AUDITORY QUALITY CUES ARE MORE EFFECTIVE THAN AUDITORY LOCATION CUES IN A R-NO-R (GO-NO-GO) DIFFERENTIATION - THE EXTENSION OF THE RULE TO PRIMITIVE MAMMALS (AMERICAN OPOSSUM, DIDELPHIS-VIRGINIANA)

Discrimination learning of instrumental responses to auditory compound stimuli was investigated in opossums using the R no R (go - no go) di fferentiation. Each compound stimulus consisted of two factors: qualit y and location. Each correct response performed to the conditioned pos itive, or ''safe'' stimulus, was rewarded by food and never punished. Each incorrect response performed to the conditioned negative, or ''wa rning'' stimulus, was punished by an electric shock. In subsequent tes ting, each opossum proved to use only the quality cues to solve the ta sk even though later testing showed them capable of using the location cues. Thus, the rule discovered in higher mammals, that the efficacy of auditory stimuli in differentiation depends on the perceptual abili ty of the animal as well as the type of the behavioral response with w hich the animal is confronted, may be extended to neurologically primi tive mammals and also to a joint conditioned approach-avoidance method .