Alejandro Sánchez-Amaro

Max Planck Institute for Evolutionary Anthropology | EVA · Department of Comparative Cultural Psychology

The ultimatum game (UG) is widely used to investigate our sense of fairness, a key characteristic that differentiates us from our closest living relatives, bonobos and chimpanzees. Previous studies found that, in general, great apes behave as rational maximizers in the UG. Proposers tend to choose self-maximizing offers, while responders accept mos...

Social primates face conflicts of interest with other partners when their individual and collective interests collide. Despite living in small, primarily bonded, groups compared to other social primates, gibbons are not exempt from these conflicts in their everyday lives. In the current task, we asked whether dyads of gibbons would solve a conflict...

Social primates constantly face situations in which their preferences collide and they need to engineer strategies to overcome conflicts of interest. Studies with chimpanzees, Pan troglodytes, have found that they use competitive strategies to overcome social dilemmas, maximizing their own benefits while minimizing the loss of rewards. However, lit...

Animals need to adjust their decision-making strategies to the ecological challenges of their environment. Variation in ecological unpredictability and harshness thus seem to affect their decisions in the wild. In our study, we combine methods from human life history theory and previous comparative work with chimpanzees to investigate whether curre...

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 s...

Humans are perhaps the most curious animals on earth, but to what extent our innate motivations for discovering new information are shared with our closest relatives remain poorly understood. To shed light on this question, we presented great apes with two experimental paradigms in which they had to initially choose between an empty opaque cup and...

Partner choice promotes competition among individuals to be selected as a cooperative partner, a phenomenon referred to as competitive altruism. Our study explores chimpanzees' competitive altruism in a triadic Ultimatum Game where two proposers can send offers to a responder who can only accept one offer. Chimpanzees engaged in competitive altruis...

Short-term memory is implicated in a range of cognitive abilities and is critical for understanding primate cognitive evolution. To investigate the effects of phylogeny, ecology and sociality on short-term memory, we tested the largest and most diverse primate sample to date (421 non-human primates across 41 species) in an experimental delayed-resp...

Social primates face conflicts of interest with other partners when their individual and collective interests collide. Despite living in small, primarily dyadic, groups compared to other social primates, gibbons are not exempt from these conflicts in their everyday lives. In the current task, we asked whether pairs of gibbons would solve a conflict...

Individuals with an advantageous position during a negotiation possess leverage over their partners. Several studies with adults have investigated how leverage can influence the coordination strategies of individuals when conflicts of interest arise. In this study, we explored how pairs of 7-year-old children solved a coordination game (based on th...

How much nonhuman animals understand about seeing has been the focus of comparative cognition research for decades. Many social primates (and other species) are sensitive to cues about what others can and cannot see. Whether this sensitivity evolved in primates through shared descent or convergent evolution remains unclear. The current study tested...

The field of primate cognition studies how primates, including humans, perceive, process, store, retrieve, and use information to guide decision making and other behavior. Much of this research is motivated by a desire to understand how these abilities evolved. Large and diverse samples from a wide range of species are vital to achieving this goal....

The decoy effect is a violation of rationality that occurs when the relative preference between two target options changes with the addition of a third option, called the decoy, that is no better than the target options but worse than one of the options on one attribute. The presence of the decoy increases the chance that the option that dominates...

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 s...

The relationship between language and thought is controversial. One hypothesis is that language fosters habits of processing information that are retained even in non-linguistic domains. In left-branching (LB) languages, modifiers usually precede the head, and real-time sentence comprehension may more heavily rely on retaining initial information i...

The field of primate cognition studies how primates, including humans, perceive, process, store, retrieve, and use information to guide decision making and other behavior. Much of this research is motivated by a desire to understand how these abilities evolved. Large and diverse samples from a wide range of species are vital to achieving this goal....

Supporting information. (DOCX)

Social primates can influence others through the control of resources. For instance, dominant male chimpanzees might allow subordinates access to mate with females in exchange for social support. However, little is known about how chimpanzees strategically use a position of leverage to maximize their own benefits. We address this question by presen...

Cooperation often comes with the temptation to defect and benefit at the cost of others. This tension between cooperation and defection is best captured in social dilemmas like the Prisoner’s Dilemma. Adult humans have specific strategies to maintain cooperation during Prisoner’s Dilemma interactions. Yet, little is known about the ontogenetic and...

The sunk cost effect is a human propensity to pursue a course of action and resource investment without considering its prospective results (Arkes & Blumer, 1985), which has also been reported in rodents and birds using various operant procedures. No studies to date, however, have tested this effect without extensive training. We used a manipulatio...

Social animals need to coordinate with others to reap the benefits of groupliving even when individuals’ interests are misaligned. We compare how chimpanzees, bonobos and children coordinate their actions with a conspecific in a Snowdrift game, which provides a model for understanding how organisms coordinate and make decisions under conflict. In s...

Correspondence: A. Sánchez-Amaro, Max Planck Institute for Evolutionary Anthropology, Developmental and Comparative Psychology, Deutscher Platz 6, 04103, Leipzig, Germany.

Chimpanzees must be able to coordinate with others even when conflicts of interest are present. The “Snowdrift-Game” provides a model to understand how organisms coordinate and make decisions under conflict situations. By investigating whether and how chimpanzees solve this dilemma we can gain insight into the mechanisms of cooperation. Moreover, b...

The snowdrift game is a model for studying social coordination in the context of competing interests. We presented pairs of chimpanzees with a situation in which they could either pull a weighted tray together or pull alone to obtain food. Ultimately chimpanzees should coordinate their actions because if no one pulled, they would both lose the rewa...

Chimpanzees must be able to coordinate with others even when conflicts of interest are present. The “Snowdrift-Game” provides a model to understand how organisms coordinate and make decisions under conflict situations. By investigating whether and how chimpanzees solve this dilemma we can gain insight into the mechanisms of cooperation. Moreover, b...

Biological Market Theory (BMT) has provided an elegant framework to study how commodities are exchanged among individuals. In primates, BMT predicts that individuals exchange grooming with other commodities based on the law of supply and demand. However, BMT still suffers some theoretical and methodological limitations. Our aim in this paper is to...

We investigated how apes allocated their choices between 2 food options that varied in terms of their quantity and quality. Experiment 1 tested whether subjects preferred an AB option over an A option, where the A item is preferred to the B item (e.g., apple + carrot vs. apple). Additionally, we tested whether the length of the intertrial interval...

Little evidence of calculated reciprocity has been found in non-human primates so far. In this study, we used a simple experimental set-up to test whether partners pulled a sliding table to altruistically provide food to each other in short-term interactions. We tested 46 dyads of chimpanzees, bonobos, gorillas, orangutans, brown capuchin monkeys a...