The closed circle of empathy: mirror neuron system activation and anterior EEG asymmetries in response to outgroup members. Jennifer N.

Transcription

1 The closed circle of empathy: mirror neuron system activation and anterior EEG asymmetries in response to outgroup members. by Jennifer N. Gutsell Master s thesis submitted in conformity with the requirements for the Masters of Arts and Science Department of Psychology, University of Toronto, 2009 Copyright by Jennifer Nadine Gutsell (2009) i

2 The closed circle of empathy: mirror neuron system activation and anterior EEG asymmetries in response to outgroup members. - Jennifer N. Gutsell, Department of Psychology, University of Toronto, 2009 Abstract Empathy varies with similarity and familiarity of the other. Since outgroups are seen as dissimilar to the self, empathy might be restricted to the ingroup. We looked at two neural correlates of empathy: mirror neuron system activation as indicated by electroencephalographic mu suppression and prefrontal alpha asymmetry. Non black participants watched videos of ingroup and outgroup members acting and expressing emotions, and then acted and experienced emotions themselves. Due to methodological problems, mirror neuron system activation was not obtained. However, anterior asymmetries indicated avoidance motivation during the experience of sadness and the mere observation of sad ingroup members while participants did not show anterior asymmetry when observing the black outgroup. These findings suggest that empathy is bounded to a closed circle of similar others. ii

3 Table of Contents Abstract...ii Table of contents....iii List of Tables....iv List of figures....v Introduction Theoretical Background... 2 Empathy a definition... 2 How do we empathize? The Perception Action Model of empathy... 4 The stages of empathy... 5 The limits of empathy moderators for empathic responses... 8 The mirror neuron system a neural account for vicarious emotions and the basis of empathy moderators for empathic responses Prejudice and the distinction between us and them Perceiving others as different Social neuroscientific methods to measure empathy Measuring Mirror Neuron System activation Measuring vicarious prefrontal alpha asymmetries Overview Method Participants Procedure Stimulus Materials Measures Measures of ingroup favouritism Measures of empathy EEG data acquisition and processing Results Mu suppression Anterior Alpha Asymmetry Behavioural measures Correlation with empathy.30 Correlation with ingroup favouritism IAT, MRS and IOS...31 Discussion Limitations and further directions Conclusions References iii

4 List of Tables Table 1 Correlations between anterior alpha asymmetry scores and the measures of ingroup favouritism and empathy. 5 iv

5 List of Figures Figure 1 The human MNS and its main visual input in action understanding and imitation Figure 2 Anterior alpha asymmetry scores during the two emotion conditions (Sad, Happy) for ingroup, self and black v

6 1 I am a Jew. Hath not a Jew eyes? Hath not a Jew hands, organs, dimensions, senses, affections? --From The Merchant of Venice (III, i, 60-63) In the quote above, the character of Shylock pleads for empathy and equal treatment noting that Jews bleed when pricked, laugh when tickled, and killed when poisoned. Given our shared humanity, then, why does prejudice seem so inevitable? To answer this question, the current study looks at the basic processes involved in prejudice by taking a closer look at brain activity. I propose that the neural systems involved in empathy and action understanding are less responsive to outgroup members than ingroup members, leading people to ignore the shared humanity of others. Empathy is the capacity to recognize and understand other people s experiences, needs, and goals, and thus facilitates social understanding and cooperation. Empathy is bounded, however: it varies as a function of similarity and familiarity of other people (Preston & de Waal, 2002). According to self-categorization theory (Turner, 1987), ingroup favouritism and prejudice result from the intersection between one s self and one s ingroup. Once one identifies with a group, the self and the group merge to become interchangeable. The self, importantly, overlaps with the ingroup, but not with the outgroup. This overlap facilitates perspective taking and empathic reactions. On the other hand we might be less sensitive to the feelings of outgroup members and less likely to take their perspective. If people do not feel other people s pain, the door for discrimination is wide open. The aim of the current study is, first, to investigate whether empathy is bounded to ingroup members and, thus, excludes outgroup member and, second, to find a neural account for why empathy is bounded. To achieve these goals, this study draws on neuroscientific research on empathy and perspective taking.

7 2 In what follows, I will first review research on empathy and which factors promote and prevent empathy. Second, I will present a neuroscientific view on empathy and discuss its potential origins in our evolutionary history. Third I will discuss prejudice and its causes. I will further describe the concept of self-other overlap and dehumanization of outgroups, and connect them to prejudice. I propose that the perceived distance between groups impairs empathy towards these groups and that this is reflected in the neural processes underlying empathy. I will, then, discuss two neural correlates and potential measures of empathy mirror neuron system activity measured by EEG mu rhythm suppression and asymmetries in the activity of the prefrontal cortex measured by anterior alpha asymmetries. Third, based on this theoretical background, I will develop an appropriate research method for examining the role of the mirror neuron system in prejudice. I will then describe the research design and the empirical and analytical methods. Finally I will present the results and discuss their implications. Theoretical Background Empathy - a definition Empathy is generally referred to as the ability to feel with others (Batson et al., 1997). Usually, when we see others in pain, we suffer along with them and this is one of the building blocks of human and animal societies (McDougall, 1923). In addition to this fundamental function, empathy is the basis for numerous important social processes (Carr, Iacoboni, Dubeau, Mazziotta & Lenzi, 2003). First, empathy functions as the driving force behind helping behavior (Dovidio, Allen, & Schroeder, 1990; Batson et al., 1997) and other prosocial behavior, such as cooperation, moral sense, altruism, and justice (Vignemont, & Singer, 2006). Second, in addition to its effects on prosocial behavior, empathy promotes understanding and, therefore, influences people s attitudes towards others (Batson et al., 1997). Feeling empathy for someone elicits a concern about the welfare of the other person.

