Conspecific images as elements of compound stimuli controlling operant responding in female rhesus monkeys

Six adult female rhesus monkeys (Macaca mulatta) performed food-reinforced button presses in a compound stimulus discrimination paradigm. Three subjects were trained on a compound stimulus consisting of a color motion picture of an adult male rhesus superimposed over a homogeneous blue field of color. A second group of three subjects was trained on a compound consisting of a color slide depicting an adult male rhesus and the blue field. Subsequent testing of relative stimulus control exerted by either compounds, conspecific stimuli (movie-slide) or blue field alone was carried out. Results indicated that for the movie group, stimulus control was attenuated when either the conspecific stimulus or blue field was presented as a single S+ stimulus compared to tests using the compound stimulus as S+. Subjects in the movie group shared attention to both constituent elements of the compound. Statistically significant differences in stimulus control between compound, conspecific stimulus, and blue field were not found for the slide group. Superior control by the compound movie-blue field was explained as the result of increased visual salience of an altered (blue) conspecific image.