Apparent fineness of stationary compound gratings

Patterns consisting of the sum of a sinusoidal grating and its second spati al harmonic have an apparent spatial fineness, or periodicity, that is abou t halfway between the two component spatial frequencies. There are also pha se dependent modulations of the apparent fineness about the mean fineness s hift. Covariance between individuals' phase dependent fineness shifts indic ates the presence of four spatial phase channels. The apparent fineness eff ects, and the putative phase channels, may both be a product of a local, li near, analysis of spatial frequency content. Illusory second harmonics, as generated in the spatial frequency doubling illusion, also change apparent fineness. (C) 1999 Elsevier Science Ltd. All rights reserved.