8 3 This increase in concern persists even after empathy lessens (Batson, Turk, Shaw & Klein, 1995). Third, empathy helps one to predict others future behaviour and to understand their motivational states and goals (Vignemont, et al., 2006). Therefore, empathy is a very effective tool for social understanding and leads to smooth social interactions. Finally, empathy facilitates social communication. When we empathize with others, we tend to imitate or mirror their intonations, gestures, and postures. This imitation elicits fondness and affiliation in others (Lakin & Chartrand 2003). Similarly, perceiving that others empathize with us improves our opinion about them (Chartrand, Bargh, 1999). Because of its importance people have researched empathy for many years (Batson, Fultz, & Schoenrade, 1987, Cialdini, Brown, Lewis, Luce, & Neuberg, 1997, Hume 1888, Lipps, 1903 (as cited in Preston, & de Waal, 2002). Despite this interest, researchers still disagree about what constitutes empathy (Preston, & de Waal, 2002). Some define empathy as an affective response more appropriate to another s situation than one s own (Hoffman, 2000), affect sharing (Preston, & de Waal, 2002), or the sensitivity to and understanding of the mental states of others (Smith, 2006). These relatively broad definitions subsume a whole array of related sub concepts that can be separated into two categories: emotional empathy and cognitive empathy. Emotional empathy highlights the aspect of feeling others emotions. It includes more basic processes such as emotional contagion or personal distress (e.g. I feel sad because I see that you feel sad) and higher order processes that go beyond the mere mirroring of others emotions. For example, empathic concern (Batson, Fultz, & Schoenrade,1987) results from further processing based on the information obtained from vicarious emotions (e.g. I feel sorry for you because you are sad). Cognitive empathy, on the other hand, is the understanding of the other s emotional state as opposed to simply vicariously feeling with the other. It includes phenomena such as cognitive perspective taking (e.g. because I know you and your situation I

9 4 infer that you are sad) and theory of mind. Sometimes a more restrictive definition of empathy is necessary to allow precise hypotheses and predictions for research purposes (Batson et al., 1987, Vignemont, & Singer (2006). However, following Preston and de Waal s (2002) approach, I see empathy as a concept that joins all phenomena that are based on the same underling process the vicarious experience of the emotions of another person. Such a process based concept of empathy defines empathy in even broader terms than the definitions discussed above. It includes all levels of empathy related phenomena starting from emotional contagion to sympathy, guilt, cognitive empathy, and finally even helping behaviour. It also links empathy to related behaviours such as imitation and priming. Hence, using a process based definition of empathy enables us to look at the whole array of behaviours that constitute much of our social nature and, at the same time, to focus on their joint evolutionary origins and neural basis (Preston, & de Waal, 2002). How do we empathize? The Perception Action Model of empathy According to Preston and de Waal (2000) empathy is based on the same mechanism as motor behaviour the perception-action mechanism. Actions and the mere perception or imagination of the same actions share common representations (Prinz, 1987). Through these common representations, observing behaviour automatically activates and facilitates the same behaviour in the observer. For example, hyenas are 70% more likely to drink when they see co specifics drinking (Glickman et al. 1997). Further, Muesseler and Hommel (1997) found that participants were unable to perceive a stimulus that represented a certain action (e.g. right key press) while they performed that same action (e.g. pressing the right key), even though they could easily perceive the stimulus when it did not correspond with the action (e.g. while pressing the left key). These findings show that, because perception and action share the same

