The orientation specificity of two visual after-effects

1. Inspection of a high-contrast adapting grating produces two visual after-effects: ( a ) the contrast threshold is raised for test gratings of similar spatial frequency to that of the adapting pattern and ( b ) the apparent spatial frequency of test gratings shifts away from that of the adapting grating—higher frequencies seem higher and lower ones lower than they really are. 2. Both after-effects are orientation-specific. A horizontal adapting grating influences neither the threshold nor the apparent spatial frequency of vertical test gratings. 3. The magnitude of the two after-effects was measured with vertical test gratings as a function of ( a ) tilt of a high-contrast adapting grating and ( b ) contrast of a vertical adapting grating. 4. At all frequencies of the test grating, the decline of both after-effects produced by an increase in tilt of approximately 6¾° could be matched by a reduction in contrast by a factor of 2. 5. We take this as evidence for a common neural origin for these two visual phenomena.