Evolutionary variation in cognition

Imagine a choice between two potential jobs: a position that is stable but intellectually mundane, or one that is more exciting but offers only short contract with some chance of renewal. These kinds of decisions can be agonizing because they involve uncertainty. While the first job option is a known quantity, the second job offers the possibility of being more fulfilling, but also the possibility of being let go in the near future. This uncertainty means that it is not possible to know the exact consequences of the decision in advance, making it difficult to judge the best course of action. Many important decisions involve this same sort of uncertainty—such as whether to invest in a new business, commit to a partner, or pursue a medical treatment. Yet uncertainty is not something only humans experience: it is pervasive in the natural world, and all animals must sometimes make decisions without complete information about the consequences of their actions. Consequently, illuminating how decision-makers respond to uncertainty is a problem of interest across both the social and biological sciences. This review will integrate theory from economics, psychology, and biology in order to understand the psychological mechanisms that animals use to make decisions under uncertainty, as well as what biological function these mechanisms might have. I further argue that comparative research is a powerful tool for understanding the nature of economic decision-making. Discovering that a particular decision-making pattern is widely shared across humans and other species—or conversely, unique to humans alone—can provide important insights about the types of experiences that engender these psychological processes.

Human cognition is permeated by self-control: the ability to engage in complex, goal-oriented behaviors rather than just react to the moment at hand. This chapter examines the evolutionary roots of these abilities by comparing the psychological capacities of humans and other primates. In fact, there is marked variation in how different primate species control their motoric responses to inhibit prepotent but ineffectual actions, engage in strategic decision-making to determine the best course of action, and learn and update their responses when contingencies change. Understanding how and why this variation emerged can shed light on the origins of human cognition.

Money and biological rewards differ in many ways. Yet studies of human decision-making typically involve money, whereas nonhuman studies involve food. We therefore examined how context shifts human risk preferences to illuminate the evolution of decision-making. First, we assessed peoples’ risk preferences across food, prizes, and money in a task where individuals received real rewards and learned about payoffs through experience. We found that people were relatively more risk-seeking for both food and prizes compared to money—indicating that people may treat abstract reward markers differently from concrete rewards. Second, we compared human risk preferences for food with the performance of our closest phylogenetic relatives, chimpanzees (Pan troglodytes) and bonobos (Pan paniscus), in order to illuminate the evolutionary origins of human decision-making strategies. In fact, human and chimpanzees were both relatively more risk-seeking compared to bonobos. Finally, we investigated why people respond differently to money versus concrete rewards when making decisions. We found that people were more risk-prone when making decisions about money that was constrained as a store of value, compared to money that could be freely exchanged. This shows that people are sensitive to money’s usefulness as a store of value that can be used to acquire other types of rewards. Our results indicate that humans exhibit different preferences when making risky decisions about money versus food, an important consideration for comparative research. Furthermore, different psychological processes may underpin decisions about abstract rewards compared to concrete rewards.

Humans exhibit framing effects when making choices, appraising decisions involving losses differently from those involving gains. To directly test for the evolutionary origin of this bias, we examined decision-making in humans’ closest living relatives: bonobos (Pan paniscus) and chimpanzees (Pan troglodytes). We presented the largest sample of non-humans to date (n = 40) with a simple task requiring minimal experience. Apes made choices between a ‘framed’ option that provided preferred food, and an alternative option that provided a constant amount of intermediately preferred food. In the gain condition, apes experienced a positive ‘gain’ event in which the framed option was initially presented as one piece of food but sometimes was augmented to two. In the loss condition, apes experienced a negative ‘loss’ event in which they initially saw two pieces but sometimes received only one. Both conditions provided equal pay-offs, but apes chose the framed option more often in the positive ‘gain’ frame. Moreover, male apes were more susceptible to framing than were females. These results suggest that some human economic biases are shared through common descent with other apes and highlight the importance of comparative work in understanding the origins of individual differences in human choice.

Humans exhibit a suite of biases when making economic decisions. We review recent research on the origins of human decision making by examining whether similar choice biases are seen in nonhuman primates, our closest phylogenetic relatives. We propose that comparative studies can provide insight into four major questions about the nature of human choice biases that cannot be addressed by studies of our species alone. First, research with other primates can address the evolution of human choice biases and identify shared versus human-unique tendencies in decision making. Second, primate studies can constrain hypotheses about the psychological mechanisms underlying such biases. Third, comparisons of closely related species can identify when distinct mechanisms underlie related biases by examining evolutionary dissociations in choice strategies. Finally, comparative work can provide insight into the biological rationality of economically irrational preferences.

The interface between cognition, emotion, and motivation is thought to be of central importance in understanding complex cognitive functions such as decision-making and executive control in humans. Although nonhuman apes have complex repertoires of emotional expression, little is known about the role of affective processes in ape decision-making. To illuminate the evolutionary origins of human-like patterns of choice, we investigated decision-making in humans’ closest phylogenetic relatives, chimpanzees (Pan troglodytes) and bonobos (Pan paniscus). In two studies, we examined these species’ temporal and risk preferences, and assessed whether apes show emotional and motivational responses in decision making contexts. We find that (1) chimpanzees are more patient and more risk-prone than are bonobos, (2) both species exhibit affective and motivational responses following the outcomes of their decisions, and (3) some emotional and motivational responses map onto species-level and individual-differences in decision-making. These results indicate that apes do exhibit emotional responses to decision-making, like humans. We explore the hypothesis that affective and motivational biases may underlie the psychological mechanisms supporting value-based preferences in these species.

Now more than ever animal studies have the potential to test hypotheses regarding how cognition evolves. Comparative psychologists have developed new techniques to probe the cognitive mechanisms underlying animal behavior, and they have become increasingly skillful at adapting methodologies to test multiple species. Meanwhile, evolutionary biologists have generated quantitative approaches to investigate the phylogenetic distribution and function of phenotypic traits, including cognition. In particular, phylogenetic methods can quantitatively (1) test whether specific cognitive abilities are correlated with life history (e.g., lifespan), morphology (e.g., brain size), or socio-ecological variables (e.g., social system), (2) measure how strongly phylogenetic relatedness predicts the distribution of cognitive skills across species, and (3) estimate the ancestral state of a given cognitive trait using measures of cognitive performance from extant species. Phylogenetic methods can also be used to guide the selection of species comparisons that offer the strongest tests of a priori predictions of cognitive evolutionary hypotheses (i.e., phylogenetic targeting). Here, we explain how an integration of comparative psychology and evolutionary biology will answer a host of questions regarding the phylogenetic distribution and history of cognitive traits, as well as the evolutionary processes that drove their evolution.

Although recent research has investigated animal decision-making under risk, little is known about how animals choose under conditions of ambiguity when they lack information about the available alternatives. Many models of choice behaviour assume that ambiguity does not impact decision-makers, but studies of humans suggest that people tend to be more averse to choosing ambiguous options than risky options with known probabilities. To illuminate the evolutionary roots of human economic behaviour, we examined whether our closest living relatives, chimpanzees (Pan troglodytes) and bonobos (Pan paniscus), share this bias against ambiguity. Apes chose between a certain option that reliably provided an intermediately preferred food type, and a variable option that could vary in the probability that it provided a highly preferred food type. To examine the impact of ambiguity on ape decision-making, we interspersed trials in which chimpanzees and bonobos had no knowledge about the probabilities. Both species avoided the ambiguous option compared with their choices for a risky option, indicating that ambiguity aversion is shared by humans, bonobos and chimpanzees.