10 5 representation perception and thus are incompatible with each other, perception is blocked when the representation is used for acting (Chartrand, & Bargh, 1999). Linking perception, imagination and action through a common representation is evolutionary highly adaptive since it enables the organism to react quickly and appropriate to its environment (Preston, & de Waal, 2002). Social animals and especially primates, who rely heavily on their co specifics for survival, use the action perception link to navigate through their complicated social systems (Preston, & de Waal, 2002). When someone (the subject) observes another (the object), the subject has access to the object s inner states, because the mere observation activates the same neural and bodily representations in the subject. Through this mechanism the subject feels with the object; it happens without intention or consciousness, and that is what we call emotional contagion. Chartrand and Bargh (1999) proposed that the action perception link consists of three steps. First, the subject observes the targets facial expression and bodily postures, in a second step this observation activates the subjects own representations. Finally, this activation increased the tendency for the subject to behave in the same way as the object. As proposed in the facial feedback hypothesis (Izard, 1990, James, 1913, Laird, 1974), once the subject has adopted the object s expressions and posture, these elicit bottom-up processes that elicit the correspondent emotions. Therefore, by enacting the object s emotions, the subject experiences these emotions the ground for empathy is laid. This emotional contagion is the most basic process in empathy and seems to be biologically hard wired (Atkinson, 2002). However, as soon as higher order cognitive processes become involved more sophisticated forms of empathy evolve. The stages of empathy Empathy consists of three different stages: Emotional contagion, empathic concern and empathic perspective taking (de Waal, 2008). Emotional contagion of negative emotions

11 6 results in personal distress. This stage is not altruistic. Instead, it is self focused; since the negative feelings, elicited by the other, cannot be distinguished from one s own feelings. The observer feels distressed but does not, or cannot, take the next step of distancing him- or herself from these feelings. This self centered empathy leads to the selfish motivation to alleviate one s own pain. One can ease one s pain by either reducing the distress of the other through helping, or by leaving the distressing situation and turning one s back to the sufferer (Batson, Fultz, Schoenrade, 1987). This negative side of personal distress was shown by rats who failed to press a button to save another rat that suffered from electric shock. Instead of helping the other rat, they crunched fearfully in the furthest corner expressing high levels of distress (Rice, 1962). For many species, emotional contagion is the only form of empathy and it often proves to be useful, for instance, when a flock of birds flies away from a predator after hearing the distress signals of a flock member, or when a rat mother comes to help one of its pups squeaking in distress. The next evolutionary step of empathy and the next step in child development is empathic concern. Here, while the subject feels the emotions of the object, the process does not stop. Instead, the subject is aware that the object is the source of its emotions and can appreciate and comprehend the other s situation (De Waal, 2008). This new distinction between internally and externally generated emotions opens the door for more sophisticated empathic emotions emotions such as guilt, compassion, sorrow, but also spitefulness, resentment and envy. Often, empathic concern evokes an other-oriented, altruistic motivation to alleviate the other s distress (Batson 1991). However, at this stage, real empathy, or what the lay person would consider to be empathy, is not yet achieved. We generally speak of empathy only when it involves perspective-talking. Only when we feel with the other and consequently feel for the other, and we understand the other and his situation, we say that someone truly empathizes with another

12 7 (de Waal, 2008). Hence, top down processes are involved in empathy. The subject takes the object s perspective and imagines their mental state and situation to understand the emotions the subject sensed from the object through emotional contagion. Thus, the third and last stage of empathy is empathic perspective taking the cognitive process of taking the other s perspective plus empathic concern. Empathic perspective taking can result in targeted helping, which is helping adapted to the specific needs and goals of the other (de Waal, 2008). This happens, for instance, when a mother hears her baby crying. Initially feeling distressed herself; she quickly shifts perspectives and consequently feels compassion with the baby and a strong motivation to alleviate the baby s distress. She, then, assesses the baby s situation, taking into account what she knows about its preferences, goals, and behavioral patterns, to infer what caused the distress and what can reduce it. She might then come to the conclusion that the baby is hungry and will take steps to feed the baby. Without the initial vicarious distress, however, the mother would lack the basis for all subsequent steps in her progress to helping. Because she would not feel with the baby, she would see her babies distress signals, but would not understand what they mean. Although she could try to infer what they mean by top down processing, for example recollecting what she knows about babies and that their crying indicates that they are in need of something. Nonetheless, she would still lack the emotions necessary to fuel the motivation to help. Research on anti-social personality disorder illustrates this point. Individuals diagnosed with this disorder are said to lack the ability to feel with others. They are able to severely harm and sometimes kill others because they are unresponsive to other s distress signals (Blair, 1997). Despite their lack in empathic concern, individuals with anti-social personality disorder have intact cognitive functions and are fully capable of cognitive perspective taking (Blair, 2008). Thus, without the ability to feel with and for others, all cognitive reasoning is useless. The experience of vicarious emotions is vital for all subsequent stages of empathy. Recent findings, however, suggest, that this basic and

