Executive functions (EFs) are a set of cognitive operations, including working memory, inhibitory control and attention shifting, that underpin accurate, flexible and coordinated behaviour in many problem-solving contexts. While it seems likely that humans surpass nonhuman animals in EFs, previous research into the evolutionary origins of EFs is limited and lacks systematic comparisons of EFs in human and nonhuman animals. In this thesis, I aimed to overcome these limitations by developing a test battery to study EFs in our closest primate relative, the chimpanzee. Using an individual differences approach, I investigated the performance of 19 chimpanzees on several EF tasks and extracted two factors in an exploratory factor analysis accounting for 70.9 % of the variability. The two measures of working memory loaded onto one factor, suggesting that a common cognitive process underlay performance on both tasks. This factor could be clearly differentiated from a well-established measure of attention shifting, loading onto a second factor. In addition, the measures of inhibitory control did not contribute to a unique factor. Intriguingly, the emerging structure of separable EF processes, paralleled the EF structure suggested for human adults (Miyake et al, 2012). The subsequent comparison of a sub-sample of chimpanzees (n = 12; excluding aged individuals), pre-schoolers (n = 36) and undergraduates (n = 16) on two selected EF tests revealed impressive EF capacities of chimpanzees. Chimpanzees could deal with interference in working memory at levels comparable to four and five year-olds. Additionally, the ability of chimpanzees to shift attention was not significantly different from four year-olds; however, five- year-olds outperformed their primate relatives. My work suggests that important aspects of EFs are shared between humans and chimpanzees; while performance differences in EFs emerge late in human ontogeny. The implications of my results for theories on human cognitive evolution are discussed.

While the gestural communication of apes is widely recognised as intentional and flexible, their vocal communication still remains considered as mostly genetically determined and emotionally bound. Trying to limit the direct projections of linguistic concepts, that are far from holding a unified view on what constitute human language, this thesis presents a detailed description of the pant-grunt vocalisation usage and development in the chimpanzees (Pan troglodytes schweinfurthii) of the Budongo forest, Uganda. Pant-grunts are one of the most social vocalisations of the chimpanzee vocal repertoire and are always given from a subordinate individual to a dominant. The question of how such a signal is used and develops is critical for our understanding of chimpanzee social and vocal complexity in an ontogenetical and phylogenetical perpective. Results suggest that pant-grunt vocalisations can be used in a flexible way, both in their form and usage within a social group. More specifically, chimpanzees seemed to take into account the number and identity of surrounding individuals before producing these vocalisations. At the acoustic level, pant-grunts seem to be very variable vocalisations that corresponded to different social situations commonly encountered. Grunts are one of the first vocalisations produced by babies but they are not first produced in social contexts. Although some modifications of the social grunts form and usage could not entirely be attributed to maturation only, the role of the mother seemed to be restricted. Her direct influence was perhaps more visible in the rhythmic patterns of chorusing events. Taken together, this thesis suggests that chimpanzee vocalisations are more flexible in their usage, production and acquisition than previously thought and might therefore be more similar to gestural communication.

Finding food in tropical forests poses a potentially major problem for chimpanzees, whose ranging is thought primarily to be directed at locating suitable food resources: (1) chimpanzees are frugivorous, large bodied and live in large home ranges; (2) they lack specialised sensory or locomotor abilities, and terrestrial travel is known to be costly; but (3) fruits are randomly distributed in space and time. Evidence from studies of captive individuals suggests chimpanzees are capable of remembering the locations of out of sight resources and can compute least distance routes to these resources, but whether this ability translates to the natural foraging behaviour of wild chimpanzees has never been investigated. My observational study was designed to assess how the chimpanzees (Pan troglodytes schweinfurthii) of Budongo Forest, Uganda, locate these patchy resources. I mapped the routes of 14 focal individuals over a 12-month period. I considered how these foraging routes were structured by breaking the path into segments of travel between resources. Consecutive segments of travel between resources were found not to be independent, but assembled into "super-segments" that take in a number of resources along one trajectory. These super-segments are not necessarily directed towards feeding resources, however: travel is not always food directed. Comparisons of actual chimpanzee routes with randomly generated simulations suggest most individuals do not attempt to minimise their travel distances. There is evidence to suggest energetically stressed individuals can remember the locations of recently visited food resources and return to these patches in order to minimise travel distances when necessary, but overall, food is not difficult to find for this community of chimpanzees. I propose this is because males defend a territory with super-abundant food resources, meaning availability is not a limiting factor of foraging. Male chimpanzees can be characterised as convenience feeders, taking food whilst satisfying other, social needs.

