Misconceptions about classical psychophysics and the measurement of response bias.

Misconceptions exist about the ability of classical psychophysical techniques to measure separately the sensory and nonsensory (response bias) factors in a discrimination task. The views of the early researchers in psychophysics are reviewed. The manner in which the method of constant stimuli gives separate measures of sensory sensitivity and response bias is illustrated. Modern derivatives of classical psychophysical techniques which estimates sensory and nonsensory components are described. Finally, data indicating a correspondence between sensory and nonsensory factors obtained with various psychological techniques are reviewed.