13 8 automatic process is not as universal as one would expect. Empathy was shown to be biased and restricted by certain factors and this might even start at its crucial basic process. The limits of empathy moderators for empathic responses. Whether we empathize with someone or not depends on perceived similarity (Cialdini, Brown, Lewis, Luce, & Neuberg, 1997), familiarity with the target (Cialdini, et al. 1997), need for nurturance and protection of the target (Batson, et al., 2005), and affiliation with the target (Vignemont & Singer, 2006). For example, in an experiment on the effects of similarity on empathy, participants where led to believe that an ostensible second participant was similar or dissimilar to them. They, then, saw the other participant getting electric shocks. Participants showed heightened arousal and reported more empathic emotions when the other was similar as compared to when he was different. Apes, also, empathize more with familiar apes who received electric shocks then with unfamiliar apes (Miller, Murphy, & Mirky, 1959). Moreover, Cialini, et al. (1997) found that in humans, emphatic concern for others is eliminated when one controls for oneness the degree to which participants perceive themselves in the other. The reasons why similarity, familiarity and affiliation promote empathy lay in our evolutionary history. According to the concept of inclusive fitness (Hamilton, 1964, as cited in Cialdini, et al., 1997), individuals do not act to secure their own welfare but to secure the welfare of their genes. Hence, from an evolutionary perspective, it is irrelevant whether one survives or two of one s siblings survive. In both cases, the contribution of one s own genes to the gene pool is the same. From the perspective of evolution, then, empathy and prosocial behaviour should be determined by their contribution to reproductive success in ancestral environments. Hence, one can preserve one s genes by promoting the survival of those who share one s genetic make-up. Since people can promote their own evolutionary success by

14 9 helping relatives (Sime, 1983), inclusive fitness can explain altruistic behaviour within families. When a mother saves her children by risking her own death, according to inclusive fitness, this is a smart thing to do. Following this strategy it is easy to determine who to help and who not to help when dealing with relatives. When asked how they would respond to various situations in which someone needed help, participants expressed more motivation to help close relatives and especially younger and healthy ones (Burnstein, Crandall, & Kitayama, 1994). Relatives are not the only ones with whom we share genes. Our genetic makeup overlaps with other people as well; sometimes even with strangers. At one point in our evolutionary history we had a common ancestor with everyone. What counts is the degree of genetic overlap we share with others. Since this degree of genetic overlap is impossible to detect, we must rely on cues that usually come along with genetic similarity. The more similar someone is to us, the more likely it is, that he or she shares at least some of our genes. Therefore, similarity is an important factor leading to empathy and prosocial behaviour (Krebs, 1991). Natural selection not only operates on individuals, it can operate on groups as a whole. Humans can sometimes increase their reproductive success by protecting their groups interests as opposed to the interests of other groups (Wilson & Sober 1998). This could explain, at least in some part, why we empathize with and help others who are unrelated but socially connected to us. Knowing that similarity influences empathy, an important question is at which stage of empathy does similarity moderate the empathic reaction? Most behavioural studies cannot provide an answer to these questions since they investigate the result of the process through empathic behaviour or self report and these approaches are insufficient to distinguish between the different stages of empathy. However, research on the neural basis of empathy suggests that the most basic processes in empathy are sensitive to similarity, familiarity and affiliation

15 10 of the object. This research examines the mirror neuron system - a neural system said to be the basis for the perception-action link and which can provide useful insight in the basic mechanisms underlying empathy. The mirror neuron system a neural account for vicarious emotions and the basis of empathy The idea of the perception-action mechanism had been around for several years before it gained additional support from the neurosciences. While recording single cell activity in the monkey premotor cortex, an area usually responsible to retrieve the appropriate motor act in response to sensory stimuli, Rizzolatti, Fadiga, Fogassi, and Gallese (1996) discovered that premotor neurons fire when the monkeys grasped food and when the monkeys simply observed the experimenter doing so. Since, during observation, these cells mirror the activation patterns that produce that same action, they have been called mirror neurons. Further research on mirror neurons revealed that they only respond to biological, objectdirected actions (Rizzolatti, & Luppino, 2001). For example, mirror neurons are unresponsive to the mere sight of an object and actions without an object being present. Further, an action performed by a mechanical device is not effective either.these specific demands for the subject, action and object suggests that mirror neurons represent goal-directed actions (Rizzolatti & Arbib, 1998). These representations enable individuals to understand and imitate others actions and goals (Rizzolatti, Craighero, 2004). After the discovery of the mirror neuron system in monkeys, the research focus shifted to humans. Behavioural, neuropsychological, and imaging studies with positron emission tomography (PET), functional magnetic resonance imaging (fmri) and electroencephalography (EEG) established that humans, indeed, have a mirror neuron system (Buccino, Ferdinand, & Lucia, 2004; Rizzolatti, & Craighero, 2004). In humans the observation of actions activates a complex network formed by occipital, temporal, and parietal visual areas. The core of the

16 11 human mirror neuron system is the rostral part of the inferior parietal lobe and the lower part of the precentral gyrus plus the posterior part of the inferior frontal gyrus (IFG) - brain regions primarily specialized in motor functions, action planning and intentions (Rizzolatti & Craighero, 2004) (Please see figure 1 for a depiction of the human mirror neuron system). Similar to the monkey s mirror neuron system, the human mirror neuron system reacts to the sight of biological movements, the abstract and general representations of actions, and it is especially receptive to intentional action (Rizzolatti, Fogassi, Gallese, 2001). With these properties, the mirror neuron system seems to serve a mapping function (Fogassi et al., 2005). Rizzolatti et al. (2001) propose that the mirror neuron system is the basis for the perception action mechanism; we understand actions when we map the visual representation of the observed action onto our motor representation of the same action. Iacoboni and Dapretto (2006) Figure 1: The human MNS (in red) and its main visual input (yellow) in action understanding and imitation. The MNS in the rostral inferior parietal lobule (IPL) is primarily concerned with the motoric description of the action. The frontal MNS located in the Prefrontal Motor Cortex (PMC) and Inferior frontal Gyrus (IFG) is more concerned with the goal of the action. The yellow and red arrows represent the flow of information from visual to motor and

