Evolutionary Behavioral Sciences © 2014 American Psychological Association 2014, Vol. 8, No. 4, 235Ð243 2330-2925/14/$12.00 http://dx.doi.org/10.1037/ebs0000024 Recontextualizing the Behavioral Within Psychoneuroimmunology

Jason A. Clark Daniel M. T. Fessler University of Osnabrueck University of California, Los Angeles

We believe that the concept of the behavioral immune system (BIS) picks out an important set of phenomena, namely, the relationships between the immune system and disease-avoidant psychology. However, our enthusiasm is tempered by the recognition that (a) there are unresolved ambiguities in the BIS concept, which has been used in a variety of (sometimes inconsistent) ways; (b) many types of phenomena it has been used to identify are already well characterized in other disciplines that have received inadequate attention by BIS researchers; and that (c) these disciplines offer a broader contextualization of the phenomena. We argue that the BIS concept should be recon- textualized within and integrated with such research programs. More specifically, we believe that the BIS should be set within the framework of psychoneuroimmunology. We consider several ways in which the BIS might be differentiated from psychoneu- roimmunology, arguing that none of these clearly sets the BIS apart. These include (a) the notion of the BIS a purely defensive, prophylactic response to disease threats; (b) the BIS as concerned primarily with -related responses; (c) the BIS’s role in generating large-scale effects of pathogens on social structure; (d) the BIS as a primarily psychological, rather than a mechanistic, account of psycho-immune inter- actions; and (e) the BIS as a specifically evolutionary, rather than descriptive, approach to disease-avoidant psychology and behavior. We believe that centering BIS research within psychoneuroimmunology will better capture the value and novelty of BIS research, more accurately reflect the intentions of BIS researchers, and better advance their aims.

Keywords: behavioral immune system, psychoneuroimmunology, ecoimmunology, disgust

We believe that the concept of the behavioral BIS concept and it has been used in a variety of immune system (BIS) picks out an important set (sometimes inconsistent) ways, (b) many types of phenomena, namely, the relationships be- of phenomena it has been used to identify are tween the immune system and psychological already well characterized in other disciplines mechanisms that manage the threat of infectious that have received inadequate attention by BIS disease. We also believe that research con- researchers, and that (c) these disciplines offer a ducted using the concept makes valuable and broader theoretical contextualization of the phe- novel contributions to the larger field. However, nomena. We argue that the BIS concept should our enthusiasm is tempered by the recognition be recontextualized within and integrated with that (a) there are unresolved ambiguities in the

This document is copyrighted by the American Psychological Association or one of its allied publishers. such research programs. More specifically, we

This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. believe that the BIS should be set within the framework of psychoneuroimmunology (PNI). While neuroimmunology encompasses both Jason A. Clark, Institute of Cognitive Science, University peripheral and central nervous systems, and of Osnabrueck; Daniel M. T. Fessler, UCLA Center for Behavior Evolution and Culture, Anthropology Department, psychoimmunology focuses on the interactions University of California, Los Angeles. between specifically psychological variables Correspondence concerning this article should be ad- and immune function, PNI highlights the con- dressed to Jason A. Clark, Institute of Cognitive Science, tributions of the central nervous system, and the University of Osnabrueck, 28 Albrechtstrasse #417, 49069 Osnabrueck, Germany. E-mail: jasonanthonyclark@gmail ways in which the brain instantiates psycholog- .com ical constructs, and mediates interactions be-

