Comparison of contrast sensitivity functions across three orientations: implications for theory and testing.
The contrast sensitivity functions of a large group of observers (N = 71) were determined for three orientations of test gratings: vertical, oblique, and horizontal. Comparison of group means indicated that, consistent with previous findings for the 'oblique effect', sensitivity was poorer for the oblique orientation-but only for the mid-high spatial frequencies. Correlation analyses indicated that contrast sensitivity for a particular spatial frequency at a given orientation was highly correlated with contrast sensitivity for that same frequency at the other two orientations. Factor analysis of the intercorrelations revealed two strong factors, a low frequency factor, and a mid-high frequency factor. Results are discussed in terms of: (a) the implications for contrast-sensitivity testing across orientations, (b) the basis for the oblique effect, and (c) a different type of evidence for a dichotomy among spatial-frequency channels that may reflect the distinction between X cells and Y cells or between the parvocellular and magnocellular systems.
Long
G M
GM
Department of Psychology, Villanova University, PA 19085.
Tuck
J P
JP
D000328:Adult; D001288:Attention; D005260:Female; D006801:Humans; D008297:Male; D009949:Orientation; D010364:Pattern Recognition, Visual; D011601:Psychophysics; D011930:Reaction Time; D013028:Space Perception