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Open Access Publications from the University of California


The International Journal of Comparative Psychology is sponsored by the International Society for Comparative Psychology. It is a peer-reviewed open-access digital journal that publishes studies on the evolution and development of behavior in all animal species. It accepts research articles and reviews, letters and audiovisual submissions.

Volume 35, 2022

Research Article

Effect of qualitatively varied reinforcement on response rates using substitutable consequences

In order to test the effects of qualitatively varied reinforcement on response rates 3 experiments were conducted. The goal of the first experiment was asses the level of substitutability between two reinforcers   8 female Wistar rats kept on a diet consisting solely of turnip and millet seeds, subjects were exposed to a concurrent FR5 FR5 and then to a FR4 FR8 program, by the end of the experiment there was a swift in consumption, albeit to a small degree. During the second experiment, 8 female Wistar Rats were exposed to a three-component variable interval program which consisted of three components; one during which only millet seeds were available, one in which only turnip seeds were available and a third component in which both kinds of seeds were delivered randomly. By the end of the experiment the highest response rates were recorded during the component in which only millet seeds were available. Finally, a Third experiment was implemented in order to assess whether the particular way in which the substitutable consequences are delivered (i.e., random or simultaneously) has an effect on response rates. The program for this experiment consisted of a VI 60`s with two components. During one of the components a mixture of millet seeds was delivered when subjects responded after the interval was reached while during the second component either millet and turnip seeds were delivered randomly. By the end of the experiment no differences between components were found.  Results are discussed in terms of their implications for the study of reinforcement.

  • 3 supplemental ZIPs

A Comprehensive Description of Intake of Diverse Foods By Rats (Rattus norvegicus) Selectively Bred on a Taste Phenotype

Eating is a central feature of the lives of opportunistic omnivores such as humans and Norway rats. Yet in most laboratory research with Rattus norvegicus, the food landscape is monotonous, and the studies utilizing a variety of foods shed little light on intake of individual foods or choice behavior. The present study provides the most comprehensive description to date of female and male laboratory rats’ intake of foods that they and humans encounter outside of the laboratory. In eleven experiments, test foods included varieties of peanut butter, cheese, cookies, meat, chocolate, fruits, and vegetables. Rats were given commercial products or custom versions that controlled for proportion of calories from fat and caloric density, one or two foods at a time. A final experiment examined pure macronutrient self-selection. Intraspecies diversity was modeled with rat lines selectively bred on a taste phenotype. All groups voluntarily ate every food, with intake (in grams) highest for vegetables and lowest for pure macronutrients. When Low- (LoS) and High-Saccharin-Consuming (HiS) rats differed, LoS rats ate more meat and fat and were choosier whereas HiS rats ate high-carbohydrate foods more avidly; exceptions and sex-dependent differences occurred. Using these results to enrich the food landscape for laboratory rats can enhance the comparative study of food intake and its relation to other behavioral systems.

Relationship between Monetary reward and Athletic Identity of Lagos State Athletes

This study investigated the relationship between monetary reward and athletes’ athletic identity. The purpose was to understand the difference in athletic identity between athletes who earned monetary compensations and those who did not earn any monetary compensations for participating in sports. Two hundred and fifty-six athletes who competed in state-organized sports competitions completed the Athletic Identity Measurement Scale (AIMS). The data collected was analyzed using Mann Whitney U tests and Linear Regression at 0.05 level of significance. The findings revealed that age did not predict athletic identity, and monetary reward did not differentiate athletes who received financial compensations or not based on their athletic identity. The results have confirmed that other factors that are not monetary may be associated with athletes’ athletic identity. Therefore sports psychologists should identify those factors to help athletes sustain their athletic personalities.