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tween psychological variables and the immune The BIS As Disease Prophylaxis system. Its object of study is the psychoneuro- immune system (PNIS). Work in PNI was ini- As suggested by the term itself, the BIS en- tially largely restricted to how mental states can compasses the specifically behavioral compo- influence physical health outcomes, addressing nents of disease avoidance. There is a need for comparatively simple effects of peripheral im- a concept to refer specifically to the behavioral mune responses on psychology, and largely aspects of disease avoidance (i.e., an ethology concerned with “gross” nonspecific changes in of disease avoidance), especially in comparative both psychology and immune responses. How- studies under naturalistic conditions where the ever, especially in the last 15 years or so, the ability to measure and manipulate disease- field has grown enormously, and there is an related variables is limited (Nunn & Altizer, increasing recognition of the breadth and com- 2006). Some work that is frequently cited by plexity of the interactions among the immune BIS researchers falls into such a category (Hart, system and quite high-level psychological vari- 1990, 2011). However, as Schaller notes when ables, including the fact that such effects on introducing the term, the BIS would better be cognition can be highly specific, and not limited called the “psychological immune system,” but to general parameters. For example, the im- because that term was already in use, referring mune system has been linked to the cognitive, to a distinct set of processes (Gilbert, Pinel, affective, and behavioral aspects of a range of Wilson, Blumberg, & Wheatley, 1998), psychiatric disorders, either as a cause, effect, Schaller chose “behavioral” (Schaller, 2006,p. or both, including, for example, depression 97). Hence, the term “behavioral” is not re- (Janssen, Caniato, Verster, & Baune, 2010; stricted to ethology, but should be taken as Leonard & Myint, 2009; Müller, 2014; Schiep- referring to psychology more generally, as ers et al., 2005; Tanaka et al., 2012), and schizo- when psychology is called “behavioral sci- phrenia (Debnath & Venkatasubramanian, ence.” For example, Schaller and colleagues 2013; Mondelli & Howes, 2014; Müller & Dur- (Schaller, 2006; Schaller & Duncan, 2007; sun, 2011; Müller, 2014). As we shall see, work Schaller & Park, 2011) define the BIS as “a by BIS theorists adds to the catalogue of such suite of psychological mechanisms that (a) de- effects. tect cues connoting the presence of infectious While it is true that once we conceptualize pathogens in the immediate environment, (b) the BIS within PNI, the novelty of the contri- trigger disease-relevant emotional and cognitive butions made by BIS researchers will become responses, and thus (c) facilitate behavioral clearer, we nevertheless caution that we should avoid putting too much weight on the BIS con- avoidance of pathogen infection” (Schaller & cept, which should be seen more as a rallying Park, 2011, p. 99). point for multidisciplinary interaction, than as The term “behavioral” has another connota- identifying a novel system or discipline, a fea- tion in the BIS literature, namely as referring to ture that it shares with similar disciplines that psychological and behavioral defenses that have emerged alongside it, such as “ecoimmu- serve to avoid disease in the first place, short of nology,” discussed later. We consider several activating the physiological mechanisms of the ways in which the BIS might be differentiated classical immune system (CIS). This is perhaps from PNI, arguing that none of these clearly sets the primary way in which the BIS is distin- This document is copyrighted by the American Psychological Association or one of its allied publishers. the BIS apart. These include (a) the notion of guished from related immunological concepts. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. the BIS a purely defensive, prophylactic re- The BIS is nearly always described as providing sponse to disease threats; (b) the BIS as con- a first-line prophylactic defense against disease, cerned primarily with disgust-related responses; and this is presented as one of its primary ad- (c) the BIS’s role in generating large-scale ef- vantages, the idea being that whereas the CIS is fects of pathogens on social structure; (d) the merely reactive, engaged only once pathogens BIS as a primarily psychological, rather than a have been contacted, the BIS serves to avoid the mechanistic, account of psycho-immune inter- costs associated with CIS reactions to active actions; and (e) the BIS as a specifically evolu- infections. For example, Neuberg, Kenrick, and tionary, rather than descriptive, approach to dis- Schaller (2011) define the BIS as “a system ease-avoidant psychology and behavior. designed not to fight pathogens postinfection RECONTEXTUALIZING THE BEHAVIORAL IMMUNE SYSTEM 237

