The Moral Brain: A Multidisciplinary Perspective

The Moral Brain

The Moral Brain

A Multidisciplinary Perspective

Edited by Jean Decety and Thalia Wheatley

The MIT Press

Cambridge, Massachusetts

London, England

© 2015 Massachusetts Institute of Technology

All rights reserved. No part of this book may be reproduced in any form by any electronic or mechanical means (including photocopying, recording, or information storage and retrieval) without permission in writing from the publisher.

Library of Congress Cataloging-in-Publication Data

Decety, Jean.

The moral brain : a multidisciplinary perspective / Jean Decety and Thalia Wheatley.

   p.  cm.

Includes bibliographical references and index.

ISBN 978-0-262-02871-4 (hardcover : alk. paper)

ISBN 978-0-262-32759-6 (retail e-book)

1. Cognitive neuroscience. 2. Neuroscience--Social aspects. I. Wheatley, Thalia, 1970- II. Title.

QP360.5.D43 2015

612.8'233--dc23

2014029653

d_r1

Contents

Introduction: The Complexity of Moral Cognition Requires Multiple and Converging Levels of Analyses

I    Evolution of Morality

1    The Evolution of Morality: A Comparative Approach

Laurent Prétôt and Sarah Brosnan

2    Adaptationist Approaches to Moral Psychology

Andrew W. Delton and Max M. Krasnow

3    Partner Choice and the Evolution of a Contractualist Morality

Nicolas Baumard and Mark Sheskin

II    Motivations of Morality

4    Is the Moral Brain Ever Dispassionate?

Jesse Prinz

5    Devoted Actors and the Moral Foundations of Intractable Intergroup Conflict

Scott Atran and Jeremy Ginges

6    Why We Cooperate

Jillian Jordan, Alexander Peysakhovich, and David G. Rand

III    The Development of Morality

7    The Infantile Origins of Our Moral Brains

J. Kiley Hamlin

8    Mechanisms of Moral Development

Joshua Rottman and Liane Young

9    The Neurocognitive Development of Moral Judgments: The Role of Executive Function

Ayelet Lahat

10    Girl Uninterrupted: The Neural Basis of Moral Development among Adolescent Females

Abigail A. Baird, and Emma V. Roellke

IV    The Affective and Social Neuroscience of Morality

11    Neural Correlates of Human Morality: An Overview

Ricardo de Oliveira-Souza, Roland Zahn, and Jorge Moll

12    The Cognitive Neuroscience of Moral Judgment and Decision Making

Joshua D. Greene

13    Neuromodulators and the (In)stability of Moral Cognition

Molly J. Crockett and Regina A. Rini

V    Psychopathic Immorality

14    Immorality and the Adult Brain

Rheanna J. Remmel and Andrea L. Glen

15    The Moral Brain: Psychopathology

Caroline Moul, David Hawes, and Mark Dadds

VI    Considerations and Implications for Justice and Law

16    Neuroscience versus Phenomenology and the Implications for Justice

Thalia Wheatley

17    The Equivocal Relationship between Morality and Empathy

Jean Decety and Jason M. Cowell

Contributors

Author Index

Subject Index

Introduction: The Complexity of Moral Cognition Requires Multiple and Converging Levels of Analyses

Over the past decade, there has been an explosion of empirical research on moral cognition from a variety of fields. Collectively, this research has captured human moral sensibility as a sophisticated integration of cognitive, emotional, and motivational mechanisms shaped through evolution, development, and culture. Among the most exciting and novel findings and theories, evolutionary biologists and comparative psychologists have shown that moral cognition has evolved to facilitate cooperation and smooth social interactions and that certain components of morality are present in nonhuman animals. Developmental psychologists have devised ingenious paradigms demonstrating that the elements that underpin morality are in place much earlier than we thought and clearly in place before children turn two. Social neuroscientists have begun to map brain circuits implicated in moral decision making and identify the contribution of neuropeptides to moral sensitivity. This research is beginning to uncover how changes in brain chemistry and connectivity realize changes in moral behavior.

