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Reddon, A. R., & Hurd, P. L. (2009). Acting unilaterally: Why do animals with strongly lateralized brains behave differently than those with weakly lateralized brains? Bioscience Hypotheses, 2(6), 383–387.
Abstract: Cerebral lateralization was once thought to be unique to humans, but is now known to be widespread among the vertebrates. Lateralization appears to confer cognitive advantages upon those that possess it. Despite the taxonomic ubiquity and described advantages of lateralization, substantial individual variation exists in all species. Individual variation in cerebral lateralization may be tied to individual variation in behaviour and the selective forces that act to maintain variation in behaviour may also act to maintain variation in lateralization. The mechanisms linking individual variation in the strength of cerebral lateralization to individual variation in behaviour remain obscure. We propose here a general hypothesis which may help to explain this link. We suggest that individuals with strong and weak lateralizations behave differently because of differences in the ability of one hemisphere to inhibit the functions of the other in each type of brain organization. We also suggest a specific mechanism involving the asymmetric epithalamic nucleus, the habenula. We conclude by discussing some predictions and potential tests of our hypothesis.
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Graf, P., König von Borstel, U., & Gauly, M. (2013). Importance of personality traits in horses to breeders and riders. Journal of Veterinary Behavior: Clinical Applications and Research, 8(5), 316–325.
Abstract: Abstract Especially in horses, personality traits play an important role because horses' behavior influences their quality as a riding partner. In contrast to that, no objective assessment of horses' personality traits is available at present. Although initial efforts are made in this field, a successful implementation of behavior tests into horse performance tests depends on the acceptance of the riders and breeders. Therefore, the aim of the present study was to assess the importance of personality traits to breeders and riders as well as the degree of riders' acceptance of a temperament test as a more objective means of assessing equine personality traits. Using a web-based survey consisting of a 41-item questionnaire, a total of 1087 competition riders (49.3%), breeders (39.0%), leisure riders (37.9%), and professional riders (8.6%) of 13 countries were recruited to participate in the survey. When asked to split 1000 Euro among the different traits listed in the breeding goal, respondents clearly assigned more weight to the personality-related character and temperament traits (least squares mean ± standard error; P < 0.005: €228.7 ± 17.6) and willingness to work (€123.0 ± 9.6) compared with performance traits, such as the quality of trot (€77.7 ± 6.9) or show jumping (€68.0 ± 12.3). Nevertheless, expected differences in relative weighting of traits between the different groups of riders were confirmed (e.g., character and temperament: €209.3 ± 6.1 [leisure riders] vs. €149.7 ± 5.4 [competition riders], P < 0.0001). When asking why personality traits are so important, the simplification of daily work with the horses (47.9%) and relationship between horse and human (44.9%) as well as a more comfortable and safer handling (31.5%) were most commonly listed. As much as 45.6% of all participants see quality problems with the current assessment and suggested the evaluation of all breeding animals (30.1%), followed by a better standardization of assessment procedures (25.5%) and a move to more objective criteria such as the introduction of a temperament test (20.3%) for solving the problems. The present survey revealed that behavior traits are very important to all groups of riders and breeders, although there are diverse opinions about it. According to the participants, there is a need for and a high potential in the move toward more objective assessment methods of horses' personality traits, and participants would support a restructuring of the current assessment.
Keywords: survey; personality; temperament; horse; rider; breeder
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Graf, P., König von Borstel, U., & Gauly, M. (2014). Practical considerations regarding the implementation of a temperament test into horse performance tests: Results of a large-scale test run. Journal of Veterinary Behavior: Clinical Applications and Research, 9(6), 329–340.