but rather to avoid infection in the first place” (recent illness) increased activation of the BIS in (p. 1045). the form of attention to and avoidance of per- However, this approach to differentiating the ceived disease threats (disfigured individuals). BIS is problematic. First, a large body of work Stevenson et al. (2012) found that activation of the tells us that the relationships between our psy- BIS via induction of disgust increased body tem- chology and immune function also promote a perature, and also up-regulated oral immune variety of psychological in response not only to markers. More broadly, Rubio-Godoy et al. potential infection, but also to active infection, (2007) point to a number of interconnections be- potentially serving a number of functions. For tween the CIS and psychological disease avoid- example, “sickness behavior” in response to ance via the shared use of serotonin systems. Fi- infection (and its psychological correlates) have nally, Macmurray et al. (2014) present evidence been hypothesized to function to facilitate re- that variants in regulatory genes are covery, conserve resources, avoid further infec- likely to be pleiotropically linked with behavioral tion, prevent transfer to other group members, and psychological responses via the action of cy- and avoid conflict in a weakened state (Adel- tokines on the central nervous system. They stud- man & Martin, 2009; Dantzer & Kelley, 2007; ied the gamma-interferon (IFNG) ϩ874 A-al- Maes et al., 2012). In line with this, some BIS lele, which is known to down-regulate researchers have incorporated responses to ac- serotonergic activity, thereby allowing it to af- tive infection into their definition of the BIS. fect behavioral and psychological variables. For example, Fincher and Thornhill (2012) de- The IFNG ϩ874 A-allele is associated with fine the BIS as including not only antiparasite greater susceptibility to a variety of infectious psychology, but also “psychology and behavior diseases, but also confers protection against that manages infectious diseases when they oc- pregnancy loss, thereby potentially trading off cur” (p. 62). Sickness behavior has been a cen- greater reproductive success against increased tral topic in PNI. disease risk. The authors hypothesized that such Another problem with interpreting the BIS as increased disease risk may be offset by psycho- an exclusively prophylactic system is the extent logical and behavioral tendencies that protect to which we can draw a clear distinction be- against infection, determined by genetic factors tween the BIS and the CIS, and the degree to pleiotropically linked to the IFNG ϩ874 A-al- which this reflects a difference between preven- lele. They found that the IFNG ϩ874 A-allele tative versus reactive responses. There is a large was associated with increased harm avoidance, body of work in PNI documenting the deep and decreased exploratory excitability and ex- intertwining of psychological variables and the traversion. While noting that their results pres- CIS, much of which has been neglected by BIS ent some support for BIS theories, Macmurray theorists. Furthermore, even the work of some et al. specifically criticize the notion that the BIS theorists calls into question the tenability of CIS is merely reactive, suggesting instead that such a distinction. For example, Schaller claims the CIS also mediates proactive responses, both that the BIS is “an integrated set of psycholog- traditional physiological responses, and psycho- ical mechanisms that facilitate prophylactic be- logical defenses. havioral defense against pathogens...Previ- Hence, the BIS and CIS are deeply inter- ously unexplored, however, is the intriguing twined in both directions: the BIS can activate possibility that these processes might also have the CIS, and the CIS itself is involved in mod- This document is copyrighted by the American Psychological Association or one of its allied publishers. an influence on the real immune system” ifying psychological responses as an integrated This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. (Schaller et al., 2010, p. 649). Schaller et al. part of such responses, rather than simply being (2010) demonstrate that simple visual exposure a separate line of defense that is only activated to signs of illness primes the CIS to deal with once infection occurs. All of this suggests that, potential infection. While it is true that the while there may be instances of psychological particular effects found by Schaller et al. were defenses that neither activate, nor are activated previously unexplored, the notion that such psy- by the CIS, the BIS and CIS may not be merely cho-immune linkages are likely to occur has two distinct but highly interactive systems. In- long been suggested by PNI. stead, given the depth of immune-psychology Others have found similar effects. Miller and interactions and the degree to which these sys- Maner (2011) found that activation of the CIS tems are intertwined, it is unlikely that prophy- 238 CLARK AND FESSLER