The intent of this book is to provide an overview of the current research on the moral brain and examine this fascinating topic from a range of relevant interdisciplinary perspectives. These perspectives include anthropology and neurophilosophy, evolution, development, social neuroscience, psychopathology, and justice and the law. Given the increasing interest in the neuroscience of moral cognition in recent years in both academia and the general public, we believe it is time for a new volume that brings together this new knowledge in a single, concise source.

The Moral Brain addresses the basic questions regarding morality by beginning with a section on the Evolution of Morality. In the first chapter, Prétôt and Brosnan explore the precursors of human morality that exist in other species such as inequity detection and behavioral contagion and suggest how future research may best determine the extent of these evolutionarily older moral foundations. Although they agree that precursors in other species exist, Delton and Krasnow argue in chapter 2 for uniquely human adaptations that facilitate social exchange, including abilities to pool resources, detect free riders, and evoke group-level condemnation. In chapter 3, Baumard and Sheskin further posit that evolutionary pressures honed a uniquely human contractualist morality—one that maximizes cooperative relationships via a socially tuned sense of fairness. They argue that this sense of fairness predicts moral decisions that appear irrational in terms of a utilitarian framework but are in fact rational if considered through the lens of likely future interaction.

Motivations of Morality, the second section, focuses on the drives and emotions that fuel moral thought and behavior. Prinz begins the section with a discussion in chapter 4 of whether the moral brain is ever dispassionate. Through a comprehensive review of recent research, he suggests that Hume was right: Moral conclusions cannot be derived from reason alone but are grounded in the passions. In chapter 5, Atran and Ginges explore how principles held so strongly by a culture as to be considered sacred values can lead to the emergence of devoted actors willing to commit acts of extreme sacrifice to uphold them. Jordan, Peysakhovich, and Rand view cooperation as a core motivational principle for human morality in chapter 6, echoing earlier chapters proposing that evolutionary pressures honed behavior for social exchange (chapters 2 and 3). They conclude by raising a number of open questions for future research such as how reputational concerns may incentivize cooperation and when and why people who have not been harmed by selfish behavior will still punish the actor, even at considerable personal cost.

The Development of Morality, from infancy to adolescence, is the focus of the third section. Hamlin begins the section by summarizing recent research that pushes against the traditional view of late-developing moral sensibility. Pointing to her own and others’ research, she establishes that infants are sensitive to fairness and prosociality and that even newborns evince a rudimentary form of empathy, suggesting a biological preparedness for a moral sense. This idea of biological preparedness is developed further in chapter 8 by Rottman and Young, who suggest that innate intuitions form the structure of moral cognition, which is then diversified through sociocultural learning. They stress the benefits of developmental research to help uncover the functional architecture of the moral brain. In chapter 9, Lahat looks within this architecture to examine the processes collectively termed executive function that subserve moral reasoning. Emerging in the preschool years and developing throughout adolescence and into adulthood, executive function is associated with understanding the distinctions between moral and social conventional violations. Baird and Roellke (chapter 10) round out the section on development by focusing on adolescence as a sensitive period of neural maturation that serves to integrate visceral emotion and social cognition. They draw particular attention to neurobiological modulators (e.g., sex hormones) as a principal organizer of neural activity in adolescence and call for future research to consider these biological changes in tandem with the individual differences that determine how they manifest in moral cognition.

The fourth section of this volume, The Affective and Social Neuroscience of Morality, explores recent research on the neural mechanisms of moral cognition. In chapter 11, de Oliveira-Souza, Zahn, and Moll demonstrate the multidimensional nature of moral cognition through a comprehensive overview of lesion and neuroimaging research that highlights distinct cortical and subcortical brain areas associated with various component processes. In chapter 12, Greene conceptualizes the neural underpinnings of morality in terms of more general cognitive processes and discusses his dual-process model in which automatic and controlled processes underpin emotional and utilitarian judgments, respectively. Crockett and Rini (chapter 13) complete this section by reviewing evidence that neurotransmitters and hormones influence cognitive processes on which moral decisions depend. They end with a thought-provoking discussion of the myriad normative and ethical questions that emerge from considering how drugs may be used instrumentally to shape moral thought and behavior.

