The Evolution of Social Pain: Understanding the Neural Network of Social Ostracism through Electroencephalography

The lack of belonging or frequent exposure to social ostracism has maladaptive psychological and physical consequences. However, little is known about the mechanisms underlying the neural processes of social ostracism. Previously, Williams (2009) showed a decrease in theta power in the frontal lobe when female participants were ostracized in a virtual chat-room. Using male and female Illinois Wesleyan college students, this study manipulated two powerful social cues (biological sex and attractiveness level) to determine their effect on prefrontal brain activity in response to social ostracism in a virtual chat-room environment. Using EEG technology, frontal theta power (4-8Hz) was measured using three cortical electrodes (the F3, F4, and Fz sites). Using a similar procedure to Williams (2009), social ostracism was elicited using a wellestablished chat-room paradigm that involved 4 phases. In the introduction, inclusion, and re-inclusion phases, participants were actively involved in the conversation, in contrast to being actively ignored during the exclusionary phase. During the exclusionary phase of the experiment, we hypothesize a significant decrease in theta power across gender and attractiveness levels in the frontal lobe. Results revealed the virtual chat-room paradigm was successful in eliciting feelings of social ostracism. Participants reported lower levels of enjoyment, F(2, 35) = 103.413, p = .000, interest, F(2, 35) = 89.89, p = .000, and participation F(2, 35) = 197.76, p = .000, as well as lines typed, F(1.564, 35) = 104.98, p = .000, during the exclusionary phase in comparison to the inclusionary phases. In addition, males reported experiencing a significantly higher degree of ostracism than females, F(1, 34) = 5.527, p = .025. Theta power showed a non-significant, F(2, 30) = 1.203, p = .180, decrease in between phases, with inclusion showing the highest overall theta power and exclusion and re-inclusion showing lower degrees of theta power. Running head: NEURAL NETWORK OF SOCIAL PAIN 3 The Evolution of Social Pain: Understanding the Neural Network of Social Ostracism through Electroencephalography Social interaction or affiliation is an instinctive behavior that all humans desire and certainly need (Leary, 2010). Unfortunately, the vast majority of adolescents and adults have experienced some sort of rejection or social ostracism (Leary, 2010). This type of behavior induces social pain, while simultaneously denying the social need for acceptance (Leary, 2010). Two contributing factors that influence individuals’ motivation to interact and socialize include the particular sex and attractiveness level of the individual (Stroud, Salovey, & Epel, 2002). Although the need to belong is crucial for psychological homeostasis, the lack of belonging or frequent exclusive experiences have been shown to cause maladaptive psychological and physical consequences. To date, there has been little research examining these contributing factors and how they influence reactions to social ostracism (Eisenberger, 2006). This study examines whether attractiveness and biological sex contribute to individuals’ responses to social ostracism as measured by alterations in neural activity. It is evolutionarily adaptive to possess a protective social neural alarm system that alerts an individual to the possibility of being ostracized, while relaying crucial information to specific structures responsible for providing an appropriate response to eliminate or minimize the possible negative psychological implications of being ostracized (Lorenz, Minoshima, & Casey, 2003). By examining the psychological effects of ostracism, and the environmental cues that affect its severity, researchers can better understand the specific structures involved and their overall contribution to an appropriate response. Psychological Effects of Social Ostracism Running head: NEURAL NETWORK OF SOCIAL PAIN 4 Although people differ in how they respond and deal with rejection, it is clear that social ostracism is a painful and sometimes hostile experience that can impair individuals’ emotional well-being, self-esteem, and social behavior (Ford & Collins, 2010). Being excluded has been shown to reduce one’s sensitivity to physical pain as well as one’s empathy towards an individual who has suffered some sort of physical or social injury (DeWall, & Baumeister, 2006). Instead of trying to change social routines or mannerisms to increase chances of social acceptance, most excluded individuals begin to socially malfunction by adopting self-defeating behaviors such as aggression, failure