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Imura, T., & Tomonaga, M. (2003). Perception of depth from shading in infant chimpanzees ( Pan troglodytes). Anim. Cogn., 6(4), 253–258.
Abstract: We investigated the ability to perceive depth from shading, one of the pictorial depth cues, in three chimpanzee infants aged 4-10 months old, using a preferential reaching task commonly used to study pictorial depth perception in human infants. The chimpanzee infants reached significantly more to three-dimensional toys than to pictures thereof and more to the three-dimensional convex than to the concave. Furthermore, two of the three infants reached significantly more to the photographic convex than to the photographic concave. These infants also looked longer at the photographic convex than the concave. Our results suggest that chimpanzees perceive, at least as early as the latter half of the first year of life, pictorial depth defined by shading information. Photographic convexes contain richer information about pictorial depth (e.g., attached shadow, cast shadow, highlighted area, and global difference in brightness) than simple computer-graphic graded patterns. These cues together might facilitate the infants' perception of depth from shading.
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Hayashi, M., & Matsuzawa, T. (2003). Cognitive development in object manipulation by infant chimpanzees. Anim. Cogn., 6(4), 225–233.
Abstract: This study focuses on the development of spontaneous object manipulation in three infant chimpanzees during their first 2 years of life. The three infants were raised by their biological mothers who lived among a group of chimpanzees. A human tester conducted a series of cognitive tests in a triadic situation where mothers collaborated with the researcher during the testing of the infants. Four tasks were presented, taken from normative studies of cognitive development of Japanese infants: inserting objects into corresponding holes in a box, seriating nesting cups, inserting variously shaped objects into corresponding holes in a template, and stacking up wooden blocks. The mothers had already acquired skills to perform these manipulation tasks. The infants were free to observe the mothers' manipulative behavior from immediately after birth. We focused on object-object combinations that were made spontaneously by the infant chimpanzees, without providing food reinforcement for any specific behavior that the infants performed. The three main findings can be summarized as follows. First, there was precocious appearance of object-object combination in infant chimpanzees: the age of onset (8-11 months) was comparable to that in humans (around 10 months old). Second, object-object combinations in chimpanzees remained at a low frequency between 11 and 16 months, then increased dramatically at the age of approximately 1.5 years. At the same time, the accuracy of these object-object combinations also increased. Third, chimpanzee infants showed inserting behavior frequently and from an early age but they did not exhibit stacking behavior during their first 2 years of life, in clear contrast to human data.
Keywords: Age Factors; Animals; Child Development/physiology; Child, Preschool; Cognition/*physiology; Female; Growth; Humans; Imitative Behavior/physiology; Infant; Learning/*physiology; Male; Mothers/*psychology; Motor Skills/*physiology; Pan troglodytes/*growth & development/*psychology; Psychomotor Performance/*physiology; Species Specificity
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Brown, R. F., Houpt, K. A., & Schryver, H. F. (1976). Stimulation of food intake in horses by diazepam and promazine. Pharmacol Biochem Behav, 5(4), 495–497.
Abstract: In two adult horses doses of 0.02-0.03 mg/kg diazepam, intravenously, increased 1 hr intake 54-75% above control levels. Intake was stimulated when the diet was a high grain, calorically dense one and also when the diet was a high fiber, calorically dilute one. Two young rapidly growing weanling horses showed an even more pronounced stimulation of intake. Following diazepam 1 hr intake was increased 105-240% above control lelvels. Promazine at a dose of 0.5 mg/kg also stimulated intake in adult horses, but not as markedly as did diazepam. A transquilizer and a neuroleptic appear to have a stimulatory eff upon short-term intake in horses.
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Bjorklund, D. F., Yunger, J. L., Bering, J. M., & Ragan, P. (2002). The generalization of deferred imitation in enculturated chimpanzees (Pan troglodytes). Anim. Cogn., 5(1), 49–58.
Abstract: Deferred imitation of object-related actions and generalization of imitation to similar but not identical tasks was assessed in three human-reared (enculturated) chimpanzees, ranging in age from 5 to 9 years. Each ape displayed high levels of deferred imitation and only slightly lower levels of generalization of imitation. The youngest two chimpanzees were more apt to generalize the model's actions when they had displayed portions of the target behaviors at baseline, consistent with the idea that learning is more likely to occur when working within the “zone of proximal development.” We argue that generalization of imitation is the best evidence to date of imitative learning in chimpanzees.
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Feist, J. D., & McCullough, D. R. (1975). Reproduction in feral horses. J Reprod Fertil Suppl, (23), 13–18.
Abstract: A behavioural study of feral horses was conducted on the Pryor Mountain Wild Horse Range in the western United States. All 270 horses on the Range were identified individually. The sex ratio was nearly balanced. Foal to adult female ratio was 43-2:100. Morality was concentrated among foals and old horses. Horses were organized as forty-four harem groups each with a dominant stallion, one to two immature stallions, one to three immature mares, one to three adult mares and their yearling and foal offspring, and 23 bachelor groups of one to eight stallions. Harem groups were quite stable year-round because of dominance and leadership by the stallions and group fidelity by mares and their offsring. Most changes occurred during the breeding season and involved immature females. Defeat of dominant stallions was infrequent. Immature males were tolerated because of their submissive behaviour. Bachelor stallion groups were inherently unstable. Mares came into heat after foaling in May/June, and were mated by harem stallions only.
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