Psychopathic Immorality is addressed in the fifth section. Remmel and Glenn (chapter 14) begin by exploring how morality is defined and measured in psychopathy and antisocial personality disorder and then review the literature on how these disorders affect neural mechanisms underlying cognitive processes that, in turn, explain suboptimal judgment and behavior. In chapter 15, Moul, Hawes, and Dadds complement this review by adding a discussion of dysfunctional cognitive processes and traits associated with oppositional defiant disorder and conduct disorder in children, with particular attention to the striking deficits in experiencing and recognizing fear. They conclude with the hope that greater scientific understanding will shift public conception from thinking of psychopaths as monsters to a more informed view that spurs the discovery of interventions and treatments.

The final section translates the hope for a more nuanced and biological understanding into Considerations and Implications for Justice and Law. In chapter 16, Wheatley explores how findings from neuroscience are often at odds with our intuitions and that, in these cases, judicial decisions must increasingly align with scientific evidence. As previous chapters have also intimated, she concludes that a more biological understanding should promote both humility and more humane treatment but that such an understanding does not necessitate a complete overhaul of the judicial system. Decety and Cowell (chapter 17) complete this edited volume with a provocative call to rethink empathy (and its relation to morality) as a constellation of dynamic processes with distinct evolutionary roots rather than as monolithic and stable components of human morality. This view nicely echoes the motif repeated throughout this volume that multiple and converging levels of analysis will best advance our understanding of the myriad biological, cognitive, developmental, and social processes that comprise human moral cognition.

The lesson from all this new knowledge is clear: human moral behavior cannot be separated from human biology, its development, and evolutionary history. As our understanding of the human brain improves, society at large, and justice and the law in particular, are and will be increasingly challenged. Discoveries in affective and social neuroscience will soon impact our legal system in ways that hopefully lead to a more cost-effective, humane, and flexible system than we have today.

I    Evolution of Morality

1

The Evolution of Morality: A Comparative Approach

Laurent Prétôt and Sarah Brosnan

New information that’s accumulating daily is blasting away perceived boundaries between human and animals and is forcing a revision of outdated and narrow-minded stereotypes about what animals can and cannot think, do, and feel. We’ve been too stingy, too focused on ourselves, but now scientific research is forcing us to broaden our horizons concerning the cognitive and emotional capacities of other animals. One assumption in particular is being challenged by this new research, namely the assumption that humans alone are moral beings.

—Marc Bekoff (2009, p. x)

Although studied for centuries in human-focused disciplines such as philosophy and political science, the study of moral behaviors in nonhuman animals (hereafter, animals) has only recently been rediscovered. Even though it is an emerging field, the study of the origins of morality, and whether or not animals are endowed with this capacity, dates from more than a century ago. In The Descent of Man (1871/1998), Darwin hypothesized that any animal whatever, endowed with well-marked social instincts, the parental and filial affections being here included, would inevitably acquire a moral sense or conscience, as soon as its intellectual powers had become as well, or nearly as well developed, as in man. Well before that, the moral philosopher Adam Smith asserted that animals are not only the causes of pleasure and pain, but are also capable of feeling those sensations (Smith, 1759/2009).

Given this early exploration into whether or not animals possess a moral sense, why is morality a domain that has been exclusively studied in humans? No doubt this is in part because of our capacity to use language for expressing moral states and sentiments to others, thus providing direct and measurable evidence of the behavior (and likely also due to a bit of homocentrism on the part of humans). Although it is clear that humans engage in moral behavior in a way that is more complex than is seen in other species, there are interesting questions related to moral behaviors that do not primarily focus on humans. This is important; not only does the study of moral behaviors in a particular species allow a better understanding of that species, but by analyzing the origins of moral behaviors in a broader range of taxa, we can better understand the evolution of morality in humans as well.