to self-regulate, decrease in intellectual functioning, and increases in risk taking behavior (DeWall, & Baumeister, 2006). Self regulation or self control is the ability for individuals to actively change specific behaviors, thoughts, and emotions to minimize pain and ensure positive outcomes (Krug, & Carter, 2010). If this regulatory system is not maintained through reliable social support groups, excluded individuals have trouble reacting to social ostracism in an effective way (Heckel, & Shumaker, 2001). Being excluded from a peer group or intimate relationship not only causes immense pain, but also elicits aggression that could be used to harm innocent bystanders. This aggression has been displayed in several school shootings such as Columbine and Virginia Tech, in which the perpetrators were both highly aggressive individuals who were rejected by fellow peers (Heckel, & Shumaker, 2001). Social ostracism disrupts self-control by preventing individuals from developing adequate personal and social skills necessary for inclusion eventually decreasing one’s self-esteem, and increasing the possibility of psychological problems (Leary, 2010). High self-esteem correlates with emotional well-being; whereas low self-esteem has been shown to contribute to symptoms of anxiety, depression, and Running head: NEURAL NETWORK OF SOCIAL PAIN 5 conformity (Eisenberger, &Lieberman, 2004). In order to induce survival, humans have evolved to instinctively require the regulatory processes of self-esteem on the basis that the creation and maintenance of self-esteem is heavily dependent on the evaluation of interpersonal relationships (Williams, & Carter-Sowell, 2009). Self-esteem acts as a regulatory process by indirectly representing social connectedness through the manipulation of psychological health (Eisenberger, &Lieberman, 2004). Socially ostracized individuals experience increased negative self-feelings and a reduction in selfesteem that could possibly constrict relationship enhancement processes (Eisenberger, &Lieberman, 2004). In a study measuring psychological responses to interpersonal rejection, individuals with low trait self-esteem compared to individuals with high trait self-esteem responded to rejection pessimistically, exhibiting increased self-blaming attributions and aggression towards the rejecter (Ford, & Collins, 2010). In addition, individuals with a high sensitivity to rejection and a low self-esteem may try to alleviate the rejection or social ostracism by conforming to a group’s certain set of unfamiliar rules or norms (Romero-Canyas, Downey, Reddy, Rodriguez, & Cavanaugh et al., 2010). Unknowingly, individuals may adopt new personal goals inevitably inducing maladaptive behaviors that make individuals susceptible to manipulation or abuse (Romero-Canyas et al., 2010). In addition to recognizing social ostracism’s psychological effects, it is important to examine important social cues and their effect on influencing the severity of ostracism. Sex Differences in Social Ostracism Social interaction is based on the premise that human thought, emotion, and behavior is molded and institutionalized by human interaction based on characteristics including biological sex, age, race socioeconomic status and attractiveness level Running head: NEURAL NETWORK OF SOCIAL PAIN 6 (Eisenberger, & Lieberman, 2004). These differences serve as stereotypical moderators for personal and social evaluations that impact social interaction, as well as social ostracism (Ritts, Patterson, & Tubbs, 1992). Starting from birth, males and females are culturally categorized into socialized gender roles that condition individuals to follow a socially acceptable set of rules (Wester, Vogel, Pressly, & Heesacker, 2002). The interpretation and reaction to social ostracism is highly influenced by these normative guidelines (Wester, Vogel, Pressly, & Heesacker, 2002). Although previous literature has shown no moderation in self-reported distress levels with respect to sex differences during ostracism (Williams, & Sommer, 1997), recent brain imaging studies have revealed significant sex differences in the cortical electrophysiological processing of emotional stimuli (Kemp, Silberstein, Armstrong, & Nathan, 2004).By showing differences in the neural processing of emotion, it is possible males and females may demonstrate neural differences in processing ostracism, while failing to show any selfreported psychological differences. Numerous studies have documented sex differences in the neural processing of emotion as well as threat detection, facial processing, reward/outcome processing, and nonverbal interpretation. The differences in processing these social cues can be seen