lactic cognition or behavior can be cleanly sep- erson et al., 2004). Immune correlates have also arated from activation of the immune system been found for fear, anxiety, and stress (Denson proper. This is precisely the picture presented et al., 2009; Glaser & Kiecolt-Glaser, 2005; by PNI. Indeed, results such as these, including Segerstrom & Miller, 2004), and anger and ag- Schaller and colleagues’ own work, are, in ef- gression (Chrousos, 2009; Moons, Eisenberger, fect, examples of PNI. & Taylor, 2010). Hence, the preparatory role of psycho-immune responses in emotions is not The BIS and Disgust restricted to disgust. Finally, in humans at least, disgust has arguably acquired functions that Disgust has perhaps been the primary disease- have nothing to do with disease avoidance, such avoidant psychological response studied by BIS as the avoidance of suboptimal mates (sexual theorists, and is hypothesized to underlie many of disgust), and the rejection of norm violators the individual- and social-level responses associ- (moral disgust; Fessler & Navarrete, 2004; ated with the BIS (Clay et al., 2012; Duncan & Borg, Lieberman, & Kiehl, 2008; Rozin et al., Schaller, 2009; Inbar et al., 2009, 2012; Prokop, 2010; Tybur et al., 2009, 2013). This further Usak, & Fanoviová, 2010; Terrizzi et al., 2013; raises the possibility that immune system reac- Tybur et al., 2010). Disgust, in turn, has received tions originally designed purely to fight infec- more attention in the BIS literature than in other tion, (e.g., immune-induced nausea), may have related literatures, and BIS theorists have consid- been co-opted for functions unrelated to dis- erably advanced our understanding of disgust in ease avoidance, for example, the use of im- ways that enrich the aims of related literatures. mune-induced nausea to activate the cogni- Many of these authors have suggested that the BIS tive mechanisms underlying disgust in the bears a special relationship to disgust, so perhaps service of mate choice or norm enforcement we should construe the BIS as emphasizing dis- (Clark & Fessler, 2014). All of this should gust-specific elements of disease avoidance. There provide caution against postulating too close is general agreement that one of the primary an identification the BIS with disgust-related evolved functions of disgust is to provide protec- responses. tion against pathogens, so a focus on disgust in BIS research makes eminent sense. The Effects of Pathogens However, we caution against postulating too on Social Structure: The BIS and exclusive a relationship between disgust and the Ecoimmunology (EI) BIS. First, not all disease-avoidant psychologi- cal responses are mediated by disgust, but also Another area that has received considerable appear to involve fear, or other related emo- attention from BIS researchers is the effects of tions. Indeed, it appears that in other animals parasites on large-scale social structure and be- disgust is restricted to the avoidance of orally haviors, and such theorists have provided novel incorporated pathogens, and that it is only in arguments concerning such effects. For exam- humans that disgust mediates reactions to ple, Fincher and Thornhill (2012) have argued pathogens that are conveyed via nonoral routes that parasite prevalence affects a wide range of (e.g., insects and bodily fluids), whereas avoid- social variables, such as collectivism versus in- ance of such pathogens in other animals is me- dividualism, and the psychological mechanisms diated via different, fear-like reactions (Kava- that help to mediate them, for example, person- This document is copyrighted by the American Psychological Association or one of its allied publishers. liers et al., 2003, 2005; Clark & Fessler, 2014). ality traits such as extraversion and introver- This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. Second, while disgust may have a special con- sion. While Fincher and Thornhill cite the BIS nection to disease and immune variables in vir- concept, here the BIS is seen as one mediator of tue of its primary functions in pathogen avoid- the broader effects of pathogens on social struc- ance, it is worth emphasizing (to a greater ture and intergroup relations proper, which they extent than the BIS literature has) that PNI has call the Parasite-Stress Theory of Sociality identified immune correlates of many emotions. (PSTS), and the concept itself does not play a For example, shame involves immune re- prominent role in their articulation of these dy- sponses that have been hypothesized to derive namics. However, as they note, the PSTS and from more basic ancestral responses in response the BIS concept overlap with the aims of an- to loss and injury in violent encounters (Dick- other discipline, EI, which emerged at about the RECONTEXTUALIZING THE BEHAVIORAL IMMUNE SYSTEM 239

