ADAPTATION TO MOTION OF A 2ND-ORDER PATTERN - THE MOTION AFTEREFFECT IS NOT A GENERAL RESULT

It has become apparent from recent work that the spatial frequency and orientation content of the first-order (luminance) carrier is very im portant in determining the properties of a second-order (contrast) mod ulation of that carrier, In light of this we examined whether there wa s any evidence for a motion aftereffect in one-dimensional second-orde r patterns containing only two sinusoidal luminance components: a spat ial beat, The stimuli were either 1 cpd luminance sinusoids or 1 cpd l uminance beats modulating a carrier sinusoid of 5 cpd, The magnitude o f any motion aftereffect, or any directionally specific effect of adap tation, was measured for all combinations of first and second-order te st and adapting patterns, Both flickering and non-flickering stimuli w ere used, The results indicate that a motion aftereffect is only induc ed by first-order adapting stimuli, and likewise, is only measurable i n first-order test stimuli, We find no evidence for any directionally specific effect of adaptation in second-order stimuli, whether the tes t is counterphased or otherwise, These results apparently conflict wit h recent reports of a second-order induced motion aftereffect, but are consistent with many other findings which show differences between th e detection of motion for first and second-order stimuli. We conclude that the induction of a motion aftereffect for second-order stimuli is not a general result and is critically dependent upon (amongst other things) the local properties of the stimulus, including the spatial fr equency and orientation content of the first-order carrier. (C) 1997 P ublished by Elsevier Science Ltd.