Now that the methods of signal detection theory have been presented, it remains to put them into the context of experimental psychology. To do this it will be necessary to discuss a number of procedures called psychophysical methods which have been in use in psychology since the time of Fechner in the second half of the nineteenth century. Psychophysical methods are a number of more or less standard techniques for collecting data in perceptual and learning tasks. Yes-no, rating scale, and forced-choice tasks are psychophysical methods, but the measures which have been extracted from them by signal detection theory differ from those of so-called classical psychophysics.