Abstract: The manipulative actions of mountain gorillas Gorilla g. beringei were examined in the context of foraging on hard-to-process plant foods in the field, in particular those used in tackling thistle Carduus nyassanus. A repertoire of 72 functionally distinct manipulative actions was recorded. Many of these actions were used in several variants of grip, finger(s) and movement path, both by different individuals and by the same individual at different times. The repertoire appears somewhat greater than that observed in comparable studies of monkeys, but a far more striking difference is found in the use of differentiated actions in concert. Mountain gorillas routinely and frequently deal with problems that involve: (1) bimanual role differentiation, with the two hands taking different roles but synchronized in time and space, and (2) digit role differentiation, with independent control of parts of the same hand used for separate purposes at the same time. The independent control that allows these abilities, so crucial to human manual constructional ability, is apparently general in African great apes. Role differentiation, between and within the hand, is evidently a primitive characteristic in the human arsenal of skills.

Abstract: Imitation can be defined as the copying of behavior. To a biologist, interest in imitation is focused on its adaptive value for the survival of the organism, but to a psychologist, the mechanisms responsible for imitation are the most interesting. For psychologists, the most important cases of imitation are those that involve demonstrated behavior that the imitator cannot see when it performs the behavior (e.g., scratching one's head). Such examples of imitation are sometimes referred to as opaque imitation because they are difficult to account for without positing cognitive mechanisms, such as perspective taking, that most animals have not been acknowledged to have. The present review first identifies various forms of social influence and social learning that do not qualify as opaque imitation, including species-typical mechanisms (e.g., mimicry and contagion), motivational mechanisms (e.g., social facilitation, incentive motivation, transfer of fear), attentional mechanisms (e.g., local enhancement, stimulus enhancement), imprinting, following, observational conditioning, and learning how the environment works (affordance learning). It then presents evidence for different forms of opaque imitation in animals, and identifies characteristics of human imitation that have been proposed to distinguish it from animal imitation. Finally, it examines the role played in opaque imitation by demonstrator reinforcement and observer motivation. Although accounts of imitation have been proposed that vary in their level of analysis from neural to cognitive, at present no theory of imitation appears to be adequate to account for the varied results that have been found.

Abstract: Abstract  Encounters between groups of wild chacma baboons (Papio ursinus) can be viewed as a natural experiment to investigate the nature of these primates mental representations of large-scale space. During a 16-month field study in a high population density habitat we recorded the foraging routes and the most important resources of a group of 25 individuals. Also, we estimated the locations of additional baboon groups relative to the study group. Routes were less linear, travel speed was higher, and inter-resource distances were larger when other groups were present within 500 m of the focal group; thus, the study group avoided others by taking detours. We predicted that evasive manoeuvres would be characteristic of different possible orientation mechanisms, and compared them with our observations. We analysed 34 evasive manoeuvres in detail. In an area that lacked prominent landmarks, detours were small; larger detours occurred when resources were directly visible, or in the vicinity of a hill offering conspicuous landmarks. In areas without prominent landmarks, detours were along familiar routes and waiting bouts of up to 60 min occurred; on one occasion the study group aborted their entire day`s journey. We discuss these findings in the light of time and energy costs and suggest that the baboons lack the ability to compute Euclidean relations among locations, but use network maps to find their way to out-of-sight locations.

Abstract: The ability to learn through imitation is thought to be the basis of cultural transmission and was long considered a distinctive characteristic of humans. There is now evidence that both mammals and birds are capable of imitation. However, nothing is known about these abilities in the third amniotic class--reptiles. Here, we use a bidirectional control procedure to show that a reptile species, the bearded dragon (Pogona vitticeps), is capable of social learning that cannot be explained by simple mechanisms such as local enhancement or goal emulation. Subjects in the experimental group opened a trap door to the side that had been demonstrated, while subjects in the ghost control group, who observed the door move without the intervention of a conspecific, were unsuccessful. This, together with differences in behaviour between experimental and control groups, provides compelling evidence that reptiles possess cognitive abilities that are comparable to those observed in mammals and birds and suggests that learning by imitation is likely to be based on ancient mechanisms.

Abstract: Abstract  Many wild primates occupy large home ranges and travel long distances each day. Navigating these ranges to find sufficient food presents a substantial cognitive challenge, but we are still far from understanding either how primates represent spatial information mentally or how they use this information to navigate under natural conditions. In the course of a long-term socioecological study, we investigated and compared the travel paths of sympatric spider monkeys (Ateles belzebuth) and woolly monkeys (Lagothrix poeppigii) in Amazonian Ecuador. During several field seasons spanning an 8-year period, we followed focal individuals or groups of both species continuously for periods of multiple days and mapped their travel paths in detail. We found that both primates typically traveled through their home ranges following repeatedly used paths, or “routes”. Many of these routes were common to both species and were stable across study years. Several important routes appeared to be associated with distinct topographic features (e.g., ridgetops), which may constitute easily recognized landmarks useful for spatial navigation. The majority of all location records for both species fell along or near identified routes, as did most of the trees used for fruit feeding. Our results provide strong support for the idea that both woolly and spider monkey use route-based mental maps similar to those proposed by Poucet (Psychol Rev 100:163-182, 1993). We suggest that rather than remembering the specific locations of thousands of individual feeding trees and their phenological schedules, spider and woolly monkeys could nonetheless forage efficiently by committing to memory a series of route segments that, when followed, bring them into contact with many potential feeding sources for monitoring or visitation. Furthermore, because swallowed and defecated seeds are deposited in greater frequency along routes, the repeated use of particular travel paths over generations could profoundly influence the structure and composition of tropical forests, raising the intriguing possibility that these and other primate frugivores are active participants in constructing their own ecological niches. Building upon the insights of Byrne (Q J Exp Psychol 31:147-154, 1979, Normality and pathology in cognitive functions. Academic, London, pp 239-264, 1982) and Milton (The foraging strategy of howler monkeys: a study in primate economics. Columbia University Press, New York, 1980, On the move: how and why animals travel in groups. University of Chicago Press, Chicago, pp 375-417, 2000), our results highlight the likely general importance of route-based travel in the memory and foraging strategies of nonhuman primates.