Of course, this begs the question of how we can study behaviors related to morality in species that do not possess language skills like those of humans. It is this question that we focus on in the current chapter. More specifically, our goal is to provide a brief introduction to how we can use the comparative approach to learn about the evolution of moral behaviors in humans. We focus on three questions. First, how can we study moral behavior in species that are devoid of language? Second, what is the existing evidence for moral behaviors in other species, and what behaviors can be used as indicators in those animals? Finally, assuming that other species do show aspects of moral behaviors, or their precursors, what does this tell us about humans? In this last section we delineate what the evidence to date tells us about the evolution of morality as well as what science currently is or is not equipped to address. We hope that this brief introduction will provide a starting point for those interested in further exploration of the evolution of morality.

How Do You Study Morality in Other Species?

Although human morality has been debated for centuries, moral psychology has only emerged in the last few decades. The initial approach, the cognitive view of morality, focused on moral reasoning (see Piaget, 1932/1965). However, this approach limits the study of morality to those species that are cognitively advanced, such as humans, which makes empirical investigations in other animal taxa nearly impossible. More integrative views that combine approaches focusing on both evolutionary function and cognitive mechanisms have emphasized the study of moral emotions in order to explain moral behaviors. For instance, Haidt’s (2001) model suggests that individuals engage in moral reasoning and make decisions based on spontaneous emotional intuitions rather than through verbal discourse and reflection (Haidt, 2007). Haidt refers to these so-called moral emotions as those emotions that are linked to the interests or welfare either of society as a whole or at least of persons other than the judge or agent (Haidt, 2003). This focus on emotion, rather than linguistic reflection, opens the possibility of other, nonverbal, species engaging in moral behavior. Based on this definition, Haidt (2008) further defines moral systems as interlocking sets of values, practices, institutions, and evolved psychological mechanisms that work together to suppress or regulate selfishness and make social life possible. Again, the focus is on the regulation of selfishness and the promotion of social life, both of which are common to many species beyond humans. This synthetic and cross-disciplinary approach gives a more general and flexible view of morality and provides an operational definition that can be applied in species other than humans.

To consider moral behavior comparatively, we need to focus on behavioral mechanisms that are common to both human and animal taxa, such as the moral emotions. Before further discussing the different mechanisms of morality, however, we need to provide information about how one can compare moral behaviors in humans and other animals. A general problem for studying the evolution of behavior is that behaviors are ephemeral and, with rare exceptions, do not fossilize. Consequently, the direct observation of earlier forms of behavior is nearly impossible. In lieu of this, the comparative approach explores behaviors that were present in earlier ancestors by inference from behaviors that occur in currently living species. Behaviors are compared across a variety of species to determine which species show the behavior and whether this pattern is similar to other patterns in the ecology, social organization, or behavior of these species. In this way we can infer at what point in an evolutionary lineage the behavior evolved, by mapping the presence or absence of a behavior onto a phylogenetic tree and determining whether there is a clear point of origin of the trait. We can also determine which social or ecological factors may have been key in driving the evolution of this behavior by determining whether the trait in question correlates with other social or ecological factors in these species. Traits that are shared through common descent, inferred when all or most related species share the trait in question, are referred to as homologous, whereas those that emerged independently in species that do not share a common ancestor due to similar social or ecological pressures are referred to as convergent (Bshary, Salwiczek, & Wickler, 2007).

Thus, when we study morality or moral behaviors in other species, what we truly are exploring are the building blocks, or precursors, to moral behavior (Brosnan, 2014a; 2014b; de Waal, 2006; Flack & de Waal, 2000). These are the behaviors that support the evolution of moral behavior as it is seen in humans. Of course, the presence of one of these precursors does not mean that a species has a full sense of morality; rather, it shows us the way in which moral behavior may have evolved. These behaviors may not even be used in the same ways in species other than humans, but they provided the raw material from which the human sense of morality evolved. If we better understand the precursors on which human moral behavior was built, we may be able to extrapolate the important evolutionary pressures that have led to the behavior we see today.

What Is the Evidence for Moral Behavior in Other Species?

