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Drent, P. J., van Oers, K., & van Noordwijk, A. J. (2003). Realized heritability of personalities in the great tit (Parus major). Proc Biol Sci, 270(1510), 45–51.
Abstract: Behaviour under conditions of mild stress shows consistent patterns in all vertebrates: exploratory behaviour, boldness, aggressiveness covary in the same way. The existence of highly consistent individual variation in these behavioural strategies, also referred to as personalities or coping styles, allows us to measure the behaviour under standardized conditions on birds bred in captivity, link the standardized measurements to the behaviour under natural conditions and measure natural selection in the field. We have bred the great tit (Parus major), a classical model species for the study of behaviour under natural conditions, in captivity. Here, we report a realized heritability of 54 +/- 5% for early exploratory behaviour, based on four generations of bi-directional artificial selection. In addition to this, we measured hand-reared juveniles and their wild-caught parents in the laboratory. The heritability found in the mid-offspring-mid-parent regression was significantly different from zero. We have thus established the presence of considerable amounts of genetic variation for personality types in a wild bird.
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Zentall, T. R., & Kaiser, D. H. (2005). Interval timing with gaps: gap ambiguity as an alternative to temporal decay. J Exp Psychol Anim Behav Process, 31(4), 484–486.
Abstract: C. V. Buhusi, D. Perera, and W. H. Meck (2005) proposed a hypothesis of timing in rats to account for the results of experiments that have used the peak procedure with gaps. According to this hypothesis, the introduction of a gap causes the animal's memory for the pregap interval to passively decay (subjectively shorten) in direct proportion to the duration and salience of the gap. Thus, animals should pause with short, nonsalient gaps but should reset their clock with longer, salient gaps. The present authors suggest that the ambiguity of the gap (i.e., the similarity between the gap and the intertrial interval in both appearance and relative duration) causes the animal to actively reset the clock and prevents adequate assessments of the fate of timed intervals prior to the gap. Furthermore, when the intertrial interval is discriminable from the gap, the evidence suggests that timed intervals prior to the gap are not lost but are retained in memory.
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van Niekerk, H. P. (1980). Ethological studies within the man-horse relationship. J S Afr Vet Assoc, 51(4), 237–238.
Abstract: Certain aspects of ethology and the horse's senses are discussed to bring about a better understanding between man and horse. Furthermore the behaviour of horses with respect to housing, feeding, breeding, veterinary treatment and work are considered.
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Tommasi, L., & Vallortigara, G. (2000). Searching for the center: spatial cognition in the domestic chick (Gallus gallus). J Exp Psychol Anim Behav Process, 26(4), 477–486.
Abstract: Chicks learned to find food hidden under sawdust by ground-scratching in the central position of the floor of a closed arena. When tested inan arena of identical shape but a larger area, chicks searched at 2 different locations, one corresponding to the correct distance (i.e., center) in the smaller (training) arena and the other to the actual center of the test arena. When tested in an arena of the same shape but a smaller area, chicks searched in the center of it. These results suggest that chicks are able to encode information on the absolute and relative distance of the food from the walls of the arena. After training in the presence of a landmark located at the center of the arena, animals searched at the center even after the removal of the landmark. Marked changes in the height of the walls of the arena produced some displacement in searching behavior, suggesting that chicks used the angular size of the walls to estimate distances.
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Parish, A. R., & De Waal, F. B. (2000). The other “closest living relative”. How bonobos (Pan paniscus) challenge traditional assumptions about females, dominance, intra- and intersexual interactions, and hominid evolution. Ann N Y Acad Sci, 907, 97–113.
Abstract: Chimpanzee (Pan troglodytes) societies are typically characterized as physically aggressive, male-bonded and male-dominated. Their close relatives, the bonobos (Pan paniscus), differ in startling and significant ways. For instance, female bonobos bond with one another, form coalitions, and dominate males. A pattern of reluctance to consider, let alone acknowledge, female dominance in bonobos exists, however. Because both species are equally “man's” closest relative, the bonobo social system complicates models of human evolution that have historically been based upon referents that are male and chimpanzee-like. The bonobo evidence suggests that models of human evolution must be reformulated such that they also accommodate: real and meaningful female bonds; the possibility of systematic female dominance over males; female mating strategies which encompass extra-group paternities; hunting and meat distribution by females; the importance of the sharing of plant foods; affinitive inter-community interactions; males that do not stalk and attack and are not territorial; and flexible social relationships in which philopatry does not necessarily predict bonding pattern.
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DiGian, K. A., Friedrich, A. M., & Zentall, T. R. (2004). Discriminative stimuli that follow a delay have added value for pigeons. Psychon Bull Rev, 11(5), 889–895.
