Rarefaction and resolution, stimulus area and detection: an order of priority

The aim of this research was to establish the priority of different effects between phenomenal variables in acuity tasks. The phenomenon we considered--observed at first by Vicario in 1971--is a good example of links between different percepts. In Exp. 1 the threshold of the resolution distance of square gratings having the same phenomenal frequencies (as observed in a 1985 experiment by Vardabasso and Zanuttini), although different areas, was checked. The distance at which the oblique lines, with the same phenomenal frequencies, are distinguished does not differ significantly for the two squares. In Exp. 2 we checked the effect of two different variables--the physical spacing between the lines and the area of the pattern--on detection thresholds on a task which allowed comparing the distance at which a gap in the diagonal of the squared gratings "small and large", "sparse and dense" was detected.