same time (Martin et al., 2011; Viney & Riley, leagues in the context of EI (Cremer et al., 2014). EI represents the synthesis of results 2007; Cremer & Sixt, 2009). Cremer at al. con- from many subdisciplines, and advocates a sider the notion of a social immune system in cross-level, cross-disciplinary methodology. the context of insect colonies that form super- More specifically, EI theorists emphasize (a) the organisms (e.g., ants and termites), examining effects of environmental factors under natural both prophylactic and reactive responses to dis- conditions, (b) shifting from primarily genetic ease, at the level of both the individual and the approaches to whole-organism approaches, (c) colony. Cremer at al. focus primarily on draw- developmental and other epigenetic factors, (d) ing analogies between such colonies and indi- variability in immune responses at the level of vidual immune systems in vertebrates (e.g., individual differences, as well as (d) variability comparisons of specialized antiparasite workers because of ecological factors such as latitude, in a colony and T-cells in the immune system of temperature, and season. EI especially empha- individual vertebrates) thereby demonstrating sizes trade-offs between immune responses and common principles underlying various branches other selective pressures, such as growth, repro- of . Cremer et al. do not devote duction, and social status, and how these affect much attention to analogies between the social variation in immunological strategies at both behavior of insect colonies and the social be- individual and social levels, stressing that that haviors of other species. However, such insights immune responses must be both up- and down- are also applicable to social-level responses of regulated in response to such pressures. As many species, humans in particular, a point Trotter et al. (2011) put it, “Organisms evolve articulated by Cotter and Kilner (2010). Never- optimal immunity...notmaximal immunity” theless, while the BIS has been employed in (p. 41). EI is contrasted in these respects with accounts of social-level phenomena, we believe traditional immunology, which has tended to that its proper subject is the psychological see the lack of immune responses under various mechanisms operating at the level of individual conditions as a failure, rather than as an adap- psychology, while theories such as the PSTS tive trade-off. focus on social variables proper. BIS mecha- The BIS concept, too, would benefit from a nisms mediate, and are shaped by, social vari- greater consideration of such trade-offs. As ables, but nevertheless constitute a distinct level noted above, the BIS is typically construed as of analysis. mediating low-cost prophylactic defenses against infection. However, the notion of “cost” Back to PNI involved here is usually restricted to the costs of CIS responses considered in themselves (e.g., If we are correct that the proper place of the metabolic costs), and is not typically situated BIS concept lies in individual-level level psy- within the nexus of selective pressures that de- chology, then we believe that employing the termine the overall evolutionary costs of psy- framework of PNI will often be preferable to chological disease avoidance. However, when utilizing the concept of the BIS. As Schaller situated within a broader evolutionary cost- notes, the BIS would better be termed the “psy- benefit perspective, psychological defenses can chological immune system” (Schaller, 2006,p. be equally or more costly than CIS responses. 97). If so, then the corresponding discipline This is abundantly illustrated in the dynamics of would best be called psycho-immunology. Such This document is copyrighted by the American Psychological Association or one of its allied publishers. disgust responses that have been the focus of a discipline already exists, and, when we incor- This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. much BIS research, as disgust responses are porate the role of the central nervous system in modulated in response to other factors, for ex- mediating psycho-immune interactions, is best ample, hunger, sexual arousal, or different labeled PNI. While research done using the BIS stages of the reproductive cycle. Such trade-offs concept certainly goes beyond existing research provide yet another reason to question the char- in PNI in its discussion of, for example, social acterization of the BIS as an exclusively pro- factors and their underlying psychology, it is phylactic response. unclear that the BIS offers an advance over Of particular importance for research into the existing concepts, or picks out some well- BIS and PSTS is the concept of the social im- defined, theoretically meaningful subset of such mune system, as articulated by Cremer and col- disciplines, via an emphasis on behavioral pro- 240 CLARK AND FESSLER