by different brain activations and interpersonal sensitivity to specific emotional stimuli (Hall & Mast, 2008). It appears females are predisposed to process and react to emotionallyrelevant stimuli due to their heightened response and unique bilateral activations of several neural structures that include the insular, prefrontal and parietal cortices, bilateral visual processing areas, thalamic nuclei, amygdala, caudate, putamen, and the postcentral and parahippocampal gyri (Kemp, Silberstein, Armstrong, & Nathan, 2004). Furthermore, George et al. (1996), observed increased activity for females in the bilateral Running head: NEURAL NETWORK OF SOCIAL PAIN 7 anterior cingulate, left medial prefrontal cortex, left insula, and thalamus compared to males who failed to activate any of the prefrontal or anterior cingulate cortex (Kemp, Silberstein, Armstrong, & Nathan, 2004). This increase in activation is the underlying premise of Hankin and Abramson’s (2001) cognitive vulnerability-transactional stress theory, which highlights the overrepresentation of females over thirteen diagnosed with depression (Kemp, Silberstein, Armstrong, & Nathan, 2004). In addition to differences in neural processing of emotional stimuli, researchers have also found significant differences in the detection of nonverbal social cues such as facial expressions, body movements, postures, and tone of voice (Hall & Mast, 2008). Previous literature highlights female’s enhanced ability to accurately judge a profile of personality, as well as remember dynamic cues such as shrugging, smiling, gazing, nodding, licking lips, and touching hair compared to males (Hall & Mast, 2008). By excelling in the detection, interpretation, and memory of emotional social cues, females may preferentially respond to social ostracism’s negative effects. In a study measuring picture processing, females were more likely to respond to aversive stimuli with greater defensive reactivity than males, highlighting female’s susceptibility to social ostracism (Bradley, Codispoti, Sabatinelli, & Lang, 2001). Although currently there are no sex differences in psychological responses to ostracism, males and females may differ in how they detect and neurologically process ostracism. To date, there has been little research investigating biological differences in detecting and neurologically processing ostracism in a virtual chat-room paradigm. Combining females’ hyperactivity of the limbic system, and advanced ability in detecting nonverbal social cues, it is possible sex differences may influence individuals’ detection Running head: NEURAL NETWORK OF SOCIAL PAIN 8 of social ostracism by detecting and neurologically processing emotional stimuli such as ostracism differentially. Attractiveness Levels in Social Ostracism Similar to biological sex, differences in attractiveness might also influence social interaction by allowing individuals to positively evaluate a significant other in order to determine their desirability to approach and interact or to protect and defend (Ritts, Patterson, & Tubbs, 1992). In today’s society, being physically attractive is not only advantageous, but also a crucial characteristic that influences social interaction. Although physical attractiveness is a subjective and abstract concept, the majority of individuals, both male and female agree, on what is physically attractive (Franzoi, & Herzog, 1987). Researchers have also observed attractive students being stereotypically rated friendlier, more attentive, more popular, smarter, and more outgoing (Ritts, Patterson, & Tubbs, 1992). It appears “what is beautiful is good” (Dion, Berscheid, & Walster, 1972, 675). These characteristics not only help foster social relationships, but more importantly represent status, power, and success. In a study investigating jealously, a social characteristic involved in social relationships, Harmon-Jones, Peterson, and Harris (2009) observed increased cortical activation in the left frontal region when participants were exposed to sexually desired confederates during a modified version of the cyberball task. Highlighting the power of environmental cues such as desirability, this study supports the claim that specific environmental influences can alter biological and psychological responses to ostracism. Acting as a major contributor to desirability, attractiveness levels also have the capability to influence individuals’ stress response, by altering perception and reaction to the social ostracism stimuli. In addition, an experiment measuring attractiveness and its effect on social interactions, found that when given the opportunity Running head: NEURAL NETWORK OF SOCIAL PAIN 9 to converse with attractive