Difference test sensitivity: Cognitive contrast effects

Judges performed 3-AFC tests between "threshold" concentrations of NaCl solutions and purified water stimuli. For some 3-AFCs, NaCl was the odd stimulus (S-odd); in others, water was the odd stimulus (W-odd). In one condition, interstimulus rinses were different from the stimuli; in a second condition they were the same. The 3-AFCs in which the interstimulus rinses were different from the stimuli yielded a higher d'. When interstimulus rinses were the same as the stimuli, S-odd 3-AFCs had a higher d' than W-odd 3-AFCs. The same was not true when the interstimulus rinses were different from the stimuli. Sequential Sensitivity Analysis and the conditional stimulus model did not furnish a complete explanation for these data. A consideration of additional cognitive contrast effects yielded a possible explanation.