Abstract: Abstract Considering the ever-growing demand of various breeding organizations for an objective, inexpensive, reliable, and easily conducted assessment of the behavior of horses, the aim of our study was to implement a novel-object test and a startling test into any kind of breeding performance testing to assess horses' temperament. Additionally, the influence of testing areas (familiar or unfamiliar), riders, and horse factors such as levels of training, breed, and age were of interest. Furthermore, recommendations for the practical implementation concerning the parameters should be given. Therefore, 1,028 horses over a period of 3 years participated in a temperament test consisting of 5 different stimuli. The horses were either ridden (61.8 %) or led by hand (38.2 %) by an unfamiliar professional rider (N = 43) or a familiar rider (N = 20). Live behavioral observations were taken by a trained observer. Overall, horses' scores for reactivity in the present temperament test were distributed over the whole scale, with lower means and higher standard deviations (6.7 ± 2.2-7.6 ± 2.1) than corresponding scores from the conventional personality evaluation in performance tests (7.7 ± 0.8-8.2 ± 0.5; P < 0.01). High correlations (r = 0.3-0.9; P < 0.001) between the scores for reactivity and the other behavioral parameters (emotional expression, activity, time to calm down, rider's aids) show a large influence of these parameters in assessing the horses' temperament. Factors like breed type, sex, and age had significant influences (P < 0.001) on different scores of the temperament test. In most cases, the rider or handler had no influence on the different scores assessed during the temperament test. The training level and the testing modus never had a significant influence on different scores. Only the testing station or location had a small influence on the scores for the stimulus “bridge” in some horses. Based on the results, it could be concluded that an implementation of a temperament tests into performance testing is possible during various types of testing procedure. Especially the assessment of reactivity, emotional expression, interest in the stimulus and rider's aids during and after passing the stimulus, as well as the time to calm down are important parameters for analyzing the horses' personality.
Keywords: novel object test; temperament; personality; horse; performance traits; performance tests
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Wolf, M., van Doorn, G. S., Leimar, O., & Weissing, F. J. (2007). Life-history trade-offs favour the evolution of animal personalities. Nature, 447(7144), 581–584.
Abstract: In recent years evidence has been accumulating that personalities are not only found in humans but also in a wide range of other animal species. Individuals differ consistently in their behavioural tendencies and the behaviour in one context is correlated with the behaviour in multiple other contexts. From an adaptive perspective, the evolution of animal personalities is still a mystery, because a more flexible structure of behaviour should provide a selective advantage. Accordingly, many researchers view personalities as resulting from constraints imposed by the architecture of behaviour (but see ref. 12). In contrast, we show here that animal personalities can be given an adaptive explanation. Our argument is based on the insight that the trade-off between current and future reproduction often results in polymorphic populations in which some individuals put more emphasis on future fitness returns than others. Life-history theory predicts that such differences in fitness expectations should result in systematic differences in risk-taking behaviour. Individuals with high future expectations (who have much to lose) should be more risk-averse than individuals with low expectations. This applies to all kinds of risky situations, so individuals should consistently differ in their behaviour. By means of an evolutionary model we demonstrate that this basic principle results in the evolution of animal personalities. It simultaneously explains the coexistence of behavioural types, the consistency of behaviour through time and the structure of behavioural correlations across contexts. Moreover, it explains the common finding that explorative behaviour and risk-related traits like boldness and aggressiveness are common characteristics of animal personalities.
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Bell, A. M. (2007). Evolutionary biology: animal personalities (Vol. 447).
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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.
Keywords: Animals; Behavior, Animal; *Growth; *Mortality; *Personality
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Valenchon, M., Lévy, F., Górecka-Bruzda, A., Calandreau, L., & Lansade, L. (2013). Characterization of long-term memory, resistance to extinction, and influence of temperament during two instrumental tasks in horses. Animal Cognition, 16(6), 1001–1006.
Abstract: The present study investigated the influence of temperament on long-term recall and extinction of 2 instrumental tasks in 26 horses. In the first task (backward task), horses learned to walk backward, using commands given by an experimenter, in order to obtain a food reward. In the second task (active avoidance task), horses had to cross an obstacle after a bell rang in order to avoid emission of an air puff. Twenty-two months after acquisition, horses exhibited perfect recall performance in both tasks. Accordingly, no influence of temperament on recall performance could be observed for either task. In contrast, in the absence of positive or negative outcomes, the horses’ ability to extinguish their response to either task was highly variable. Resistance to extinction was related to some indicators of temperament: The most fearful horses tended to be the most resistant to extinction in the backward task, while the least sensitive horses tended to be the most resistant to extinction in the active avoidance task. These findings reveal extensive long-term memory abilities in horses and suggest an influence of temperament on learning processes other than acquisition.