females, males generally interacted less with the females and more with the males for fear of rejection (Reis, Wheeler, Spiegel, Kernis, Nezlek, & Perri, 1982). Attractiveness is not only a determining factor in whether to socialize with an individual or not, but also a contributing force to the severity of rejection and its tendency to elicit maladaptive behaviors. A Common Neural Network Using brain scanning techniques such as functional magnetic resonance imaging, a common neural network between physical and social pain has been found (Eisenberger, Lieberman, & Williams, 2003). Although social and physical pain may cause similar psychological trauma, perception and response to each particular pain vary greatly. Physical pain is any sort of distressing or unpleasant experience caused by actual physical tissue damage, whereas social pain is any distressing or painful experience in the face of psychological distance or exclusion by family, friends, or social groups (Eisenberger, & Lieberman, 2004). This adaptive overlap adopts the understood and accepted social attachment system evolved in mammalian species to prevent social separation inducing optimal survival (Eisenberger & Lieberman, 2004). In a study conducted by Eisenberger, Lieberman, and Williams (2003), participants who were intentionally excluded from a virtual ball tossing game demonstrated similar neural activation in brain structures that regulate physical pain. Furthermore, chronic social isolation through exclusion or marginalization may create long-term consequences on the physiological responses individuals have in social situations by increasing the levels of stress hormone cortisol via the neuroendocrine system (Ford, & Collins, 2010). In a study conducted by Ford and Collins (2010), researchers found that even minuscule cues of possible social rejection or exclusion were sufficient to evoke a full physiological stress response through greater Running head: NEURAL NETWORK OF SOCIAL PAIN 10 cortisol reactivity. This response impairs individuals’ social skills by quickly initiating defensive behaviors in the presence of possible threat or rejection (Ford, & Collins, 2010). Interaction has become so crucial for survival in today’s society that over time specific social experiences such as inclusion and exclusion have become relevant causing the need for humans to evolve and adopt a neural network that regulates and controls these experiences. Following the social attachment system formulated by psychoanalyst John Bowlby, specific social experiences are controlled by the same neural structures as the physical pain system to serve as a strong foundation in the protection and regulation of the evolved attachment system seen in humans (Lieberman, & Eisenberger, 2006). This common neural alarm system detects, interprets, and reacts, to social stimuli to ensure safety and emotional well-being by activating and disrupting neural activity in specific brain structures responsible for the regulation of pain. Structures Involved in Regulation The neural network of social pain consists of brain structures such as the dorsal anterior cingulate cortex (dACC), right ventral prefrontal cortex (RVPFC), inferior frontal gyrus, posterior superior temporal sulcus (pSTS), temporo-parietal junction (TPJ), amygdala, and anterior insula (Sebastian, Viding, Williams, & Blakemore, 2010). Specifically the dACC has been shown to be influenced by the right ventral prefrontal cortex by disrupting the dACC’s neural alarm system (Eisenberger, Jarcho, Lieberman, & Naliboff, 2006). In a study using fMRI images to determine when specific brain structures like the dACC and RVPFC are activated, researchers found that the dACC was more activated when participants were excluded and was inversely correlated with the RVPFC in self-reported distress (Eisenberger, Lieberman, & Williams, 2003). These findings parallel the results recorded by these two structures when testing physical pain. Running head: NEURAL NETWORK OF SOCIAL PAIN 11 This helps to answer why humans demonstrate an anxious attachment style when suffering from chronic pain disorders, as well as reporting lower levels of physical pain by increased social support during painful experiences such as cancer treatment and surgery (Eisenberger, & Lieberman, 2004). Dorsal Anterior Cingulate Cortex The dACC regulates and resolves conflict that endangers or threatens individuals’ automatic or goal-directed behavior by monitoring the environment for possible threats or discrepancies and alerting prefrontal regions if a violation occurs (Eisenberger, & Lieberman, 2004). For example, in the Stroop task, a task that measures discrepancy detection using colors, researchers