Typically, moral behaviors are divided into several categories. The most basic of these, and presumably the most widespread across the animal kingdom, are behaviors related to social regularity (de Waal, 2006; Flack & de Waal, 2000). These are behaviors that promote group cohesion and the smooth functioning of the social group and are, by definition, present in any group-living species. These behaviors have evolved with a multiplicity of mechanisms underlying them. For instance, some social insects solve the issue of group living through a genetically or developmentally constrained caste system, whereas other species, including primates, may solve the same issue through a flexible system that depends on the individual and the context, and may even include empathy. This variability shows us that this basic problem—how to maintain the social group—is so important that solutions have evolved multiple times that solve it in multiple ways. Of course, if we are interested in human behavior, we may be more interested in the flexible system instantiated by the nonhuman primates, but by seeing the commonalities in outcome we get a better understanding of which issues are sufficiently important that they have been solved repeatedly by evolution.

On the other end of the spectrum are behaviors related to judgment, reasoning, and moral decision making. These complex behaviors are likely limited to humans and possibly a few other species. We do see limited evidence for behaviors related to moral judgment in other species. For instance, chimpanzees engage in consolation behavior, in which an uninvolved third party approaches and affiliates with the victim of a fight following the interaction (de Waal, 1996; de Waal & Aureli, 1996; de Waal & van Roosmalen, 1979). Even within the primates this behavior seems to be limited to the apes, although there is emerging evidence in a few nonprimate species, for example, in ravens (Fraser & Bugnyar, 2010). Although there may be benefits to the consoler (Koski & Sterck, 2007), if consolation is motivated by a feeling that the victim had been inappropriately targeted, this would qualify as moral judgment. Because the possibility of moral judgments in animals is purely speculative at this stage, we do not discuss them further.

Finally, we may also study the precursors to moral behavior through specific behaviors that result in benefiting other members of the group. These are behaviors that support group living, but, unlike behaviors related to social regularity more generally, these behaviors are much less common across the animal kingdom and, in some cases, appear to be targeted. We note one very important caveat: despite the fact that these behaviors result in benefiting others, this does not mean that they are motivated by altruism or other-regarding preferences. As we have alluded to already, there are two types of explanations for any behavior, the underlying function (e.g., why did a behavior evolve?; what problem does it solve?) and the mechanism by which it does so (e.g., what are the genetic, hormonal, neural, developmental, or cognitive pathways through which the behavior is instantiated?). When we discuss behaviors that benefit others, we are referring to the functional outcome of the behavior, not the mechanism. That is, we focus on whether this behavior provided a benefit to another individual, not whether the behavior was intended to do so. Below we consider the evidence for three particular behaviors that are other-oriented: reciprocity, prosocial behavior, and inequity. Although these behaviors may not be moral in and of themselves, they represent the sorts of behaviors that may have provided the evolutionary foundation for our own moral system.

Reciprocity

One way in which animals benefit other individuals is through reciprocity. Reciprocity, or reciprocal altruism, occurs when individuals alternately provide benefits to one another. This idea, first suggested by Robert Trivers (1971), provides an explanation for the evolution of cooperation because animals receive benefit in the long term from benefits that they provide to others now; reciprocity provides an overall benefit as long as the short-term cost that A undergoes from helping B now is exceeded by the benefit A will receive from B’s return help over the long term. Again, reciprocity explains how benefits directed to others might evolve but does not mean that the individuals intend to provide benefits or that they understand the ramifications of their actions. Many examples of reciprocity are clearly rather inflexible behavioral patterns that do not indicate any understanding on the part of the actor.

Despite the long history of studying reciprocity in animals, there is little agreement on its prevalence. Using chimpanzees as a case study, despite the evidence of long-term exchange of goods and services in the wild (Gomes & Boesch, 2009), there is surprisingly little evidence of reciprocity in controlled experiments (Brosnan et al., 2009; Melis, Hare, & Tomasello, 2008). That being said, one of the challenges of studying reciprocity in a species with a high degree of cognitive flexibility is that reciprocity is not likely to occur in all circumstances and may require specific conditions that are not often met in typical experiments. For instance, it may be that individuals are more likely to reciprocate when they have the opportunity to choose their partners and when reciprocity can happen on a longer time scale than is typically found in laboratory studies. One captive study that did find evidence of reciprocity in chimpanzees involved observing the correlation between grooming and food sharing within an entire group of chimpanzees across their day. De Waal found that chimpanzees that groomed one another in the morning were more likely to share food in the afternoon. This effect was specific to the grooming recipient sharing food with the groomer in the afternoon, but not the reverse, and the grooming recipient’s sharing was specific to the groomer, implying that this was contingent reciprocity rather than generalized good will (de Waal, 1997). The apparent flexibility in the chimpanzees’ reciprocity makes this behavior close to that which we associate with moral behavior in humans.

