Motivational specificity of the signal value of odor cues: a reconsideration and extension.

Abstract

For over fifteen years, numerous studies utilizing a straight runway apparatus have demonstrated that rat subjects exude either quatitatively and/or qualitatively different odors on reward (R) and nonreward (N) occasions. Interestingly, several studies have provided substantial evidence that Rand N odors exuded by rat subjects tested under different deprivation conditions are quantitatively and/or qualitatively different, suggesting motivational specificity (i.e., runway trained rat subjects deprived of food will not attend to or utilize odor cues exuded by startbox placed, water-deprived odor-donor rats and vice versa). The present studies were designed to further investigate the contention of strict motivational specificity of conspecific odor cues. Additionally, other parameters were addressed which might interact with and/or influence the utilization of Rand N odors for both food-and water-deprived animals. Experiment 1 administered the same reinforcer (32% sucrose-water) to squads of rat subjects experiencing the different deprivation conditions. The results indicated that runway trained rats tested under one deprivation state exuded odors that were effectively utilized by subsequent animals being tested under a different deprivation state. Similar results were obtained in Experiment 2 when the squad size was smaller and a more substantial reinforcer was employed (32% sucrose-milk). The results of both Experiments land 2 strongly suggested that individual, natural animal odors may play some role in the runway behavior of the rat. This contention was further supported by the results of Experiments 3 and 4 when more traditional reinforcers Were employed (i.e., food-deprived animals received food pellets and water-deprived animals received water). Moreover, Experiments 3 and 4 provided evidence that odors, exuded by water deprived rats may be less intense and/or salient than odors exuded by food-deprived subjects. Taken collectively, the present studies seriously question the conception of strict motivational specificity with regard to the signal value of odor cues. The apparently discrepant results are discussed in terms of the particular experimental designs employed.