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Complete adaptation to patterned stimuli: A necessary and sufficient condition for Weber's law for contrast

Incremental (masking) and adaptation contrast thresholds were measured for sinusoidal gratings of different spatial frequencies presented either in an on-off mode or reversed in contrast, at different temporal rates; 2 corrected myopes served as Ss. It was shown that whenever the masking grating stimulated other mechanisms than those concerned with the detection of the test stimulus, the ratio of delta contrast (test)/contrast (mask) was not constant, thereby indicating a departure from Weber's law. It is concluded that Weber's law directly reflects complete adaptation of the stimulated pattern and/or movement mechanism. (17 ref) (PsycINFO Database Record (c) 2005 APA, all rights reserved)



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