Differentiated responses to different human conditions by chimpanzees

Where to draw the line?

We often take people’s ability to understand and produce line drawings for granted. But where should we draw lines, and why? We address psychological principles that underlie efficient representations of complex information in line drawings. First, 58 participants with varying degree of artistic experience produced multiple drawings of a small set of scenes by tracing contours on a digital tablet. Second, 37 independent observers ranked the drawings by how representative they are of the original photograph. Matching contours between drawings of the same scene revealed that the most consistently drawn contours tend to be drawn earlier. We generated half-images with the most- versus least-consistently drawn contours and asked 25 observers categorize the quickly presented scenes. Observers performed significantly better for the most compared to the least consistent half-images. The most consistently drawn contours were more likely to depict occlusion boundaries, whereas the least consistently drawn contours frequently depicted surface normals.

A review of research in primate sanctuaries

While non-human primate studies have long been conducted in laboratories, and more recently at zoological parks, sanctuaries are increasingly considered a viable setting for research. Accredited sanctuaries in non-range countries house thousands of primates formerly used as subjects of medical research, trained performers or personal pets. In range countries, however, sanctuaries typically house orphaned primates confiscated from illegal poaching and the bushmeat and pet trafficking trades. Although the primary mission of these sanctuaries is to rescue and rehabilitate residents, many of these organizations are increasingly willing to participate in non-invasive research. Notably, from a scientific standpoint, most sanctuaries provide potential advantages over traditional settings, such as large, naturalistic physical and social environments which may result in more relevant models of primates' free-ranging wild counterparts than other captive settings. As a result, an impressive scope of research in the fields of primate behaviour, cognition, veterinary science, genetics and physiology have been studied in sanctuaries. In this review, we examine the range and form of research that has been conducted at accredited sanctuaries around the world. We also describe the potential challenges of sanctuary-based work and the considerations that external researchers may face when deciding to collaborate with primate sanctuaries on their research projects.

Social stimuli and social rewards in primate learning and cognition

Many studies have suggested that non-human primates have good individual recognition abilities, that social stimuli can serve as discriminative stimuli in learning tests and that visual access to social objects or events can be a reinforcer for operant behaviour. Intensified research efforts comparing the effectiveness of social and non-social stimuli and rewards across a range of learning and other cognitive tasks would help clarify the extent to which monkeys and apes might be specially predisposed to process information in the social domain. In addition to identity, social interactions and relationships constitute raw material to be mentally represented and processed. Some studies have addressed the individual and evolutionary origins of mechanisms underlying the ability to attribute mental states and intentions to others, for example by looking at the understanding of another's gaze, imitation and the development of tactical deception. The results of some of this research suggest that only some species might be capable of higher-order attribution. Further progress in the study of primate social cognition will require continuing refinement of methods and the development of new techniques to compare primates as behaviourists and mentalists.