Acquisition and functional use of signing and writing in deaf adults with mental retardation through conditional discrimination

Two deaf adults with mental retardation were trained to establish a stimulus equivalence among object, word, and sign through word-object and sign-object conditional discriminations for new vocabularies. The formation of the functional equivalence relations was tested both in an ordinal "tact" setting and in a "mand" setting. Results showed that: (1) the subjects could learn indirectly sign-word relations; (2) they could demand objects by writing and/or signing the name of objects without direct training of expression when the subjects took the role of the "demander." Moreover, each subject showed a spontaneous change of expressive mode (e.g., signing to writing, writing to signing), when an incorrect object was offered. Also, as the "supplier," each subject reconfirmed the requested object with a mode other than the demander's. These mode changes within and between subjects also represent the formation of a stimulus equivalence among object, word, and sign. The efficacy of the training in new vocabularies, by the combined use of conditional discrimination and the social behavior chain, was discussed for the deaf person with mental retardation.