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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 1, Issue 3, 1988


Psychobiological Aspects of the Acceleration of Postembryonic Development in the Asynchronous Breeder, Pied Flycatcher ( Ficedula Hypoleuca )

The nest behavior of the pied flycatcher nestlings was studied in the artificially formed broods. Each of two groups of nestlings with an age range of four days were studied. Under optimal food conditions, the last of the nestlings to appear shortened the incubation period by 20-25% so that the whole brood fledged relatively synchronously. During the first half of nest life in the mixed broods younger nestlings got food mainly due to their constant motor activity, manifested in unceasing spontaneous begging, resulting from the constantly increased level of feeding motivation. During the second half of the nest life younger nestlings, due to their high activity level, get even the greater amount of food than the elder chicks. The long-lasting contact of the nestlings of both age groups is necessary for the selectively accelerated development of sensory and motor components of functional systems of early behavior that ensure the survival of younger nestlings and their fledging, synchronous with the older ones. It is suggested that all factors promoting the accelerated development of younger nestlings are present in the natural habitat.

Psychophysical Context Effects in Chickens Gallus Gallus Domesticus ( Hubbards )

A quantitative frame-of-reference ( FR ) model that has been successfully tested in humans was examined in generalization experiments with chickens. In Experiment 1, three groups of two chickens each were trained to discriminate between cubes different in volume and tested with a series of cubes with volumes either below, surrounding, or above the training stimuli. The obtained psychometric functions support the assumption that asymmetrical testing after two stimulus-two response training leads to the changes predicted by the FR model. In Experiment 2 shifts in the context defining the test series were administered by gradually enlarging the distance between training and test stimuli. While context effects were found in both experiments these were more pronounced in Experiment 2. The results support the general hypothesis that perception in animals undergoes context effects similar to those obtained in human subjects.

A Comparison Between Agonistic Behavior of Rats of Wistar and Wezob Strain ( Rattus Norvegicus )

Agonistic behavior of rats of the Wistar and WEzob strain was compared. Two male rats of the same strain or two male-female pairs of the same strain were confronted with each other for a period of one hour. Individuals and pairs were unknown to each other. In the week before the pairs or the single males were placed in the two compartments of a box. By removing a separating panel, encounters could take place. Behavior was videotaped and analyzed afterwards. During the confrontation session, males from pairs displayed far more consummatory acts (clinch fights and attacks, Le., biting or attempting to bite) than the individual housed males. The individually housed males, however, showed overall longer agonistic behavior, but this consisted of mainly appetitive agonistic behavior such as lateral attack, keeping down, keep off lying, them males from pairs. There were striking differences between strains: Wistar males from pairs showed more frequent and longer clinch fights and attacks than those of the WEzob strain. The former got far more wounds. It seems that belonging to the losing strain in interstrain encounters is not a good predictor of the amount of intrastrain aggression. The WEzob females displayed more frequent and longer appetitive behavior than the Wistar females. In male-female interactions the WEzob rats displayed more fi-equently some appetitive behaviors than the Wistar rats, but the Wistar rats displayed more and longer clinch fights than the WEzob rats. The enhancement of male aggression by the presence of a female seems to be a strain -dependent phenomenon.

Sequential Patterns of Behavior in The Black Buck, Antilope Cervicapra ( Linnaeus )

Six male and six female black bucks were observed in the Trivandrum Zoo for one year. Sequential patterns of behavior were homogeneous throughout all observation periods. Sequences were longer with more acts occurring during morning hours than evening hours. However, acts were of shorter duration during noon hours. Sexually dimorphic features were reflected in the behavior sequences. The dominant buck was more active and aggressive than other group members. The behavior sequences of the black bucks are explained in terms of a first order Markov chain with five states. Inhibiting and directing behavior patterns are discussed within an ecological, functional framework.