The threshold for detecting an equiluminant chromatic spot is approxim
ately halved by the presentation of a coincident, suprathreshold lumin
ance pedestal flash. The dynamics of this facilitation were studied by
varying the duration and temporal asynchrony of the chromatic test fl
ash and luminance pedestal. Facilitation occurs in a narrow temporal w
indow near the chromatic test presentation; masking may occur when the
pedestal is temporally displaced from the test by longer times. The m
echanism producing facilitation lags behind the chromatic signal by at
least 20 msec.