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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 3, 2000


General Process Learning Theory: Challenges from Response and Stimulus Factors

Traditionally, general theories of learning have focused on associative and other mechanisms that are responsible for conditioned behavior without seriously considering how those mechanisms might vary depending on the stimulus being learned about and the response that provides evidence of learning. Recent studies of sexual conditioning in male domesticated quail have revealed both quantitative and qualitative variations in the functional properties of conditioned behavior depending on the response that is measured and the events or objects that serve as conditioned stimuli. For example, sexually conditioned sign tracking behavior is directly related to the ratio between context exposure (C) and trial duration (T) in a conditioning procedure, but sexually conditioned goal tracking is inversely related to the C/T ratio. Other studies have shown that conditioned stimuli that include limited cues from a female quail support different forms of sexually conditioned behavior than conditioned stimuli that lack female features. Furthermore, these various conditioned responses are differentially sensitive to extinction and reinforcer devaluation. The implications of these findings for general process learning theory are discussed.

Secondary imprinting in the domestic chick: Binocular and lateralized monocular performance

Newly-hatched chicks were reared with a coloured imprinting object on day 1 of life (primary imprinting) and then with an object of a different colour (secondary imprinting) on day 2. They were then tested on day 3 for preferences between the primary and the secondary imprinting object in binocular and in monocular conditions. The main results were that (1) left-eyed chicks usually showed clearer choice than right-eyed chicks; (2) there were colour preferences that appeared to affect choice differently in left- and right-eyed chicks; (3) eye asymmetries were in general more pronounced in males than in females. Experiments using composite stimuli (that contained simultaneously the colours of both the primary and the secondary imprinting objects) and experiments in which retention of memories for the primary and secondary imprinting objects were tested against the preference for novel objects showed that the eye asymmetries cannot be explained neither by hemispheric differences in response to novelty nor by different rates of forgetting of primary and secondary imprinting objects in the two hemispheres. It is argued that properties of single-units responses in neural structures involved in imprinting in the left and right hemisphere can account for these behavioural results.

Renewal of Formerly Conditioned Fear in Rats after Extensive Extinction Training

We explored renewal of formerly acquired and then extinguished fear in rats. After 24 paired trials of a tone and an electric shock, acquired fear to the tone was extinguished in another context by repeated exposure to the tone alone. Conditioned fear was behaviorally extinguished by the 32nd trial of tone exposure; 40 or 80 additional extinction trials (i.e., a total of 72 or 112 extinction trials) were administered to independent groups of rats. Extinguished fear was renewed by testing the tone in the original context, independently of the amount of the preceding extinction training. The finding suggests that this type of fear renewal is difficult to prevent even after extensive extinction training prior to context change. Fear renewal also took place by shifting contexts after 72 extinction trials, when the fear had been extinguished in the context of acquisition. This kind of renewal was, however, prevented by extending extinction training to 112 trials.

Presence of a Familiar Odourant Accelerates Acceptance of Novel Food in Domestic Chicks

A reluctance to accept unfamiliar foods can damage chickens’ welfare and performance. In the present study, chicks were reared on a mash diet presented in hoppers treated with vanillin and acclimatized to a regime of brief food withdrawal and return. At 8 days of age they were presented with the same food in an unfamiliar form (crumbs) when the hoppers had been treated with either vanillin or water. The presence of the familiar odourant accelerated feeding and increased food consumption over a 30 min test. The results are discussed in terms of impaired food recognition, neophobia, and the strategic relevance of olfactory therapy.

Black-and-White Colobus Monkeys (Colobus guereza) do not Show Mirror Self-Recognition

Mirror self-recognition (MSR) has been studied in many species of primates, but not previously in the black-and-white colobus monkey ( Colobus guereza ). A family group of five monkeys was videotaped in a baseline session with clear glass panel and nine sessions (270 min) with a mirror. All monkeys showed substantial interaction with the mirror. The monkeys show evidence of limited use of the mirror’s reflective properties, but no evidence of behaviors indicating MSR. These data are consistent with the failure of other species of monkeys to show MSR and with the hypothesis that great apes are the only species capable of MSR.