17 12 prefrontal areas. The black arrows represent an efferent copy send back from prefrontal cortex to posterior Superior temporal sulcus (STS). If we want to apply the perception action mechanism to emotions and empathy, things become more complicated. The brain areas underlying the mirror neuron system are generally not involved in emotions (Iacoboni & Lenzi, 2002). Then, how can the mirror neuron system be the basis of empathy? The insula connects limbic areas, which generate emotions, with the areas involved in the mirror neuron system and, as shown by fmri studies, the insula is heavily involved in affect generation during imitation tasks. Hence, the insula is the necessary link between the action oriented mirror neuron system and emotional areas, providing a possible pathway from observation of motor behaviour, such as expressions and body posture, to empathy (Carr, et al., 2000, Iacoboni, Lenzi, 2002). Several brain imaging studies further support the action-perception model of empathy. 2 In all of these studies, mirror neuron system activation appeared almost automatically; whenever participants observed emotions, the mirror neuron system was active. But, are mirror neurons really automatically triggered every single time we see someone s emotions? As we have seen, empathy is more selective. Is this true even at this most basic level of empathy? Recent studies suggest that some kind of moderation processes determine activation of the mirror neuron system. In their research on mirror neuron system function, Oberman, Pineda, & Ramachandran (2006) showed participants videos that differed in the degree of social interaction. In the no interaction condition, participants saw three individuals standing in a circle, each of them tossing a ball in the air and catching it. In the medium interaction condition the three individuals tossed the ball to each other and in the high interaction condition the three individuals tossed the ball to each other, but sometimes they tossed it off

18 13 the screen, seemingly to the observer. Thus in the no interaction condition there was no interaction between the three individuals nor was there any interaction with the observer. In the medium interaction condition, the three individual interacted but they did not interact with the observer. Finally, in the high interaction condition, the three individual interacted and they also interacted with the observer. As measured with the EEG, mirror neuron system activation was moderated by the degree of interaction. When the participants were included in the interaction, their mirror neurons fired the most, followed by interaction without involvement of the participant, and the least activation in the no interaction condition. Hence, mirror neuron activation depends on the degree of social interaction and mirror neurons are especially active when there is face-to-face interaction. These results show that the mirror neuron system is reactive to variations in social content. Singer, et al. (2006) provided further support for the mirror neuron system s sensitivity for social content. They found evidence that mirror neuron system activation is moderated by the affective link between individuals. To manipulate liking versus disliking, they let their participants play an economic game with two ostensible other participants, who were actually confederates. One of the two confederates played unfair and the other played fair. Later, mirror neuron system activation was measured with f MRI while participants watched the confederates receive seemingly painful stimuli administered to their hands. Both, male and female participants exhibited mirror neuron system activation in pain-related brain areas when they saw fair players feeling pain. Male participants showed significantly reduced mirror neuron system activation towards the unfair players, whereas female participants showed mirror neuron activity in response to both players. At the same time only males showed increased activation in reward-related brain areas and they later expressed the desire for revenge. Taken together, research on the neural processes involved in empathy confirms the perception action model of empathy we know what others feel because we actually feel it,

19 14 and we feel their emotions because we simulate them in our brains. Even these basic mechanisms seem to be influenced by similarity, familiarity and affiliation, thus bounding empathy to certain others. This bias towards similar, familiar and affiliated others suggests that there is a fundamental difference in how our brain processes information about people to whom we have different social relations and attitudes. This might have far reaching consequences for interactions with individuals who cannot activate our mirror neuron system. We might not be as responsive to these people s needs, and less likely to understand their intentions; we might be less likely to help them, and might communicate less effectively with them. Usually our ingroup members are the ones who are similar to us, who we are familiar and affiliated with. So what about outgroups? Is it possible that we empathize less with outgroup members? Research on prejudice suggests that this might be the case. Prejudice and the distinction between us and them Prejudice can be defined as an unfair negative attitude toward a social group or a member of that group (Dovidio, & Gaertner, 1999). People prefer their ingroup to an outgroup (Perdue, Dovidio, Gurtman, & Tyler, 1990), they assign more positive attributes to the ingroup than to the outgroup (Gaertner Mann, Murrell, & Dovidio, 1989), and they show less helping behaviour towards outgroup members (Dovidio, et al., 1997, Frey, & Gaertner, 1986). Interestingly, empathy seems to be an antidote for prejudice (Batson et al., 1997; Galinsky, & Moskowitz, 2000). The determining factor for these biases might be similarity. In social identity theory, Turner, Brown, and Tajfel (1979) introduced the concept of self-categorization. People who identify with a group come to perceive themselves not as unique personalities with individual differences, but as interchangeable parts of a group. As a result, the self and the group merge and the group identity becomes an integral part of the self. When people merge with their group, they tend to stress similarities with the ingroup and

