Chromatic flicker perception in human peripheral vision under mental load

Results from two experiments testing flicker sensitivity are presented. Human sensitivity at different visual angles (35, 60 and 90), base-color points (red, green and blue), color attributes (Lightness, Chroma and hue) and frequencies (5Hz, 10Hz, 20Hz, 40Hz and 60Hz) were determined using a detection task and fitting of a psychometric curve. Results demonstrate a large effect of eccentricity on the flicker perception. For chroma and hue flicker the sensitivity decreases with the increasing eccentricity at all frequencies. The results for lightness changes show a more complex frequency dependance, with higher sensitivity at larger visual angles for frequencies lower than 15Hz. Generally, we have higher sensitivity to lightness flicker as compared to Chroma and hue flicker for all eccentricities and all frequencies. Lightness, contrary to chroma and hue, is also independent of the base color point. The second experiment demonstrated that mental load significantly impairs detection of flicker in the periphery. The color model used to create the stimuli was designed for central vision and does not account for the density of cones and rods in the, far periphery and their interactions. This explains the visibility of chromatic changes even at 90 degrees. Still, for some base points and directions of change, no flicker was detected at any frequency and amplitude for the largest visual angle.