Continuous flash suppression effectiveness depends on mask temporal frequency

A variant of binocular rivalry called Continuous Flash Suppression (CFS) (Tsuchiya & Koch, 2005) has become a popular tool for investigating visual processing outside of conscious awareness (Yang, Brascamp, Kang, & Blake, 2014). In a CFS paradigm, a series of different Mondrian patterns is flashed to one eye at a steady rate, suppressing awareness of the image presented to the other eye (Tsuchiya, Koch, Gilroy, & Blake, 2006). In most studies using CFS the temporal frequency for the mask images is set to 10 (Tsuchiya & Koch, 2005; Tsuchiya et al., 2006) or 20 (Jiang et al., 2009) Hz. To date, little is known about the precise relationship between masking effectiveness and temporal masking frequency. Given the role of temporal factors in many theories of visual awareness, such as phase coupling of neural oscillations across brain regions or re-entrant processing, we investigated the suppression effectiveness of a wide range of masking frequencies (0-32Hz). In a breakthrough CFS paradigm, participants reported whether an image (a face or house) was presented on each trial while Mondrian-like textures were presented as masks. In condition 1, trials with all different frequencies occurred in random order while in condition 2, trials with the same masking frequency were grouped in blocks. 　　We found that the response times differed dramatically between temporal masking frequencies, with mask effectiveness following a log-normal curve peaking around 6Hz in both conditions. The static mask (0 Hz: traditional binocular rivalry) yielded similar breakthrough times as higher frequencies of CFS. In practical terms, these results show that, the 10 Hz/20 Hz frequencies used in most CFS studies may not be optimally effective. More generally, these findings support the idea that temporal factors play a critical role in perceptual awareness. Meeting abstract presented at VSS 2015.