Equivalence classes in individuals with minimal verbal repertoires

Studies from two different laboratories tested for equivalence classes in i ndividuals with severe mental retardation and minimal verbal repertoires. i n the first study, 3 individuals learned several matching-to-sample perform ances: matching picture comparison stimuli to dictated-word sample stimuli (AB), matching those same pictures to printed letter samples (CB), and also matching the pictures to nonrepresentative forms (DB). On subsequent tests , all individuals immediately displayed Emergent Relations AC, AD, BC, ED, CD, and DC, together constituting a positive demonstration of equivalence ( as defined by Sidman). The second study obtained a positive equivalence tes t outcome in 1 of 2 individuals with similarly minimal verbal repertoires. Taken together, these studies call into question previous assertions that e quivalence classes are demonstrable only in individuals with well-developed language repertoires.