found that participants produced activation in neighboring and even overlapping regions of the dACC when a violation of the norm was presented (Eisenberger, & Lieberman, 2004). Furthermore, individuals with low social support showed greater activation in the dACC compared to controls when participating in a cyberball task (Masten, & Eisenberger, 2009). In this task, participants interacted in a computerized virtual ball tossing game designed to include participants in one stage and then exclude them in another to determine the neural activations caused by this specific type of ostracism (Williams, & Carter-Sowell, 2009). During the exclusionary stage of this task, participants’ demonstrated activation in the dACC compared to when included (DeWall, & Baumeister, 2006). These studies demonstrate not only dACC’s important role in monitoring the environment, an obvious evolutionary trait, but also the crucial role in creating a common computational basis for both physical and social pain. In studies measuring physical and social pain, the dACC has shown similar results, indicating its broad role in pain regulation (DeWall, & Baumeister, 2006). During physical pain, nociceptors send electrical impulses to the brain causing specific neurotransmitters and Running head: NEURAL NETWORK OF SOCIAL PAIN 12 brain structures to become activated. Researchers concluded that the dACC was responsible for regulating the distressing and dreadful sensitivity to physical pain by demonstrating greater activation in high pain sensitivity participants (Masten, & Eisenberger, 2009). Similar to the regulatory processes of physical pain, the dACC monitors the environment for threatening stimuli such as social ostracism and transfers this information to the brain regions responsible for interpretation. The Ventral Medial Prefrontal Cortex After the dorsal anterior cingulate cortex becomes activated it alerts prefrontal regions like the right ventral medial prefrontal cortex (RVMPFC) to create an appropriate behavioral response (Eisenberger, & Lieberman, 2004). The RVMPFC, a structure responsible for coordinating complex behaviors, contributes to self-referential processing that incorporates and interprets information about the environment, the self, and others (Tesink, Buitelaar, Petersson, Gaag, Kan et al., 2009). Individuals with lesions to this area of the cortex show deficiencies in obeying normal social cues, impulse control, as well as conducting appropriate responses to social cues (Tesink et al., 2009). Similar to individuals with autism spectrum disorders, individuals with VMPFC lesions have trouble interpreting environmental stimuli, as well as maintaining normal emotional and social conduct (Dimitrov, Phipps, Zahn, & Grafman, 1999). Although these brain structures work in conjunction, it is important to note that there exists a negative relationship between activations. The RVMPFC has shown increased activation as a result from decreased dACC activation. This strong negative relationship could perhaps demonstrate the RVMPFC’s responsibility as a self-regulatory structure responsible for disrupting dACC activity (Eisenberger, & Lieberman, 2004). It appears the RVMPFC functions as a physical and social pain mediator by reducing the distressing effects Running head: NEURAL NETWORK OF SOCIAL PAIN 13 associated with it. This can be seen by such experiments as Zhang, Tang, Yuan, & Jia (1997), in which the sensation of pain is reduced through increased stimulation and activation of the RVPFC. In a study conducted by Kross, Egner, Ochsner, Hirsch, & Downey (2007) using fMRI technology, researchers found that high rejection sensitivity individuals failed to show any left prefrontal cortex activation compared to low rejection sensitivity individuals. This study supports the prefrontal cortex’s role in top down cognitive control and interpretation of somatic information recognized by the amygdala (Kross et al., 2007). The Amygdala Similar to the dACC, this negative relationship has also been observed between the RVMPFC and the amygdala (Masten, & Eisenberger, 2009). The amygdala, a structure responsible for aiding in threat detection is decreased with increased activation of the RVMPFC (Masten, & Eisenberger, 2009). This structure is understood to be involved with social behavior and emotion, specifically recognizing and controlling emotional responses to facial expressions (Yang, Menon, Eliez, Blasey, White, Reid, Gotlib, & Reiss, 2002). The recognition of broad emotional expression may provide critical information in solving or reacting to difficult social situations such as ostracism. Recognizing broad and fearful facial expressions, the amygdala plays an important