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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 13, Issue 1, 2000

Volume 13 Issue 1 2000


Monitoring Spatial Transpositions by Bonobos ( Pan paniscus ) and Chimpanzees ( P. troglodytes )

Two bonobos ( Pan paniscus ) and three chimpanzees ( P. troglodytes ) monitored spatial transpositions, or the simultaneous movement of multiple items in an array, so as to select a specific item from the array. In the initial condition of Experiment 1, food reward was hidden beneath one of four cups, and the apes were required to select the cup containing the reward in order to receive it. In the second condition, the test board on which the cups were located was rotated 180 degrees after placement of the food reward. In the third condition, two of the three cups switched locations with one another after placement of the food reward. All five apes performed at very high levels for these conditions. Experiment 2 was a computerized simulation of the tasks with the cups in which the apes had to track one of four simultaneously moving stimuli on a computer monitor. Two of the three apes that were tested performed at a very high level for this computerized task. Therefore, members of the genus Pan can perform complex feats of spatial monitoring such as transpositions both in real world contexts and in computerized tests.

Interference in Human Predictive Learning when Associations Share a Common Element

Interference between cues is generally regarded as different from interference between outcomes in the (animal and human) predictive learning literature. In consequence, current theories of learning generally attempt to explain one or the other effect but not both. In general, cues are assumed to interfere with each other only if they are trained in compound as predictors of the same outcome, whereas outcomes are assumed to interfere with each other only if they have been individually paired to the same cue. In two experiments with humans, we examined the parallel between interference between elementally-trained cues and between elementally-trained outcomes, using a behavioral preparation. Experiment 1 showed that both interference effects are similarly affected by identical contextual manipulations. Experiment 2 showed that the two effects take place when the interfering association shares an element with the target association: When the shared element is the outcome, interference between cues takes places; when the shared element is the cue, interference between outcomes occurs. These results add to the growing body of evidence that calls for the integrative study of interference between cues and between outcomes in predictive learning situations.

Exploring Adaptations to Famine: Rats Selectively Bred for Differential Intake of Saccharin Differ on Deprivation-Induced Hyperactivity and Emotionality

In many mammals, including humans and rats, acute starvation increases locomotor activity. This seemingly paradoxical and potentially lethal behavior pattern may reflect an evolved, multisystem response to sudden threats to metabolic homeostasis. The present study provides a novel test of this idea. Occidental High- (HiS) and Low- (LoS) Saccharin-Consuming rats differ on the taste phenotype and also on some affective measures, on which LoS rats score higher. Wheel running was measured in HiS and LoS rats with food available freely versus for 1 hr daily. As predicted, restricted feeding stimulated significantly more running among LoS rats. Two independent tests of emotionality (acoustic startle, stress-induced analgesia) also distinguished the lines. The confluence of taste, emotion, and reactivity to starvation conditions in species as distantly related as rats and humans points to integrated biobehavioral systems that warrant further exploration.

The International Society for Comparative Psychology: The First 15 Years

On June 15, 1983 a small group of comparative psychologists from countries around the world met in Toronto, Canada to establish a new Society. The International Society for Comparative Psychology (ISCP) was formally recognized by the Assembly of the International Union of Psychological Sciences at their meeting in Acapulco, Mexico in September 1984. This article describes the founding and organization of the ISCP, and traces the development of the Society over its first 15 years. It also examines the reception of the Society by the comparative psychology community at large and some of the problems it has faced in the past and may face in the future.

Domestic Chicks’ Attraction to Video Images: Effects of Stimulus Movement, Brightness, Colour and Complexity

Video images of screensavers attract domestic chicks. This study identified their attractive attributes. One focal chick in groups of three was observed for 5 min daily on 10 consecutive days from 2 days of age. Chicks spent little time in the end zones of the home box in the absence of video stimulation (Experiment 1). Videos differing in one attribute were then presented simultaneously at opposite ends of the cage. Chicks spent longer near moving than still videos (Experiment 2), bright than dull videos (Experiment 3), coloured than black-and-white videos (Experiment 4), a complex “Fish” screensaver than a simple “Square” screensaver (Experiment 5), and a more complex cartoon than the Fish screensaver (Experiment 6). Repeated exposure increased approach and preferences were strongest for complex stimuli.

Surprising Nonreward Reduces Aggressive Behavior in Rats*

Studies with several mammalian species show that the surprising omission of an appetitive reinforcer invigorates aggressive behavior. In the present experiment, dominant and nondominant individuals within pairs of male rats were identified in pretests sessions. The dominant males were then randomly assigned to one of two groups and trained in a consummatory contrast situation. Group 32-W received exposure to 32% sucrose solution and was then shifted to water; Group W-W received exposure to water throughout the experiment. Immediately after a shift to water, nondominant males were introduced in the training box for a 5-min-long session. The previously dominant males of Group 32-W exhibited a significant decrease in aggressive attacks to nondominant pairmates, compared to the W-W dominant rats. Consummatory training in a situation involving surprising nonreward inhibits aggressive behavior. The potential connection between the present results and those obtained in experiments with inescapable shocks is discussed.