Document Type



M. Sidman (1987) and P. F. Carrigan and Sidman (1992) have advised against the use of two-choice procedures in studies of emergent matching to sample. They argue that in two-choice, as opposed to multiple- choice, procedures: (1) It is more difficult to make sure that the baseline conditional relations have been established; (2) There is a greater chance that test outcomes are not related to the baseline conditional relations; and (3) The predictions of stimulus equivalence are less clear. In response to the first two arguments, the author argues that they refer to technical difficulties that can easily be handled within the two- choice procedure itself. In response to the third argument, the author argues that the formulation of Carrigan and Sidman is a new account, that it is inconsistent with the old account of Sidman and W. Tailby (1982), and that the two-choice procedure goes well with the old account. Further, the author argues that there are no strong reasons for adopting the new account, and that the recommendation of using three choices in particular is problematic.