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. 2004 Feb 25;24(8):1907–1916. doi: 10.1523/JNEUROSCI.4233-03.2004

Figure 3.

Figure 3.

Effect of spatial frequency on perceptual judgments of target speed. A, Structure of the task, which comprised sequential periods for fixation, observation of two gratings, and report of whether the top or bottom grating appeared to move faster. B, Representative psychometric functions for subject 6. Each point plots responses for a single combination of spatial frequency and speed of the test grating and shows the percentage of times the test grating appeared to be faster as a function of the speed of the test grating. Different symbols show data for test targets of different spatial frequencies: ▪, 0.25 cycle/degree; ▵, 0.5 cycle/degree; •, 1 cycle/degree. Curves are the best fits using Equation 1. C, Summary of the effect of spatial frequency on the speed judgments for six subjects. Each symbol plots the speed required for gratings of different spatial frequencies to be judged as moving at the same speed as the 8°/sec, 0.5 cycle/degree test grating. Different symbols show data for different subjects, indicated by the numbers to the side of the different symbols.