Keywords: Personality; Learning; Individuality; Fearfulness; Equid; Cognitive flexibility
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Sackman, J. E., & Houpt, K. A. (2018). Equine Personality: Association with Breed, Use and Husbandry Factors. Journal of Equine Veterinary Science, .
Abstract: Abstract
Temperament can be defined as innate properties of the nervous system whereas personality includes the complex behavioral traits acquired through life. Association between personality and behavior is important for breeding, selection, and training of horses. For the first time, we evaluated if equine personality components previously identified in Japan and Europe were consistent when applied to American horses. We examined the association of personality with breed, age, sex, management, training, stereotypies and misbehaviors. Materials and Methods The owner directed personality survey consisted of 25 questions. An online version of the survey was created. The principal component analysis (PCA) method was used to associate behavioral traits with personality components. Factor analysis with orthogonal transformation was performed on scores for personality related questions. Results 847 survey responses were used. Quarter horses, “other” breed and Thoroughbred were the most common breeds. Three principal personality components were extracted as each behavioral trait belonged to one of these three components. Arabians, Thoroughbreds, Saddlebreds and Walking horses were the most nervous and Quarter horses, Paints, Appaloosas and Drafts were the least nervous. No trained discipline was significantly associated with any personality component. There were no significant associations between stereotypies and misbehaviors and nervous or curious personality. Conclusions For the first time in predominantly American horses, we have evaluated personality components and their association with breed, age, sex, training discipline and stereotypies. We refute links between personality and trained discipline and confirm the lack of association between nervous personality and stereotypies and misbehaviors. |
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Lilienfeld, S. O., Gershon, J., Duke, M., Marino, L., & de Waal, F. B. (1999). A preliminary investigation of the construct of psychopathic personality (psychopathy) in chimpanzees (Pan troglodytes). J Comp Psychol, 113(4), 365–375.
Abstract: Although the construct of psychopathy has received considerable attention in humans, its relevance to other animals is largely unknown. We developed a measure of psychopathy for use in chimpanzees (Pan troglodytes), the Chimpanzee Psychopathy Measure (CPM), and asked 6 raters to complete this index on 34 chimpanzees. The CPM (a) demonstrated satisfactory interrater reliability and internal consistency; (b) exhibited marginally significant sex differences (males > females); (c) correlated positively with measures of extraversion, agreeableness, and observational ratings of agonism, sexual activity, daring behaviors, teasing, silent bluff displays, and temper tantrums, and negatively with observational ratings of generosity; and (d) demonstrated incremental validity above and beyond a measure of dominance. Although further validation of the CPM is needed, these findings suggest that the psychopathy construct may be relevant to chimpanzees.
Keywords: Age Factors; Analysis of Variance; Animals; Antisocial Personality Disorder/*diagnosis/psychology; Ethology/*methods; Female; Male; Observer Variation; Pan troglodytes/*psychology; Psychiatric Status Rating Scales/*standards; Reproducibility of Results; Sex Characteristics; *Social Behavior
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Gosling, S. D. (1998). Personality dimensions in spotted hyenas (Crocuta crocuta). J Comp Psychol, 112(2), 107–118.
Abstract: Personality ratings of 34 spotted hyenas (Crocuta crocuta) were made by 4 observers who knew the animals well. Analyses suggest that (a) hyena personality traits were rated with generally high reliability; (b) 5 broad dimensions (Assertiveness, Excitability, Human-Directed Agreeableness, Sociability, and Curiosity) captured about 75% of the total variance; (c) this dimensional structure could not be explained in terms of dominance status, sex, age, or appearance; and (d) as expected, female hyenas were more assertive than male hyenas. Comparisons with previous research provide evidence for the cross-species generality of Excitability, Sociability, and especially Assertiveness. Discussion focuses on methodological issues in research on animal personality and on the potential contributions this research can make for understanding the biological and environmental bases of personality.
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