Adaptive procedures adjust stimulus intensity based on prior responses and converge on thresholds

Evidence

Adaptive Procedures. Whereas in classic forced-choice procedures the stimuli to be presented are chosen by the experimenter, in adaptive procedures the stimulus presented in a trial depends on the answers given by the subject in preceeding trials. These procedures are also called “up-down” procedures. If, for instance, the absolute threshold is measured in an adaptive procedure, then the sound pressure is lowered until it can be taken for granted, that the subject doesn’t hear the stimulus. The sound pressure is then increased until the subject clearly hears the stimulus, and after that it is again decreased. The step size is reduced with the number of reversals. When a predetermined small step size is reached, a value can be calculated with an accuracy of half the final step size by averaging the last few reversals. This means that adaptive procedures show some similarity to the method of tracking, because they yield a final value without the explicit use of psychometric functions. — Professor Dr.-Ing. Hugo Fastl, Professor Dr.-Ing. Eberhard, Psychoacoustics- Facts and Models, 117

Categorization

• DEFINE: Clearly defines adaptive/up-down procedures and how threshold estimation works.