20 15 differences with the outgroup. Thus the self and the ingroup become seemingly more similar, whereas the gap between the self and the outgroup grows. Consequently, people perceive outgroup members as radically different from their own group. This distinction can even lead to the feeling that others lack typically human characteristics (Leyens, et al., 2000). As a result, people sometimes consider outgroup members as less than human. Perceiving others as different Fiske, Cuddy, Glick and Zu (2002) addressed the question, why we sometimes ignore the shared humanity of outgroup members, in their stereotype content model. According to this model the extent to which we deny others their full humanity depends on their group membership. We judge groups on two dimensions: warmth - the group intends to help and not harm us - and competence - the group is capable of enacting those intentions. Groups who are high in warmth and competence elicit respect and admiration. Mostly this is the case for one s ingroup. However, when we judge a certain group as low in warmth and low in competence, the elicited emotions are disgust, disrespect, and dislike (Fiske, Cuddy, Glick, & Zu, 2002). Such devalued groups are most likely to be seen as less than human and are often dehumanized (Harris & Fiske, 2006). Dehumanization is the most extreme form of prejudice and it applies for example to homeless people, drug addicts and sometimes, but to a lesser degree, ethnic groups and in particular Arabs and Blacks. Not all outgroups are dehumanized, and those who are, are not necessarily dehumanized to the same extent by everybody at all times. Sometimes people devalue others only in certain domains. For example, people judge outgroups as inferior especially in typically human characteristics such as intelligence (Crocker, Major, & Steele, 1998), and social competence (Glick & Fiske, 2003). Interestingly, Leyens and colleagues (2000) found that people deny outgroup members of having certain, characteristically human emotions. These so-called

21 16 second order emotions, for example jealousy and contempt, differ from primary emotions such as anger and curiosity in that they are more complex, internally caused, more invisible, and more cognitive. They occur only later in age, are less intense, and more persistent. Secondary emotions are not ascribed to animals (Leyens et al., 2000). For example, dogs can be frightened, angry, or even surprised, but one would not say that a dog admires something or feels disillusioned. The restriction of secondary emotions to be exclusive for ingroups enlarges the gap between different groups and further fosters a sense of dissimilarity between groups. If people do not feel related and affiliated with outgroup members and perceive them as dissimilar, they might have a harder time to empathize with them. To investigate whether we feel less empathy toward outgroup members and to specify what particular aspect of empathy might be impaired, we attempt to look beyond the behavioural level of empathy and to investigate by using the social neuroscientific approach. Social neuroscientific methods to measure empathy A recurrent problem in research on intergroup bias is how to measure it. People often are unwilling to reveal their prejudice and often are not even aware of them (Guglielmi, 1999). Thus research participants might not be willing or able to report possible bias in empathy towards outgroups. Moreover, conventional measures of empathy, such as self report and helping behaviour, do not allow to distinguish between the different levels of empathy (de Waal, 2008), which leaves researchers unable to make inferences about the specific mechanisms that lead to a lack in empathy. To avoid these problems, the current study uses the EEG to measure mirror neuron system activity, and to measure vicarious emotions through prefrontal alpha asymmetries. Measuring Mirror Neuron System activation. Mirror neuron system activation has been measured using several methods, including transcortical magnetic stimulation (TMS), fmri and EEG. Because the EEG is a non-

22 17 invasive, inexpensive method to measure mirror neuron activity online, we chose EEG as the main dependent measure of this study. The EEG measures mirror neuron activity by comparing electrical signals from sensorimotor neurons at rest and during the experimental conditions. At rest sensorimotor neurons spontaneously fire in synchrony, leading to large amplitude EEG oscillations in the 8-13HZ frequency band called mu band. When participants perform an action, these neurons fire asynchronously, and therefore, the power of the mu oscillations weakens. The connection between mu rhythms and mirror neuron activity was first suggested by Altschulter et al (1997). According to Altschulter the mu rhythm reflects the downstream modulation of sensorimotor neurons by cells in the premotor cortex, some of which are mirror neurons. However, when people observe actions or emotions in others, then mu rhythm reflects mirror neuron activity exclusively (Pineda, 2005). The relationship between mu rhythm and mirror neuron activity is supported by several similarities in properties between the mu rhythm and mirror neurons. First the mu rhythm is generated by activity in mirror neuron areas. Second mu rhythm is suppressed during action, but also during the observation of action (Cochin, Barthelemy, Lejeune, Roux, Martineau, 1998). Third, the mu rhythm reacts more strongly to goal directed actions than to non goal directed actions, and when the action is object oriented compared to non object oriented (Muthukumaraswamy, Johnson, McNair, 2004). Because of this overlap in location and functional properties, researchers agree that mu suppression can be used as a selective measure of mirror neuron system activity (Oberman, et al. 2006). As discussed above, mirror neurons are said to be the very basis of emotional contagion (Gallese, Ferrari, & Umilta, 2002), but the absence of mirror neuron activity does not necessarily equal the absence of empathy. Similarity and familiarity could exert their influences to a higher more cognitive level of empathy. Thus, we need a direct measure of the vicarious emotions constituting empathy.

