Abstract: In the past, equine color vision was tested with stimuli composed either of painted cards or photographic slides or through physiological testing using electroretinogram flicker photometry. Some studies produced similar results, but others did not, demonstrating that there was not yet a definitive answer regarding color vision in horses (Equus caballus). In this study, a pseudoisochromatic plate test--which is highly effective in testing color vision both in small children and in adult humans--was used for the first time on a nonhuman animal. Stimuli consisted of different colored dotted circles set against backgrounds of varying dots. The coloration of the circles corresponded to the visual capabilities of different types of color deficiencies (anomalous trichromacy and dichromacy). Four horses were tested on a 2-choice discrimination task. All horses successfully reached criterion for gray circles and demonstration circles. None of the horses were able to discriminate the protan-deutan plate or the individual protan or deutan plates. However, all were able to discriminate the tritan plate. The results suggest that horses are dichromats with color vision capabilities similar to those of humans with red-green color deficiencies.

Abstract: The claim that differences in brain size across primate species has mainly been driven by the demands of sociality (the “social brain” hypothesis) is now widely accepted. Some of the evidence to support this comes from the fact that species that live in large social groups have larger brains, and in particular larger neocortices. Lindenfors and colleagues (BMC Biology 5:20) add significantly to our appreciation of this process by showing that there are striking differences between the two sexes in the social mechanisms and brain units involved. Female sociality (which is more affiliative) is related most closely to neocortex volume, but male sociality (which is more competitive and combative) is more closely related to subcortical units (notably those associated with emotional responses). Thus different brain units have responded to different selection pressures.

Abstract: Definitions of what features constitute cultural behaviour, and hence define cultures are numerous. Many seem designed to describe those aspects of human behaviour which set us apart from other animals. A broad definition prescribing that the behaviour is: learned; learned socially; normative and collective is considered to apply to several species of great ape. In this paper, I review observations and experiments covering a suite of different behavioural characteristics displayed in members of the bowerbird family (Ptilonorhynchidae) and ask whether they fulfil these criteria. These include vocalisations, bower design, decoration use, bower orientation and display movements. Such a range of behaviours refutes the suggestion that these species are “one-trick ponies”-a criticism that is often levelled at claims for culture in non-primate species. I suggest that, despite a paucity of data in comparison with primate studies, it could be argued that bowerbirds may be considered to fulfil the same criteria on which we base our use of the term culture when applied to our close relatives, the great apes. If bowerbirds do have cultures, then their unusual natural history makes them a highly tractable system in which questions of social learning and culture can be tackled.

Abstract: Expertise acquisition may be a universal attribute of animals. In this study data on foraging efficiency, or expertise, was compared for four species: honeybees (Apis mellifera), oystercatchers (Haematopus ostralegus), chimpanzees (Pan troglodytes), and humans (Homo sapiens). Polynomial regression models were constructed to investigate the relationship between age and foraging efficiency. There was a similar expertise-acquisition function between age and foraging efficiency across species, best described by a quadratic equation. The peak of performance was reached, in all cases, before the average age of death but well after reaching physical maturity and the percentage of lifespan devoted to the skill was more than 10% of the species-typical lifespan.

Abstract: Recent evidence for different tool kits, proposed to be based upon culture-like transmission, have been observed across different chimpanzee communities across Western Africa. In light of these findings, the reported failures by seven captive juvenile chimpanzees tested with 27 tool use tasks (Povinelli 2000) seem enigmatic. Here we report successful performance by a group of nine captive, enculturated chimpanzees, and limited success by a group of six semi-enculturated chimpanzees, on two of the Povinelli tasks, the Flimsy Tool task, and the Hybrid Tool task. All chimpanzees were presented with a rake with a flimsy head and a second rake with a rigid head, either of which could be used to attempt to retrieve a food reward that was out of reach. The rigid rake was constructed such that it had the necessary functional features to permit successful retrieval, while the flimsy rake did not. Both chimpanzee groups in the present experiment selected the functional rigid tool correctly to use during the Flimsy Tool task. All animals were then presented with two “hybrid rakes” A and B, with one half of each rake head constructed from flimsy, non-functional fabric, and the other half of the head was made of wood. Food rewards were placed in front of the rigid side of Rake A and the flimsy side of Rake B. To be successful, the chimps needed to choose the rake that had the reward in front of the rigid side of the rake head. The fully enculturated animals were successful in selecting the functional rake, while the semi-enculturated subjects chose randomly between the two hybrid tools. Compared with findings from Povinelli, whose non-enculturated animals failed both tasks, our results demonstrate that chimpanzees reared under conditions of semi-enculturation could learn to discriminate correctly the necessary tool through trial-and-error during the Flimsy Tool task, but were unable to recognize the functional relationship necessary for retrieving the reward with the “hybrid” rake. In contrast, the enculturated chimpanzees were correct in their choices during both the Flimsy Tool and the Hybrid Tool tasks. These results provide the first empirical evidence for the differential effects of enculturation on subsequent tool use capacities in captive chimpanzees.