Delayed identity matching to complex samples: teaching students with mental retardation spelling and the prerequisites for equivalence classes.

Students with mental retardation learned delayed matching to sample in which some of the trials involved complex sample stimuli, each consisting of a picture and a printed word. A touch to the sample complex removed it from the computer display and produced either picture comparisons or a choice pool of letters. If the comparisons were pictures, selecting the picture identical to the preceding sample was reinforced. If the letters appeared, letter-by-letter construction of the preceding printed word sample was reinforced. The procedure engendered new constructed-response spelling performances to pictures and dictated words as samples. The emergence of relations among different sets of printed words (paired with the same pictures) suggested the formation of equivalence classes. One subject's data suggest that written spelling, oral spelling, and naming also may emerge as byproducts of the intervention.