Sustained and transient temporal integration functions depend on spatial frequency, not grating area.

Contrast sensitivity for sinusoidal gratings was measured by a two-alternative forced-choice method and plotted as a function of duration. Gratings of large or small area and low or high spatial frequency (0.75 or 8.25 c/deg) were used. The temporal integration curve was much flatter in the low spatial frequency conditions than in the high frequency conditions, but its shape did not depend on the area of the grating. The results support the established view that the visual system exhibits transient temporal properties at low spatial frequencies and sustained properties at higher frequencies, but disconfirm the recent proposal that temporal integration depends on the area of the grating (expressed in square-cycles) rather than its spatial frequency.