Great ape cognition is structured by stable cognitive abilities and predicted by developmental conditions.

Great ape cognition is used as a reference point to specify the evolutionary origins of complex cognitive abilities, including in humans. This research often assumes that great ape cognition consists of cognitive abilities (traits) that account for stable differences between individuals, which change and develop in response to experience. Here, we test the validity of these assumptions by assessing repeatability of cognitive performance among captive great apes (Gorilla gorilla, Pongo abelii, Pan paniscus, Pan troglodytes) in five tasks covering a range of cognitive domains.

Are you as fooled as I am? Visual illusions in human (Homo) and nonhuman (Sapajus, Gorilla, Pan, Pongo) primate species.

It has been argued that humans' susceptibility to visual illusions does not simply reflect cognitive flaws but rather specific functional adaptations of our perceptual system. The data on cross-cultural differences in the perception of geometric illusions seemingly support this explanation. Little is known, however, about the developmental trajectories of such adaptations in humans, let alone a conclusive picture of the illusionary susceptibility in other primate species.

Old and New Approaches to Animal Cognition: There Is Not "One Cognition".

Using the comparative approach, researchers draw inferences about the evolution of cognition. Psychologists have postulated several hypotheses to explain why certain species are cognitively more flexible than others, and these hypotheses assume that certain cognitive skills are linked together to create a generally "smart" species. However, empirical findings suggest that several animal species are highly specialized, showing exceptional skills in single cognitive domains while performing poorly in others.

Establishing an infrastructure for collaboration in primate cognition research.

Inferring the evolutionary history of cognitive abilities requires large and diverse samples. However, such samples are often beyond the reach of individual researchers or institutions, and studies are often limited to small numbers of species. Consequently, methodological and site-specific-differences across studies can limit comparisons between species.

Chimpanzees use observed temporal directionality to learn novel causal relations.

We investigated whether chimpanzees use the temporal sequence of external events to determine causation. Seventeen chimpanzees (Pan troglodytes) witnessed a human experimenter press a button in two different conditions. When she pressed the "causal button" the delivery of juice and a sound immediately followed (cause-then-effect).

How prior experience and task presentation modulate innovation in 6-year-old-children.

Low innovation rates have been found with children until 6-8 years of age in tasks that required them to make a tool. Little is known about how prior experience and task presentation influence innovation rates. In the current study, we investigated these aspects in the floating peanut task (FPT), which required children to pour water into a vertical tube to retrieve a peanut.

Chimpanzees Consider Humans' Psychological States when Drawing Statistical Inferences.

Great apes have been shown to be intuitive statisticians: they can use proportional information within a population to make intuitive probability judgments about randomly drawn samples [1, J.E., J.

Causal reasoning versus associative learning: A useful dichotomy or a strawman battle in comparative psychology?

The debate about whether or not one could/should ascribe reasoning abilities to animals has deep historical roots and seems very up-to-date in the light of the immense body of new empirical data originating from various species and research paradigms. Associative learning (AL) seems to be a ubiquitous low-level contender for any cognitive interpretation of animal behavior, mostly because of the assumed mechanistic simplicity and phylogenetic prevalence. However, the implicit assumption that AL is simple and therefore the most parsimonious mechanism to describe seemingly complex behavior can and must be questioned on various grounds.

Making sense of (exceptional) causal relations. A cross-cultural and cross-linguistic study.

In order to make sense of the world, humans tend to see causation almost everywhere. Although most causal relations may seem straightforward, they are not always construed in the same way cross-culturally. In this study, we investigate concepts of "chance," "coincidence," or "randomness" that refer to assumed relations between intention, action, and outcome in situations, and we ask how people from different cultures make sense of such non-law-like connections.

Does presentation format influence visual size discrimination in tufted capuchin monkeys (Sapajus spp.)?

Most experimental paradigms to study visual cognition in humans and non-human species are based on discrimination tasks involving the choice between two or more visual stimuli. To this end, different types of stimuli and procedures for stimuli presentation are used, which highlights the necessity to compare data obtained with different methods. The present study assessed whether, and to what extent, capuchin monkeys' ability to solve a size discrimination problem is influenced by the type of procedure used to present the problem.

When maths trumps logic: probabilistic judgements in chimpanzees.

When searching for hidden food, do chimpanzees take into account both the number of hidden items and the number of potential hiding locations? We presented chimpanzees with two trays, each of them containing a different food/cup ratio and therefore a different likelihood of finding a baited cup among empty alternatives. Subjects' performance was directly influenced by the relative difference (probability ratio (PR)) between the two given probabilities. Interestingly, however, they did not appreciate the special value of a truly safe option (with P = 1.

Comparing the performances of apes (Gorilla gorilla, Pan troglodytes, Pongo pygmaeus) and human children (Homo sapiens) in the floating peanut task.

Recently, Mendes et al. [1] described the use of a liquid tool (water) in captive orangutans. Here, we tested chimpanzees and gorillas for the first time with the same "floating peanut task.

Chimpanzee problem-solving: contrasting the use of causal and arbitrary cues.

Humans are able to benefit from a causally structured problem-solving context rather than arbitrarily structured situations. In order to better understand nonhuman causal cognition, it is therefore important to isolate crucial factors that might differentiate between events that follow a purely spatial and temporal contingency and those that hold a "true" causal relationship. In the first of two experiments, chimpanzee subjects were required to detect a bottle containing juice from five opaque bottles of equal shape and size.

Discrete quantity judgments in the great apes (Pan paniscus, Pan troglodytes, Gorilla gorilla, Pongo pygmaeus): the effect of presenting whole sets versus item-by-item.

The authors examined quantity-based judgments for up to 10 items for simultaneous and sequential whole sets as well as for sequentially dropped items in chimpanzees (Pan troglodytes), gorillas (Gorilla gorilla), bonobos (Pan paniscus), and orangutans (Pongo pygmaeus). In Experiment 1, subjects had to choose the larger of 2 quantities presented in 2 separate dishes either simultaneously or 1 dish after the other. Representatives of all species were capable of selecting the larger of 2 quantities in both conditions, even when the quantities were large and the numerical distance between them was small.

Raising the level: orangutans use water as a tool.

We investigated the use of water as a tool by presenting five orangutans (Pongo abelii) with an out-of-reach peanut floating inside a vertical transparent tube. All orangutans collected water from a drinker and spat it inside the tube to get access to the peanut. Subjects required an average of three mouthfuls of water to get the peanut.

Spontaneous altruism by chimpanzees and young children.

People often act on behalf of others. They do so without immediate personal gain, at cost to themselves, and even toward unfamiliar individuals. Many researchers have claimed that such altruism emanates from a species-unique psychology not found in humans' closest living evolutionary relatives, such as the chimpanzee.