Abstract: The pressures of developing and maintaining intricate social relationships may have led to the evolution of enhanced cognitive abilities in many nonhuman primates. Knowledge of the dominance ranks and social relationships of other individuals, in particular, is important in evaluating one's position in the rank hierarchy and affiliative networks. Triadic interactions offer an excellent opportunity to examine whether decisions are taken by individuals on the basis of such knowledge. Allogrooming supplants among wild female bonnet macaques (macaca radiata) usually involved the subordinate female of a grooming dyad retreating at the approach of a female dominant to both members of the dyad. In a few exceptional cases, however, the dominant member of the dyad retreated; simple non-cognitive hypotheses involving dyadic rank differences and agonistic relationships failed to explain this phenomenon. Instead, retreat by the dominant individual was positively correlated with the social attractiveness of her subordinate companion (as measured by the duration of grooming received by the latter from other females in the troop). This suggests that not only does an individual evaluate relationships among other females, but does so on the basis of the amount of grooming received by them. Similarly, the frequency of approaches received by any female was correlated with her social attractiveness when she was the dominant member of the dyad, but not when she was the subordinate. This indicated that approaching females might be aware of the relative dominance ranks of the two allogrooming individuals. In logistic regression analyses, the probability of any individual retreating was found to be influenced more by her knowledge of her rank difference with both the other interactants, rather than by their absolute ranks. Moreover, information about social attractiveness appeared to be used in terms of correlated dominance ranks. The nature of knowledge acquired by bonnet macaque females may thus be egotistical in that other individuals are evaluated relative to oneself, integrative in that information about all other interactants is used simultaneously, and hierarchical in the ability to preferentially use certain categories of knowledge for the storage of related information from other domains.

Abstract: REASONS FOR PERFORMING STUDY: Serious injuries to horses and riders in horse trials (HT) and three-day events (3DE) are usually associated with falls of horses, which invariably involve falls of the riders. Many potential causes for these falls have been discussed. OBJECTIVES: The aim of this case-control study was to investigate the risk factors for horse falls on the cross-country phase of horse trials and three-day events. METHODS: Using retrospective data, significant risk factors identified with unvariable analysis (P value <0.2) were entered into a multivariable logistic regression model. Significant risk factors (P value <0.05) were included in the final model. RESULTS: It was revealed that a number of course, obstacle and rider variables were significantly and independently associated with the risk of falling. Falling was associated with obstacles sited downhill (Odds ratio [OR] 8.41) and with obstacles with ditches in front (OR = 5.77). CONCLUSIONS: The relationship between course variables and the risk of falling was characterised and showed a significantly increased risk with increasing numbers of jumps on the course and for jumping efforts later in the course. In contrast, after allowing for the total number of obstacles on the course, an increase in the total number of jumping efforts appeared to have a protective effect. A later cross-country start time was associated with a decreased risk of a horse fall. Amateur event riders were approximately 20 times more likely to fall than professional riders. POTENTIAL CLINICAL RELEVANCE: This study has identified a number of risk factors associated with horse falls and highlights areas that can be altered to improve safety in cross-country competitions.

Abstract: Among mammals, the members of some Orders have relatively large brains. Alternative explanations for this have emphasized either social or ecological selection pressures favouring greater information-processing capacities, including large group size, greater foraging efficiency, higher innovation rates, better invasion success and complex problem solving. However, the focal taxa for these analyses (primates, carnivores and birds) often show both varied ecological competence and social complexity. Here, we focus on the specific relationship between social complexity and brain size in ungulates, a group with relatively simple patterns of resource use, but extremely varied social behaviours. The statistical approach we used, phylogenetic generalized least squares, showed that relative brain size was independently associated with sociality and social complexity as well as with habitat use, while relative neocortex size is associated with social but not ecological factors. A simple index of sociality was a better predictor of both total brain and neocortex size than group size, which may indicate that the cognitive demands of sociality depend on the nature of social relationships as well as the total number of individuals in a group.

Abstract: Food-storing birds, black-capped chickadees (Poecile atricapilla), and nonstoring birds, dark-eyed juncos (Junco hyemalis), matched color or location on a touch screen. Both species showed a divided attention effect for color but not for location (Experiment 1). Chickadees performed better on location than on color with retention intervals up to 40 s, but juncos did not (Experiment 2). Increasing sample-distractor distance improved performance similarly in both species. Multidimensional scaling revealed that both use a Euclidean metric of spatial similarity (Experiment 3). When choosing between the location and color of a remembered item, food storers choose location more than do nonstorers. These results explain this effect by differences in memory for location relative to color, not division of attention or spatial discrimination ability.

Abstract: Pigeons were trained on operant schedules simulating successive encounters with prey items. When items were encountered on variable-interval schedules, birds were more likely to accept a poor item (long delay to food) the longer they had just searched, as if they were averaging prey density over a short memory window (Experiment 1). Responding as if the immediate future would be like the immediate past was reversed when a short search predicted a long search next time (Experiment 2). Experience with different degrees of environmental predictability appeared to change the length of the memory window (Experiment 3). The results may reflect linear waiting (Higa, Wynne, & Staddon, 1991), but they differ in some respects. The findings have implications for possible mechanisms of adjusting behavior to current reinforcement conditions.