communicative role in threat detection and face processing (Morris, Friston, Buchel, Frith, Young, Calder, & Dolan, 1998). This structure evaluates the emotional significance of stimuli such as complex judgments of trusting other individuals (Adolphs, 2003). Participants with bilateral amygdala damage have shown abnormalities in their judgments of trustworthy people, rating individuals more trustworthy and approachable than normal viewers (Adolphs, 2003). By rapidly processing ambiguous emotional and threatening Running head: NEURAL NETWORK OF SOCIAL PAIN 14 stimuli, the amygdala plays an important role in linking perceptual representations to cognition, influencing appropriate behavioral responses (Adolphs, 2001). Once activated, the amygdala tags somatic information gathered from the environment and transfers this vital information to the RVMPFC for interpretation (Bechara, Damasio, & Damasio, 2003). Purpose of Study Rather than using traditional functional magnetic resonance images (fMRI) to observe the neural network of pain modulation, this study adopts an innovative technique of electroencephalographic (EEG) recordings to examine theta rhythm. Due to the large emphasis on fMRI research and the limited use of EEG recordings, it is important to investigate whether each pair of these methods complement or contradict each other. In addition, fMRI studies rely on hypothetical scenarios that place the participant in a nonrealistic supine body position (Harmon-Jones, Peterson, & Harris, 2009). These two characteristics present limitations capable of altering results. For example, supine body positions during an fMRI have been shown to reduce the neural response to anger (Harmon-Jones, & Peterson, 2009). Using real-life scenarios and testing in an upright body position, EEG recordings offer an alternative to these limitations and offer a different perspective on neural activity. This noninvasive measure of electrical brain activity measures several brain wave frequencies such as theta (4-8 Hz), alpha (8-12 Hz), Beta (12-30), and Gamma (30-100+ Hz) (Nunez, & Srinivasan, 1981, 78). This study measures theta waves, specifically differences in amplitude, because it appears to be involved in the mediation of emotional processing such as empathy for pain in the anterior cingulate cortex, prefrontal cortex and insula (Mu, Fan, Mao, & Han, 2008). In a study measuring empathy for pain, participants showed increased theta event-related Running head: NEURAL NETWORK OF SOCIAL PAIN 15 synchronization in the presence of painful stimuli highlighting theta’s waves possible role in affective processing of empathy for pain (Mu, Fan, Mao, & Han, 2008). By utilizing theta waves’ emotional characteristics in a relevant environment, a better understanding about the psychological effects of social interaction in a virtual chat-room can be investigated. Using a virtual chat room paradigm to elicit cyber-ostracism is not only appropriate, but also extremely relevant as a result of today’s emphasis on computerized communication such as on-line dating networks, as well as Twitter and Facebook. As social interaction becomes more virtualized, the importance and necessity for humans to receive immense social nurturing and adequate social inclusion has been supported by showing the serious mental and physical health concerns for those who have not had this need fully satisfied. Understanding how the brain perceives and reacts to social ostracism in a modern virtual environment will help clinicians create practical intervention programs, as well as offer a greater understanding as to how humans have evolved into a social species. As societies continue to grow and evolve placing greater importance on social instincts, it is crucial to understand the neural structures involved in the formation and denial of relationships. Due to previous research highlighting social ostracism’s detrimental effects on individual’s physiological and psychological well-being, the current study purposely ignores subjects in a specific part of the simulated chat room conversation to observe the unique activations of the social neural alarm system. Understanding social interaction is highly influenced by physical and environmental cues, sex differences and attractiveness levels were manipulated to determine if any significant differences arose in how participants perceived and reacted to social rejection. During the exclusionary phase of the experiment, we hypothesize a significant decrease Running head: NEURAL NETWORK OF SOCIAL PAIN 16 in theta power causing a de-synchronization of theta activity across gender and attractiveness levels in the frontal lobe for college students during a virtual chat room study.