23 18 Measuring vicarious prefrontal alpha asymmetries. A potential measure of vicarious emotions is anterior frontal asymmetries as measured by relative EEG alpha wave strength in the right vs. left prefrontal cortex. Although a relatively broad measure of general motivation, it can distinguish between positive, approach related, emotions (e.g. happiness) and negative, avoidance related emotions (e.g. sadness) (Harmon-Jones, & Allen, 1998). The earliest finding on asymmetrical organization of the prefrontal cortex comes from research on patients with brain damage to one hemisphere. For example, patients showed symptoms of depression after damage to the left hemisphere of the prefrontal cortex and mania after damage to the right hemisphere (Robinson, Kubos, Rao, & Price, 1984). These discoveries fed an extended research line on EEG alpha asymmetries in the prefrontal cortex (Fox et al., 2001, Harmon-Jones, & Allen, 1998, Jones, Field, & Davalos, 2000, Sutton & Davidson, 1997). This research consistently showed that the left prefrontal and the left anterior temporal cortex are involved in the experience and expression of positive, approach related emotions and that the right prefrontal and the right anterior temporal cortex is involved in the experience and expression of negative, avoidance related emotions (Davidson, Ekman, Saron, Senulis, & Friesen, 1990). This functional asymmetry is measured by comparing of EEG alpha band activity of both hemispheres either at rest or during different experimental conditions. This method revealed, for example, that asymmetries in alpha in the prefrontal cortex are associated with depression (Allen, Iacono, Depue, & Arbisi, 1993), a general trait like emotional style (Wheeler, Davidson, & Tomarken, 1993) and with emotional responses elicited by negative vs. positive films (Davidson, et al., 1990). When we speak about findings gained from frontal alpha asymmetries we are mainly talking about activity in the dorsolateral prefrontal cortex (Davidson, 2004). That is because

24 19 the dorsolateral prefrontal cortex is the brain structure most likely to be directly reflected in the EEG (Davidson, 2004). The dorsolateral prefrontal cortex is involved in cognitive control, and has strong connections with the orbital prefrontal cortex, a structure that assigns affective value to stimuli. Thus, the dorsolateral prefrontal cortex is essential for processing of reward and punishment. Along this line, neurophysiological research on primates suggests that reward and punishment information is passed from orbitofrontal to dorsolateral prefrontal cortex which then uses this information to guide behaviour (Wallis and Miller, 2003). Hence, although it seems that positive and negative emotions are lateralized within the prefrontal cortex, it really is the motivational component of these emotions. To distinguish the motivational aspect from the valence of emotions, Harmon-Jones and Allen, (1998) looked at anger, an emotion that has a negative valance but an approach motivational value. The negative valance should lead to left-frontal activity, whereas the approach component should lead to right-frontal activity. The researchers found that anger was associated with rightanterior activity and, thus, the left dorsolateral cortex. Hence, emotions guide our behaviour by means of approach and withdrawal motivation, motivating us to either move towards or away from stimuli. Usually, positive emotions are associated with approach motivation, for instance love leading us towards another person, while negative emotions are associated with avoidance motivation, for instance fears driving us away from another person. This motivational aspect of the experienced emotions is what we can investigate with frontal EEG asymmetries. Hence, anterior alpha asymmetries, when measured in a social setting, provide us with a measure of vicarious emotions. Moreover, since the prefrontal cortex seems to be exclusively involved in the experience and expression of emotions and not the perception of emotions (Davidson, 1994), Alpha asymmetries are a measure of vicarious emotions free of any confounds from the mere perceptions of emotions.

25 20 We used anterior alpha asymmetries as a measure for vicarious emotions, and to investigate the neural process underlying these vicarious emotions, we used EEG mu rhythm as an indicator of mirror neuron activity. We asked whether people process actions and emotional reactions of ingroup members differently than those of outgroup members. Taking together, evolutionary humans are equipped with an empathy system that allows them to navigate their social system, by understanding the emotional and cognitive states of others. However, this system evolved in a way that that makes us empathize more with similar people. Similarity and familiarity seem to even influence our most basic emphatic processes the ability to feel with others by simply simulating their emotions. In this context research findings on Prejudice, categorization and dehumanization are alarming: If we feel less similar to outgroups than to ingroups, sometimes to the degree that we see them as less human, do we even distinguish between them on a neural level? Is our mirror neuron system less sensitive to outgroup members and is empathy bounded to our ingroup? Overview This study investigated the phenomenon of bounded empathy and aimed to establish the role of the mirror neuron system in prejudice. We asked whether actions and emotional reactions of ingroup members are processed differently than those of outgroup members. We measured mirror neuron system activation and the experience of vicarious emotions with the EEG while participants saw videos of ingroup and outgroup members performing actions and expressing emotions. We predicted that the mirror neuron system would be more active when the participants observe ingroup members than when they observe outgroup members, and further, that they would feel more vicarious emotions for ingroup members than for outgroup members. In addition we expected that ingroup favouritism would be negatively correlated with, both, mirror neuron system activation and vicarious emotions in response to outgroup