The increasing rate of human population growth has expanded the human-primate interface, with more conversion of natural primate habitat to agricultural land. Elevated levels of crop-raiding by primates are a by-product of natural resources becoming less available, and the nutritional riches of agricultural production becoming increasingly known to the primates. It was the aim of this thesis to focus on the Bossou chimpanzees’ (Pan troglodytes verus) perspective of their habitat in the Republic of Guinea, West Africa, the risks and opportunities presented by a human-dominated landscape, and to detail their day-to-day coexistence with humans. I combined a variety of data collection techniques, from focal, scan and ad libitum behavioural sampling of the chimpanzees’ daily activities, to broad ecological and habitat surveys. The chimpanzees rely on cultivated foods, and thus are forced to respond to humans. However, significant variation in the importance of various cultivars in the chimpanzees’ diet exists; certain cultivars are mostly fallback foods, while others are preferred food items and taken according to their availability in orchards and fields. The usage patterns of wild and cultivated foods by the chimpanzees of Bossou are thus inextricably connected. Whilst engaged in crop-raiding the chimpanzees exhibit several behavioural adaptations, namely a decrease in vocalisation levels, and increases in the transportation of food and specific vigilance behaviour. Adult males and adult male-only parties crop-raid more than other age- and sex-classes/compositions, and are more likely to take risks by raiding in exposed environments with increased risk of human confrontation. The use of human cultivars also affects the socio-sexual behaviour of the chimpanzees: chimpanzees appear to share the fruits of their risky labours (crop-raiding) as a food-for-sex strategy, which allow adult males to advertise prowess and enhance affiliative relationships with reproductively valuable females (Hockings et al., in prep). In addition, behavioural adaptations to other anthropogenic high-risk situations such as road-crossing were found, with the chimpanzees exhibiting impressive levels of socio-spatial flexibility and cooperation (Hockings et al., 2006). The chimpanzees’ level of anxiety (as measured by rough self-directed scratching) increases when dealing with some of the challenges posed by their physical and social environment. The chimpanzees of Bossou have been forced to adapt ecologically and behaviourally to the various costs and benefits of living in a human-dominated environment.

The chimpanzee (Pan troglodytes, Pongidae) among all other living species, is our closest relation, with whom we last shared a common ancestor less than five million years ago. These African apes make and use a rich and varied kit of tools. Of the primates, and even of the other Great Apes, they are the only consistent and habitual tool-users. Chimpanzees meet the criteria of working definitions of culture as originally devised for human beings in socio-cultural anthropology. They show sex differences in using tools to obtain and to process a variety of plant and animal foods. The technological gap between chimpanzees and human societies living by foraging (hunter-gatherers) is surprisingly narrow, at least for food-getting. Different communities of chimpanzees have different tool-kits, and not all of this regional and local variation can be explained by the varied physical and biotic environments in which they live. Some differences are likely customs based on non-functionally derived and symbolically encoded traditions. Chimpanzees serve as heuristic, referential models for the reconstruction of cultural evolution in apes and humans from an ancestral hominoid. However, chimpanzees are not humans, and key differences exist between them, though many of these apparent contrasts remain to be explored empirically and theoretically.

I tested two pairs of captive chimpanzees (Pan troglodytes) in the informed forager paradigm: a subordinate saw the location of hidden bait, and then searched with a naïve dominant. This paradigm has tested what subjects know about others' states of knowledge, but my focus was to determine how subjects used different movement types and different gaze types to modify their competitive tactics. In particular, I investigated whether chimpanzees follow opponents' gaze to gain information. Learning more about how primates use visual information to predict others' behaviour can shed light on the continuing debate over to what degree apes possess theory of mind capacities. Previous published studies in this paradigm included narratives of ignorant competitors exploiting informed subjects by following their movement and gaze, and informed subjects avoided this exploitation by walking away from hidden food. The subordinate's behaviour can be considered tactical deception, which is a good place to seek strong evidence of second-order intentionality. Analyses with descriptive statistics, however, fail to capture the complexity of these interactions, which range from single decision-making points to larger patterns of following and misleading. I introduced a novel method of statistical analysis, cross correlations, that enabled me to examine behavioural patterns quantitatively that previous authors have only been able to describe in narrative form. Though previous studies on chimpanzees' understanding of gaze found that they were unable to use (human-given) gaze cues to locate hidden food, the subjects I tested followed their conspecific opponent's gaze, and used information gained from the gaze interaction to modify their own movement towards the hidden bait. Dominants adjusted their physical following of the subordinates as the interaction progressed, which reflected their changed states of knowledge. Subordinates used their movement and gaze differentially to manipulate dominants' behaviour, by withholding information and by recruiting towards a less-preferred bait.

