Aversive conditioning of naturally produced reward and nonreward odors in rats

Past experiments have reported that rats encountering reward (R) or nonreward (N) goal events emit odors that can be utilized as discriminative stimuli for instrumental behavior by conspecifics. In the present study, thirsty male rats were aversively conditioned by ingestional toxicosis to R and N odors, and their suppression of water consumption in the presence of these odors was measured. Thirsty trained donors were placed into chambers containing R or N goal events to generate, respectively, the R or N odors. Test animals were given eight differential conditioning trials (four with one odor as CS+; four with the other as CS?), involving placement into an odorcontaining chamber with water available, followed by a LiCl injection on CS+ trials. Animals tested in their CS+ odor consumed significantly less water than did CS? and control subjects. Both R and N odors were conditioned by aversive means and readily discriminable from each other. This represents the first laboratory demonstration of aversive conditioning of such naturally produced odors, and it suggests that aversive conditioning may be useful in the study of odorous emissions generally. Implications for innate meanings of R and N odors are discussed.