Abstract: Theoretical models have demonstrated the possibility of stable cost-free signalling of need between relatives. The stability of these cost-free equilibria depends on the indirect fitness cost of cheating and deceiving a donor into giving away resources. We show that this stability is highly sensitive to the distribution of need among signallers and receivers. In particular, cost-free signalling is likely to prove stable only if there is very large variation in need (such that the least-needy individuals stand to gain much less than the most-needy individuals from additional resources). We discuss whether these conditions are likely to be found in altricial avian breeding systems--the most intensively studied instance of signalling of need between relatives. We suggest that cost-free signalling is more likely to prove stable and will provide parents with more information during the earlier phases of chick growth, when parents can more easily meet the demands of a brood (and chicks are more likely to reach satiation). Later, informative yet cost-free signalling is unlikely to persist.

Abstract: Social group size has been shown to correlate with neocortex size in primates. Here we use comparative analyses to show that social group size is independently correlated with the size of non-V1 neocortical areas, but not with other more proximate components of the visual system or with brain systems associated with emotional cueing (e.g. the amygdala). We argue that visual brain components serve as a social information 'input device' for socio-visual stimuli such as facial expressions, bodily gestures and visual status markers, while the non-visual neocortex serves as a 'processing device' whereby these social cues are encoded, interpreted and associated with stored information. However, the second appears to have greater overall importance because the size of the V1 visual area appears to reach an asymptotic size beyond which visual acuity and pattern recognition may not improve significantly. This is especially true of the great ape clade (including humans), that is known to use more sophisticated social cognitive strategies.

Abstract: Domesticated animals are characterized by variability of breeds. There is a great diversity in body size and/or coat color between different breeds. However, there are few scientific researches about difference in cognition and behavior between breeds. Comparison of behavior between breeds may be useful for the study of genetics behind the diversity of cognition and behavior. In the present study, we investigated behavioral differences between horse breeds. We tested two different breeds which have different histories, thoroughbreds and creoles. Thoroughbreds are racing horses which have been exposed to strict selection toward racing performance for about 300 years. Creoles are descendents of horses which were brought to South America by Spanish people in 15th century and used by native cowboys for riding. We compared the behavior in a difficult situation by using an “unsolvable task”. The experimenter put a food reward into a transparent box and closed it firmly so that horses could not take the reward. We compared the referential behavior (gazing behavior toward the experimenter) between thoroughbreds and creoles. We analyzed referential behavior by using generalized linear models (GLM) and model selection by Akaike’s information criterion (AIC). There were no effect of breed in the frequency and the duration of the referential behavior. But the latency before looking at the experimenter tended to be shorter in thoroughbreds than in creoles. This result suggests that there may be breed differences in horses’ social cognition and behavior. However, the effect of sex was also seen. Furthermore, we could not exclude the environmental effect (e. g. feeding environments, trainings) in this study. So we cannot explain the variation in referential behavior by breed effect only. We need to replicate the result by controlling environmental effects.

Abstract: Despite considerable current interest in the evolution of intelligence, the intuitively appealing notion that brain volume and “intelligence” are linked remains untested. Here, we use ecologically relevant measures of cognitive ability, the reported incidence of behavioral innovation, social learning, and tool use, to show that brain size and cognitive capacity are indeed correlated. A comparative analysis of 533 instances of innovation, 445 observations of social learning, and 607 episodes of tool use established that social learning, innovation, and tool use frequencies are positively correlated with species' relative and absolute “executive” brain volumes, after controlling for phylogeny and research effort. Moreover, innovation and social learning frequencies covary across species, in conflict with the view that there is an evolutionary tradeoff between reliance on individual experience and social cues. These findings provide an empirical link between behavioral innovation, social learning capacities, and brain size in mammals. The ability to learn from others, invent new behaviors, and use tools may have played pivotal roles in primate brain evolution.