Complex stimulus relations and exclusion in severe mental retardation

Exclusion of stimuli involved in complex stimulus relations was examined in a severely retarded young man. On two-comparison arbitrary auditory-visual matching-to-sample trials, the subject learned first to select (a) either of two different food items in response to the same spoken-name sample of (b) the same food item in response to either of two different spoken names. Then, on exclusion test trials, a food involved in one or the other type of relation was displayed with a novel food (i.e., one not yet related to a name); the spoken-name sample was also novel. On such trials, the subject selected the novel food, apparently excluding the food involved in learned relations. The study systematically replicates and extends research on exclusion performance of low-functioning mentally retarded individuals and provides additional data on relational learning in this population.