Abstract: Clement, Feltus, Kaiser, and Zentall (2000) reported that pigeons prefer discriminative stimuli that require greater effort (more pecks) to obtain over those that require less effort. In the present experiment, we examined two variables associated with this phenomenon. First, we asked whether delay of reinforcement, presumably a relatively aversive event similar to effort, would produce similar effects. Second, we asked whether the stimulus preference produced by a prior relatively aversive event depends on its anticipation. Anticipation of delay was accomplished by signaling its occurrence. Results indicated that delays can produce preferences similar to those produced by increased effort, but only if the delays are signaled.
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Baum, M. J. (2006). Mammalian animal models of psychosexual differentiation: when is 'translation' to the human situation possible? Horm Behav, 50(4), 579–588.
Abstract: Clinical investigators have been forced primarily to use experiments of nature (e.g., cloacal exstrophy; androgen insensitivity, congenital adrenal hyperplasia) to assess the contribution of fetal sex hormone exposure to the development of male- and female-typical profiles of gender identity and role behavior as well as sexual orientation. In this review, I summarize the results of numerous correlative as well as mechanistic animal experiments that shed significant light on general neuroendocrine mechanisms controlling the differentiation of neural circuits controlling sexual partner preference (sexual orientation) in mammalian species including man. I also argue, however, that results of animal studies can, at best, provide only indirect insights into the neuroendocrine determinants of human gender identity and role behaviors.
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Flack, J. C., de Waal, F. B. M., & Krakauer, D. C. (2005). Social structure, robustness, and policing cost in a cognitively sophisticated species. Am Nat, 165(5), E126–139.
Abstract: Conflict management is one of the primary requirements for social complexity. Of the many forms of conflict management, one of the rarest and most interesting is third-party policing, or intervening impartially to control conflict. Third-party policing should be hard to evolve because policers personally pay a cost for intervening, while the benefits are diffused over the whole group. In this study we investigate the incidence and costs of policing in a primate society. We report quantitative evidence of non-kin policing in the nonhuman primate, the pigtailed macaque. We find that policing is effective at reducing the intensity of or terminating conflict when performed by the most powerful individuals. We define a measure, social power consensus, that predicts effective low-cost interventions by powerful individuals and ineffective, relatively costly interventions by low-power individuals. Finally, we develop a simple probabilistic model to explore whether the degree to which policing can effectively reduce the societal cost of conflict is dependent on variance in the distribution of power. Our data and simple model suggest that third-party policing effectiveness and cost are dependent on power structure and might emerge only in societies with high variance in power.
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Plotnik, J. M., de Waal, F. B. M., & Reiss, D. (2006). Self-recognition in an Asian elephant. Proc. Natl. Acad. Sci. U.S.A., 103(45), 17053–17057.
Abstract: Considered an indicator of self-awareness, mirror self-recognition (MSR) has long seemed limited to humans and apes. In both phylogeny and human ontogeny, MSR is thought to correlate with higher forms of empathy and altruistic behavior. Apart from humans and apes, dolphins and elephants are also known for such capacities. After the recent discovery of MSR in dolphins (Tursiops truncatus), elephants thus were the next logical candidate species. We exposed three Asian elephants (Elephas maximus) to a large mirror to investigate their responses. Animals that possess MSR typically progress through four stages of behavior when facing a mirror: (i) social responses, (ii) physical inspection (e.g., looking behind the mirror), (iii) repetitive mirror-testing behavior, and (iv) realization of seeing themselves. Visible marks and invisible sham-marks were applied to the elephants' heads to test whether they would pass the litmus “mark test” for MSR in which an individual spontaneously uses a mirror to touch an otherwise imperceptible mark on its own body. Here, we report a successful MSR elephant study and report striking parallels in the progression of responses to mirrors among apes, dolphins, and elephants. These parallels suggest convergent cognitive evolution most likely related to complex sociality and cooperation.
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Stamps, J. A. (2007). Growth-mortality tradeoffs and 'personality traits' in animals. Ecol Lett, 10(5), 355–363.
Abstract: Consistent individual differences in boldness, reactivity, aggressiveness, and other 'personality traits' in animals are stable within individuals but vary across individuals, for reasons which are currently obscure. Here, I suggest that consistent individual differences in growth rates encourage consistent individual differences in behavior patterns that contribute to growth-mortality tradeoffs. This hypothesis predicts that behavior patterns that increase both growth and mortality rates (e.g. foraging under predation risk, aggressive defense of feeding territories) will be positively correlated with one another across individuals, that selection for high growth rates will increase mean levels of potentially risky behavior across populations, and that within populations, faster-growing individuals will take more risks in foraging contexts than slower-growing individuals. Tentative empirical support for these predictions suggests that a growth-mortality perspective may help explain some of the consistent individual differences in behavioral traits that have been reported in fish, amphibians, reptiles, and other animals with indeterminate growth.
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