Adaptive staircase methods—A comparison using Markov theory

Adaptive techniques have been widely used for rapid estimation of psychophysical thresholds. This study considers two of the adaptive staircase rules described by Levitt J. Acoust. Soc. Am. 49, 467–477 (1971). A “three-step rule,” in which the level of the signal is increased after an incorrect response and decreased after three successive correct responses, is compared to a “two-step rule,” in which the level is decreased after only two successive correct responses. Each of these rules was modeled in combination with both 2AFC and 3AFC psychophysical procedures using Markov theory. The time required to achieve a certain level of accuracy was then calculated using a digital computer. Both rules in combination with the 3AFC procedure were found to require less time than either rule in combination with the 2AFC procedure. In addition, for a given psychophysical procedure the three-step rule always required less time than the two-step rule. These results will be discussed and compared to the performance of human subjects. Work supported by NINCDS, Grant NS 03856, and Fulbright Commission, Federal Republic of Germany.