Cumulative culture is rare, if not altogether absent in non-human species. At the foundation of cumulative learning is the ability to flexibly modify, relinquish or build upon prior behaviours to make them more productive or efficient. Within the primate literature, a failure to optimise solutions in this way is often proposed to derive from low-fidelity copying of witnessed behaviours, sub-optimal social learning heuristics, or a lack of relevant socio-cognitive adaptations. However, humans can also be markedly inflexible in their behaviours, perseverating with, or becoming fixated on outdated or inappropriate responses. Humans show differential patterns of flexibility as a function of cognitive load, exhibiting difficulties with inhibiting suboptimal behaviours when there are high demands on working memory. Here I present a series of studies on captive chimpanzees which show that not only is inhibitory control compromised in chimpanzees, but indicate ape behavioural conservatism may be underlain by similar constraints as in humans; chimpanzees show relatively little conservatism when behavioural optimisation involves the inhibition of a well-established but simple solution, or the addition of a simple modification to a well-established but complex solution. In contrast, when behavioural optimisation involves the inhibition of a well-established but complex solution, and especially when the alternative solution is also complex, chimpanzees show evidence of behavioural conservatism. I propose that conservatism is linked to behavioural complexity, potentially mediated by cognitive resource availability, and may be an important factor in the evolution of cumulative culture.

Zoological institutions emphasise the importance of excelling in the areas of animal welfare, conservation, education, and research, not only to better the lives of the animals under their care, but to also influence the general population in the pursuit to conserve the natural world. As a result, zoo life is anything but simple. This research project monitored the lives of a captive group of chimpanzees over a two-and-a-half-year period, during which time we explored four research topics while assessing the development of a cognitive research programme and chimpanzee (Pan troglodytes) introductions in a zoo: welfare, cognition, public engagement with science, and animal management. The project’s use of touchscreen technology and on-exhibit research was the first of its kind for the Royal Zoological Society of Scotland’s Edinburgh Zoo. As a result, the researchers placed a great deal of importance not only on assessing the welfare of the chimpanzees throughout training and testing phases, but also assessing the public’s perception of cognitive research being conducted through an internationally broadcast documentary about the project. In the short duration of the project, these research naïve chimpanzees did not fully grasp the concept of video selection in our free-choice activity, but overall, the introduction of a cognitive research programme did not compromise welfare, and the chimpanzees’ repeated interest suggests that chimpanzees found the research to be reinforcing. Partly funded by the BBC, the Chimpcam Project was shown in the UK (broadcast January 2010) and in a variety of other countries, including the United States and Canada (on Animal Planet in 2011). The broadcast allowed us to gather information over the internet on the wider public’s perception of conducting research with great apes in zoos, to complement data collected on visitors to the exhibit itself. Our assessment of the documentary’s impact on public perception showed that it had a positive influence on perceptions of zoo research, scientists, welfare, and the importance of choice for animals. During this research project, a new group of chimpanzees arrived in Edinburgh as part of the international breeding programme for western chimpanzees (Pan troglodytes verus). As the zoo’s focus switched to helping the two chimpanzee groups merge into one, we took the opportunity to apply psychological research to this context, namely the use of video as a research tool and the recognition of the importance of individual differences in response to challenge. The project maintained the cognition and welfare focus by using video introductions (allowing the chimpanzees to watch video footage of the individuals they were about to meet and track the formation of other sub-groups). In addition, personality ratings and chimpanzee behaviour during the visual access period (an animal management technique used prior to physical introductions where the groups could see each other without physical contact) were collected to examine the efficacy of these measures in guiding introductions in order to reduce risk. Personality ratings and behaviours observed during the video introductions could predict the chimpanzees’ behaviour during the physical introductions, however, the visual access period had no predictive power. The welfare implications of the introduction process were also assessed and suggested that: the choice of location (i.e. options of where to be) was more important than the total amount of available space; having individuals removed from your group was more stressful than having individuals added; self-directed behaviour (SDB) performance was context-specific where rubbing significantly increased during periods of uncertainty that were not necessarily negatively valenced; regurgitation and reingestion (R/R) decreased over time; and both in-group members and those of high ranks spent more time grooming others. Overall our data indicate that the chimpanzees coped well with both cognitive challenges and social upheaval during introductions. Despite being regularly studied in captivity and in the wild, chimpanzees have a great deal more to teach us about their world. In order to provide the best welfare for the chimpanzees in our care, we need to understand how research and management practices affect their lives and how the public interpret what we do as researchers. By understanding these aspects of their world, we can better serve those in captivity and influence public opinion on the importance of conserving those in the wild.