However, lest we give the impression that flexible reciprocity is limited to larger-brained species or nonhuman primates, we note that some of the more impressive examples of reciprocity are found in other species. For example, although we have previously discussed direct reciprocity, another form of reciprocity is generalized reciprocity, in which individuals help one partner in response to help received from another. This mechanism might contribute not only to the maintenance of good individual relationships within an existing social group but possibly even among individuals outside of this immediate group. This may be particularly important for species in which it can be useful to welcome previously unknown individuals into the social group. The only species that has been demonstrated to engage in generalized reciprocity, other than humans (Bartlett & DeSteno, 2006), is rats (Rutte & Taborsky, 2007), which also engage in direct reciprocity that is influenced by the partner’s previous behavior (Rutte & Taborsky, 2008). Thus, although not every species that shows reciprocal behavior will comprehend it as such, the evolutionary pressures that led to reciprocal behavior nonetheless selected individuals to behave in ways that benefited their partners. Such behavior provides a foundation on which human moral behavior could have evolved.

Prosocial Behavior

Although some behaviors that benefit others may have evolved in the context of reciprocity, in other cases individuals may help others in situations that are not explicitly reciprocal. Such prosocial behavior¹ in animals occurs both in the realm of food sharing, which is relatively rare in the primates (Jaeggi & van Schaik, 2011), and social interactions. For instance, nonhuman primates use a range of political maneuvers and manipulations in order to intervene in conflicts and maintain order and cohesion in a group (Proctor & Brosnan, 2011). For example, policing behavior, which occurs both in the wild (Boehm, 1994) and in captivity (chimpanzees: de Waal, 1982/1998; 1992; macaques: Flack, de Waal, & Krakauer, 2005; Flack, Girvan, de Waal, & Krakauer, 2006), is often impartial, with the apparent goal of minimizing fighting within the group rather than supporting one individual over another or promoting one’s own agenda. Additionally, there is extensive anecdotal evidence of animals, particularly apes, helping one another (de Waal, 2006). However, without controlled experiments it is not possible to rule out alternative explanations for these prosocial outcomes, which has led to a recent interest in investigating prosocial behavior experimentally.

These experiments typically rely on giving animals a choice about whether or not to provide food rewards to members of their social group (reviewed in Cronin, 2012). These studies are difficult to interpret. This is likely in part because, as with reciprocity, experimental results do not match the expectations derived from natural observations, possibly because prosocial behavior, too, may not be as likely to occur in the laboratory setting as in natural circumstances. Additionally, procedures typically vary across studies, making them difficult to compare. One interesting finding has been that, at least in chimpanzees, prosocial behavior is more likely in helping situations than in food-sharing situations (e.g., Warneken & Tomasello, 2006), which may be an indication of the contexts in which prosocial behavior is more important in the wild. Additionally, it has been hypothesized that prosocial behavior is more likely to evolve in cooperative breeders, those species in which both the male and female, and often adult offspring, raise current offspring, because of the interdependency inherent in that social system (Hrdy, 2009; van Schaik & Burkart, 2010). Further explorations of the contexts in which prosocial behavior is most common will help to clarify those situations in which behaviors that assist others, a bedrock of moral behavior, are the most essential.

