Description Usage Format Source References Examples

A pair of adjacent, horizontal luminance gratings (sine- or square-wave spatial profiles, 0.8 cycles/degree and equal contrast = 0.30) drifting at 2 or 8 Hz. The gratings were separated by a 30-arcmin lateral gap. On each trial, the grating pair was drifting either upward or downward and the phase shift between the gratings was chosen at one of 8 values between -50 and 50 degrees. The observer was instructed to report which grating appeared shifted upward. The method of constant stimuli was used.

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A data frame with 64 observations on the following 8 variables.

`Phaseshift`

a numeric vector giving the Phaseshift between the pair of gratings

`WaveForm`

a factor with levels

`Sine`

`Square`

giving the spatial luminance profile of the gratings`TempFreq`

a factor with levels

`2`

`8`

indicating the temporal frequency in Hertz of the moving gratings`Pc`

a numeric vector, indicating the proportion of trials on which a particular grating appeared to be shifted upward

`Direction`

a factor with levels

`Downward`

`Upward`

indicating the direction of motion of the grating pair.`N`

a numeric vector indicating the number of trials on which a condition was presented

`NumUpward`

a numeric vector indicating the number of trials on which the observer responded that a particular grating was shifted upward

`NumDownward`

a numeric vector indicating the number of trials on which the observer reported a particular grating as shifted downward

Data kindly provided by H. Sun.

H. Sun, B. B. Lee and R. C. Baraas Systematic misestimation in a vernier task arising from contrast mismatch, *Visual Neuroscience*, 2008, 25, 365–370.

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