  The Talbot-Plateau law specifies what combinations of flash frequency,
duration, and intensity will yield a flicker-fused stimulus that matches the
brightness of a steady stimulus. It has proven to be remarkably robust in its
predictions, and here we provide addition support though the use of a contrast
discrimination task. However, we also find that the visual system can register
contrast when the combination of frequency and duration is relatively low.
Flicker-fused letters are recognized even though they have the same physical
luminance as background. We propose that this anomalous result is produced by
large disparities in the duration of bright and dark components of the flash
cycle, which brings about unexpected differential activation of ON and OFF
retinal channels.
