Four subjects were repeatedly presented with all possible pairs of nine gray patches presented under a constant illumination of 133.27 cd/m^2. Stimuli had a size of 0.81 degrees of visual angle and were presented side by side with a distance of 2.32 degrees of visual angle.
On each trial, subjects judged whether the two patches looked same or different.
A data frame of seven variables and 35,760 observations:
the response of a subject in each trial, either
for same or
d for different.
reaction time from stimulus onset until reaction of subject.
number of experimental session.
stimulus which was presented in the first observation area; in this case: on the left side of the monitor.
stimulus which was presented in the second observation area.
which mouse button was pressed. Assigment of same and different to the mouse buttons varied between subjects.
Umbach, N (2013). Dimensionality of the Perceptual Space of Achromatic Surface Colors. Dissertation, University of Tuebingen.