semantic processing also contributes. The present study investigated the respective roles of flicker frequency, semantic content, and subjective saliency in shaping perceived duration. Using the semantic wavelet-induced frequency tagging image transformation method, we generated semantic (faces and houses) and scrambled flickers presented at 2, 4, and 6 Hz, with and without luminance modulation. In experiment 1, participants performed a duration comparison task to estimate perceived duration. In experiment 2, subjective saliency of the same stimuli was rated. Results showed that increasing flicker frequency reliably enhanced perceived duration. Crucially, semantic content did not modulate perceived duration at any frequency, regardless of luminance modulation. In contrast, subjective saliency increased both with flicker frequency and with semantic information. This dissociation indicates that, although semantic content enhances subjective saliency, it does not contribute to temporal dilation. These findings suggest that distortions in perceived time induced by visual stimuli are primarily shaped by low-level temporal dynamics and increased activity in early visual areas, whereas higher-order visual processing contribute little to the modulation of perceived duration.