[P2] Poster: Day 2

[P2-02] Does Semantic Modulation Induce Time Dilation? The Role of Flicker Frequency and Visual Saliency

*Takeya Oda¹, Amirmahmoud Houshmand Chatroudi², Yuko Yotsumoto¹ (1. The University of Tokyo (Japan), 2. Sony Computer Science Laboratories (Japan))

Keywords:

time dilation,semantic flicker,SWIFT,saliency

Flicker-Induced Time Dilation (FITD) describes the phenomenon where the perceived duration of a stimulus is overestimated due to its flickering nature. Recent findings suggest that semantic content might also play a role in modulating perceived time. This study aimed to explore the contribution of ventral visual pathway activation to FITD. To this end, we utilized a variety of flickering stimuli whose frequencies were systematically modulated. Alongside scrutinizing the impact of semantic information, flicker frequency was parametrically manipulated to examine the interplay between stimulus saliency and the perception of time. The Semantic Wavelet-Induced Frequency Tagging (SWIFT) technique was employed to generate scrambled and semantic flicker stimuli. A critical aspect of these stimuli was the preservation of low-level visual characteristics across all frames for both flicker types. In the first experiment, standard stimuli comprised scrambled and semantic flickers presented at 2, 4, and 6 Hz. While both categories of flickers were designed to evoke minimal responses in early visual processing areas, the semantic variants were specifically intended to preferentially engage higher-level regions within the ventral visual pathway. The second experiment introduced luminance-based flickers (scramble/semantic) at identical frequencies to ensure robust activation of low-level visual regions. A consistent and strong influence of flicker frequency on perceived duration was evident across both experimental setups, a conclusion supported by inclusion Bayes factors of BF_incl = 14.04 in Experiment I and > 1000 in Experiment II, indicating strong to extreme evidence. In contrast, the type of stimulus (scramble/semantic) provided only anecdotal support for any discernible effect. These observations imply that higher rates of flicker reliably result in a greater degree of time dilation, whereas the semantic nature of the stimuli appears to have a minimal effect. The observed increase in time dilation as a function of frequency was notably amplified when early visual cortices were more intensely engaged. Future investigations will focus on elucidating the connection between subjective saliency and time dilation by behaviorally assessing the perceived salience of each type of flicker stimulus.