Influence of stimulus size, spatial envelope, background luminance and shape on flicker detection

Chang-Yeong Han¹, Eun Cho¹, Hyosun Kim², Oh-Sang Kwon¹; ¹Ulsan National Institute of Science Technology, ²Samsung Display Research Center

Temporal Contrast Sensitivity Function (TCSF) increases with stimulus size, which is explained by the higher temporal sensitivity of periphery and probability summation. However, existing studies are largely based on restricted conditions – dark backgrounds and sharp boundary- which could influence the size effect of flicker detection. We supposed that adaptation from dark backgrounds decreases overall sensitivity and sharp boundary enhanced the detection of the flickering edge, particularly at high temporal frequency, driven by unstabilized retinal images at fovea. To test this, we estimated the stimulus size effect on TCSF across varying background luminances (1 vs 98 cd/m2) and spatial envelopes (sharp vs. blurred). The participants responded to the flickering stimulus (98 cd/m2) after watching two sequential intervals. To quantify these effects, we extracted the four properties of TCSF: The peak sensitivity, peak frequency, and the slopes for the low- and high-frequency regions relative to the peak. Results showed that larger stimuli significantly elevated all four properties of the TCSF (p<.01). Importantly, interactions revealed that the size effect on peak frequency was attenuated under dark backgrounds (p < .01), while the size effect on the low-frequency slope was significantly enhanced (p < .05). Additionally, sharp edges amplified the size effect on both peak sensitivity and high-frequency slopes compared to blurred edges (p < .01). Furthermore, we examined the size effect on Critical Flicker Frequency (CFF) by dissociating stimulus area and major-axis length in CFF. While both predicted CFF, stimulus area accounted for a significantly higher proportion of variance (p < .001). We confirmed that the size effect of flicker detection is not merely a product of peripheral sensitivity and probability summation but is also modulated by adaptation levels and spatial contexts from spatial envelope and shape. Our results suggest a need to extend models, providing a foundation for establishing display standards.

Acknowledgements: TCSF, CFF, Stimulus Size, Background Luminance, Spatial Envelope, Shape