26 21 members. Thus, this study suggested that the MNS is less responsive to outgroups, and that this reduction of mirror MNS activation, and the resulting lack of empathy, are at least one of the reasons for prejudice. Method Participants The original sample consisted of 30 right handed (assessed through self report) university students who were recruited from the University of Scarborough subject pool, and who participated in the study for course credit. Two participants were excluded due to a technical malfunction in the EEG system and another 7 participants had to be excluded due to excessive movement artifacts that resulted in an inability to obtain sufficient EEG data. As a result we included 21 participants in our final sample. Ten males and 11 females participated; 5 of them where white, 4 East Asian and 12 South Asian. The participants ranged in age from 18 to 23 Years (M= 18.86, SD= 1.23). Procedure Participants were told that the study s purpose was to investigate the neural underpinnings of actions and emotions. Participants read and signed an informed consent sheet and were then fitted with and electrode cap for EEG recording. EEG was recorded while the participants watched two sets of videos. The first set of videos showed a variety of ingroup and outgroup members performing a simple action. The second set of videos showed ingroup and outgroup members displaying basic emotions. After watching each set, the participants were asked to perform the action or to display the emotions respectively. After completion of this task, EEG recording stopped. To control for individual differences we, then, administered several measures related to ingroup favouritism, self-other overlap, and empathy. Finally the participants were thanked and debriefed.

27 22 Stimulus Materials The video sets of ingroup and outgroup members performing actions and expressing emotions served as the independent variable. For the purpose of this study I defined ingroup as people who share the participant s ethnic identity, and outgroup as people who do not. The first set s content was action (action block), with participants seeing and performing specified actions. Specifically, participants observed and performed the action of repeatedly grabbing a glass of water, lifting it up, drinking a small amount of the water, and putting it down. The second set (emotion block) was about emotions, with participants seeing and feeling sadness and happiness. Each set consisted of three experimental conditions - the ingroup-, the outgroup-, and the self-condition. In the outgroup condition the participant saw four different actors for each outgroup. Thus, for example, a white participant would see four different black actors each for 20 seconds followed by four different East Asian actors, and four different South Asian actors. The videos showed the actors sitting on a table in front of a white wall, either performing the action or expressing an emotion depending on set. In the ingroup condition, participants saw four different ingroup member, each for 20 seconds, acting or expressing sadness and happiness. To ensure that every participant indeed saw videos of ingroup members I presented videos depicting people with a South Asian, East Asian, Caucasian, and African ethnic background. The depicted persons were male students of the University of Toronto and, therefore, had approximately the same age but not always the same sex as the participants. Each person was displayed for twenty seconds. In order to ensure enough clean EEG data for the mu rhythm analysis, in the action set, participants observed and acted twice. Consequently we obtained 160 seconds of EEG data during the self action condition and the ingroup action condition and a total of 480 seconds during the outgroup action condition with 160 seconds for each ethnic outgroup. In the emotion conditions we obtained 80 seconds of

28 23 EEG data during the self conditions, 80 seconds during the ingroup conditions and 240 seconds of during the outgroup conditions with 80 seconds during each of the different ethnic outgroups. All ingroup and outgroup videos alternated in random order. Before participants saw the ingroup and outgroup videos, they saw 160 seconds of white noise (white noise condition). The data collected during the white noise condition was used as the baseline of mirror neuron system activation and anterior alpha asymmetry during rest. At the end of each of the video sets, the participants were asked to perform the action or display the emotions themselves (self condition). During this condition participants repeatedly grabbed the glass of water in front of them with their right hand, brought it to their mouth, and took a little sip; then they put the glass back to its former place. To ensure correct execution, they were asked to remember how the actors did the exact same action and to try to do it in the same way and same pace. In the emotion conditions participants had to either feel sad feel happy, depending on block. They were also asked to express the emotion as naturally as possible. To facilitate the experience of the emotions, participants completed an emotion induction exercise, which consisted of a series of instructions aimed to elicit vivid memories of past sad and happy events, respectively. For example, participants saw the following instruction: Please think about a situation in you past, which made you feel very sad/happy. Imagine the situation as vividly as you can. After completion of the exercise participants tried to feel the emotion for 80 seconds while they were looking at a blank computer screen. The action block always proceeded the emotion block and in each block the self conditions appeared at the end of the block so that the participants could model their performance after the videos. To ensure that participants attended the video throughout the whole session, they performed a control task during all conditions except during the white noise and self conditions. In this task, the videos stopped between 2 and 5 times and the