Abstract: The aim of this study was to test the existence of a “reactivity-to-humans” trait which is stable over time and across situations. For this purpose, four test situations were repeated on the same animals at 8 months, 1.5 years (N = 110 horses) and 2.5 years of age (N = 54 horses). These situations involved a “familiar passive human test” during which a familiar person stayed motionless in the test pen, a “familiar active human test” and an “unfamiliar active human test” during which a familiar or unfamiliar person attempted to touch the horse, and a “halter-fitting and heart-rate measurement test”, during which the horse was haltered and equipped with a surcingle and then had its heart-rate measured. Many behavioural variables were recorded during the tests, and correlations between ages and variables measured during other situations were investigated. When correlations were found, we concluded that the variables corresponded to temperament traits which are stable over time and across situations. The horses tested were divided into four groups according to breed (Anglo-Arab and Welsh) and year of birth (2001 and 2002). Data for each group were analysed separately with Spearman rank correlations. Regarding stability over time, there was a strong correlation between ages in the frequency of licking/nibbling the passive human, the time taken by a familiar or unfamiliar person to touch the horse, and the time taken to fit a halter (e.g. the time taken to touch the horse's muzzle was significantly correlated between ages in 7 out of the 8 possible cases: 0.40 <= R <= 0.67). Regarding stability across situations, results indicate that the more frequently a horse sniffed, licked or nibbled a passive human, the easier it was for either a familiar or unfamiliar active human to touch and halter it. Moreover, a horse which could be touched easily by a familiar human could also be touched and haltered easily by an unfamiliar human. These behaviours, which are linked directly to humans, therefore indicate good stability over time and across situations. In conclusion, this stability suggests the existence of a “reactivity-to-humans” temperament trait, whether the human is passive or active, familiar or unfamiliar. When the animals do not have frequent contact with humans, this reactivity is stable over time and can be measured as early as 8 months of age using the behavioural variables cited above.

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.

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.

Abstract: The concept of personality implies individual differences in behavior and physiology that show some degree of repeatability/consistency over time and across contexts. Most studies of animal personality, particularly studies of individuals' variation in physiological mechanisms, have been conducted on selected individuals in controlled conditions. We attempted to detect consistent behaviors as well as physiological patterns in greylag ganders (Anser anser) from a free-roaming flock living in semi-natural conditions. We tested 10 individuals repeatedly, in a handling trial, resembling tests for characterization of “temperaments” in captive animals. We recorded the behavior of the same 10 individuals during four situations in the socially intact flock: (1) a “low density feeding condition”, (2) a “high density feeding condition”, (3) a “low density post-feeding situation” and (4) while the geese rested. We collected fecal samples for determination of excreted immuno-reactive corticosterone (BM) and testosterone metabolites (TM) after handling trials, as well as the “low density feeding” and the “high density feeding” conditions. BM levels were very highly consistent over the repeats of handling trials, and the “low density feeding condition” and tended to be consistent over the first two repeats of the “high density feeding condition”. Also, BM responses tended to be consistent across contexts. Despite seasonal variation, there tended to be inter-test consistency of TM, which pointed to some individual differences in TM as well. Aggressiveness turned out to be a highly repeatable trait, which was consistent across social situations, and tended to correlate with an individual's resistance during handling trials. Also, “proximity to the female partner” and “sociability” – the average number of neighboring geese in a close distance while resting – were consistent. We conclude that aggressiveness, “affiliative tendencies” and levels of excreted corticosterone and testosterone metabolites may be crucial factors of personality in geese.

Abstract: The purpose of this study was to ascertain the frequency of gambling involvement and the prevalence of problem gambling among horse race gamblers and to discover whether problem gambling in this sample is associated with a history of trauma. Among a sample of 266 South African horse-race gamblers (94% men and 6% women, Mage 46.8 yr., SD = 13.9, range 18-85 years), 31.2% were classified as probable pathological gamblers and 19.9% with problem gambling. Major weekly gambling activities included racetrack betting (82%), purchase of lottery tickets or scratch tickets (35%), purchase of sports lottery tickets (23%), and using casino type games (18%). Trauma history was significantly associated with gambling severity.