The correlation principle in human vision

The detection of compound sinusoidal gratings of various spatial frequency separations and four different grating sizes has been studied using the summation to threshold paradigm (Kulikowski and King Smith 1973; Watson 1982). Contrast interrelation functions have been measured and spatial frequency tuning estimates, based on the slope of the contrast interrelation function at two definite points, were derived using the ''negative gradient technique'' proposed by Logvinenko (1995). It is shown that compound grating detection can be modeled by assuming pattern specific sensory mechanisms for each of the spatial frequency components, which adapt to periodicity and size of the stimulus but not to its envelope function. Further, it is shown that relative sensitivity for a given spatial frequency separation can be predicted by the correlation of the grating components used for superposition with good accuracy. As most plausible implementation of the pattern correlation principle in human grating detection the "grating cell" model (von der Heydt et al. 1992) is suggested.