Inequity

One advantage of being a socially living organism is constantly having information about the outcomes of others. This can provide a major advantage if, for instance, a group member develops a better way of processing a food that you can then learn and benefit from. Such social learning has been widely documented across the animal kingdom (Heyes & Galef, 1996). However, the ability to compare one’s outcomes to those of others may also be an advantage if one is trying to judge the relative benefit of multiple partners. It has been hypothesized that individuals who can judge their outcomes as compared to those of others have an advantage in choosing cooperative partners, in that they can leave those with whom they earn relatively less benefit and seek out those with whom they might do better (Brosnan, 2011; Fehr & Schmidt, 1999). Such a negative response to inequity has been documented in some species besides humans using an experimental test in which subjects must complete a task with a human experimenter in order to receive a food reward that may be the same as or different from a social partner’s reward for the same task. Intriguingly, reactions to inequity occur quite commonly in species that routinely cooperate with nonkin but do not occur in closely related species that do not cooperate, indicating that one function of recognizing inequity is to judge the value of one’s cooperative partners (Brosnan, 2011; Price & Brosnan, 2012). Additionally, the inequity response is not seen in cooperatively breeding primates, possibly because of the high costs of finding a new partner in such an interdependent relationship (Freeman et al., 2013).

Of course, once a negative response to inequity has evolved, it is now possible that individuals may also learn to recognize when they get more than a partner. Although reacting against getting more leads to an immediate loss, it may provide a long-term benefit in terms of an improved reputation (Frank, 2001) or a better relationship with that social partner. Individuals who are able to anticipate that their partners will become frustrated and adjust their behavior should be better able to maintain beneficial partnerships (Brosnan & de Waal, 2012). In fact, there is evidence that chimpanzees recognize when they are advantaged as compared to a partner (Brosnan, Talbot, Ahlgren, Lambeth, & Shapiro, 2010), and capuchin monkeys who share a preferred outcome are almost three times as successful at a cooperative task compared to those partnerships in which one monkey dominates the more preferred reward (Brosnan et al., 2006). More than responding negatively to getting less, this response to overcompensation hints to the roots of moral behavior in other species.

Moral Emotions: Empathy

Empathy is the cognitive capacity to feel and perceive others’ emotions (Preston & de Waal, 2002). Of course, we cannot measure emotion or perspective taking in other species except through their instantiated behavior (because they cannot tell us what they think), so when we talk about empathy in other species, what we really mean is behaviors that indicate an understanding of another’s emotions, desires, or goals. Unfortunately, one challenge of studying empathetic behaviors is that these behaviors are very difficult to elicit in the laboratory, especially without utilizing situations that the animals find aversive. Thus, the majority of evidence comes from anecdotal reports of subjects’ behavior (e.g., de Waal, 2006). For instance, apes, but not monkeys, show targeted helping, or the ability to understand what another individual wants and then to provide him or her support to achieve the goal. There are more anecdotes in apes than any other taxa, probably due to a combination of research effort and the assumption that human-like behaviors are most common in humans’ closest ancestors. Nonetheless, other species also show evidence of empathetic behavior, such as in situations in which a group member is ill, injured, or dead (McComb, Baker, & Moss, 2006; Simmonds, 2006). One challenge to the anecdotal reports is that there are always alternative explanations that cannot be ruled out without experimental controls. Consequently, researchers have focused on behaviors that may be related to empathy that can be studied experimentally.

Consolation, argued to be an indicator of cognitive empathy, occurs when a victim of a fight is approached by a bystander who provides support (e.g., grooming or other affiliative behaviors). This provides stress reduction to the victim as well as the consoler (Koski & Sterck, 2007). This behavior occurs in apes (Romero, Castellanos, & de Waal, 2010) but has not been seen in monkeys (de Waal & Aureli, 1996), leading to the hypothesis that some empathetic behaviors require the more advanced cognition seen in the apes. Additionally, contagious yawning, a behavior that has been linked to empathy in humans, is also seen in several other species. Notably, chimpanzees shown video of group members and strangers yawning are more likely to yawn when viewing their group members, possibly indicating greater empathy with nonstrangers (Campbell & de Waal, 2011).

Given the difficulty in finding experimental evidence of empathy in primates, it is notable that the best evidence to date comes from rodents (Langford et al., 2006). Church first reported evidence of emotional reactions in rats a half-century ago, noting that individuals quit pressing a lever to obtain food if a partner experienced electric shocks, sometimes going without food for extended periods (Church, 1959). Langford et al. (2006) showed that mice watching a conspecific get shocked made the subjects more sensitive to their own pain (also from a