Adaptation to motion of a second-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 important in determining the properties of a second-order (contrast) modulation of that carrier. In light of this we examined whether there was any evidence for a motion aftereffect in one-dimensional second-order patterns containing only two sinusoidal luminance components: a spatial beat. The stimuli were either 1 cpd luminance sinusoids or 1 cpd luminance beats modulating a carrier sinusoid of 5 cpd. The magnitude of any motion aftereffect, or any directionally specific effect of adaptation, was measured for all combinations of first and second-order test and adapting patterns. Both flickering and non-flickering stimuli were used. The results indicate that a motion aftereffect is only induced by first-order adapting stimuli, and likewise, is only measurable in first-order test stimuli. We find no evidence for any directionally specific effect of adaptation in second-order stimuli, whether the test is counterphased or otherwise. These results apparently conflict with recent reports of a second-order induced motion aftereffect, but are consistent with many other findings which show differences between the 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 frequency and orientation content of the first-order carrier.
Cropper
S J
SJ
School of Psychology, University of Wales, Cardiff, Wales. simon@chimera.psych.unimelb.edu.au
Hammett
S T
ST
D000221:Adaptation, Ocular / Q000502:physiology*; D015350:Contrast Sensitivity / Q000502:physiology; D005366:Figural Aftereffect / Q000502:physiology*; D006801:Humans; D008027:Light; D009039:Motion Perception / Q000502:physiology*