phylaxis, disgust, and so forth In any case, the level nature of PNI offers the possibility for BIS literature has thus far failed to maximize greater integration and illumination, and paying the integration of the BIS literature with well- attention to the neural, physiological, and so established disciplines and theories of the same forth levels allows us to talk about the evolution phenomena, including detailed accounts of the of different components at multiple levels, and neurophysiological mechanisms underlying in- yields insight into the evolution of the system in teractions between psychology and immune ways that approaching it solely from the (social) function developed within PNI. psychological level cannot. Such a multilevel, PNI is both more established and more inte- multidisciplinary approach is precisely what grated with other disciplines. The term was in- makes newly emerging concepts such as EI and troduced in 1975 (Ader & Cohen, 1975). There the BIS useful. are journals, textbooks, and departments of PNI, Relatedly, it might also be thought that we and a Google Scholar search for the term “psy- should see the BIS concept as concerned spe- choneuroimmunology” yields ϳ25,000 results. cifically with the evolved nature of the behav- In contrast, use of the BIS concept is new (“be- ioral, psychological, and social systems that in- havioral immune system” yields ϳ250 results), teract with and extend the immune system and has largely been restricted to a particular proper, whereas PNI is not concerned with the school of researchers. Specifically, it has by evolutionary history of the PNIS, but rather evolutionary psychologists (broadly construed) simply aims to characterize the PNIS. We think who are interested in a cluster of issues con- this would be a mistake for several reasons. cerning the influence of pathogens on psychol- First, in principle, there is nothing that should ogy and social structure, especially by social restrict the BIS to its evolved components. The psychologists interested in intergroup emotions, deployment of cultural strategies to deal with disgust in particular (Clay et al., 2012; Fincher disease would also seem to be part of the BIS, a & Thornhill, 2012; Schaller, 2011; Terrizzi et possibility hinted at in some PSTS papers (e.g., al., 2013; Thornhill et al., 2010; Tybur et al., Fincher & Thornhill, 2012). Second, there is a 2010; Van Vugt & Park, 2009). This literature is rich tradition of evolutionary theorizing within not tightly connected to the broader PNI pro- PNI, with many papers devoted to the evolution gram, in either direction: only a handful of PNI of various aspects of the PNIS (Adamo, 2006; researchers have referenced the BIS concept, Kinney & Tanaka, 2009; Maier, Watkins, & and, more surprisingly, there are very few men- Fleshner, 1994; Maier & Watkins, 1998; tions of PNI in the BIS literature, where, even if Segerstrom, 2010; Walls, 2005). If we want to one wishes to avoid an identification of BIS refer to such specifically evolutionary consider- theory with PNI, PNI is nonetheless clearly ations, then the term “evolutionary psychoneu- relevant. roimmunology” would be preferable, and more It might be thought that we should avoid consistent with the ways in which evolutionary postulating too close a relationship between the approaches to existing disciplines have been BIS and PNI on the grounds that PNI should be demarcated (e.g., evolutionary psychology). restricted to the “mechanistic” explanations of immune-psychology interactions. On this view, Conclusion the mechanisms identified by PNI might under- pin the BIS, but, strictly speaking, belong to a We hypothesize that the excitement sur- This document is copyrighted by the American Psychological Association or one of its allied publishers. different level of analysis. Some psychologists rounding, and perceived novelty of, the BIS This article is intended solely for the personal use of the individual user and is not to be disseminated broadly. see neural and physiological theories as irrele- concept may be attributable more to the grow- vant, or at least unnecessary, to psychological ing realization on the part of those in the BIS research. However, it seems to us that BIS the- literature of the importance of the kinds of pro- ory is also committed to such cross-level mech- cesses that have been identified within PNI, anisms. Furthermore, attempts to screen off the rather than to the identification of novel con- “mechanistic” level are, in our opinion both cepts or phenomena. It thereby serves as a ral- methodologically and substantively flawed, and lying point for evolutionary psychologists, and fail to take advantage of the breadth of research as an avenue for the introduction of ideas from in neuroscience, immunology, and so forth that other disciplines. It is similar in this respect to bears directly on such hypotheses. The multi- other new lines of inquiry such as EI, which RECONTEXTUALIZING THE BEHAVIORAL IMMUNE SYSTEM 241

represents less a newly demarcated field or set Chrousos, G. P. (2009). Stress and disorders of the of phenomena than the introduction of broader stress system. Nature Reviews Endocrinology, 5, findings from, for example, evolutionary devel- 374Ð381. doi:10.1038/nrendo.2009.106 opmental biology and systems biology into tra- Clark, J., & Fessler, D. (2014). The messy evolution ditional ecology and immunology, and an in- of disgust. Manuscript submitted for publication. Clay, R., Terrizzi, J. A., Jr., & Shook, N. J. (2012). creasing recognition of the intersection of Individual differences in the behavioral immune traditionally distinct disciplines. We believe system and the emergence of cultural systems. that the penetration of such awareness will be Social Psychology, 43, 174Ð184. doi:10.1027/ facilitated by grounding BIS research in PNI. 1864-9335/a000118 We believe that the overlap between PNI and Cotter, S. C., & Kilner, R. M. (2010). Personal im- the BIS concept is clear. There is a prima facie munity versus social immunity. Behavioral Ecol- case to be made that they are very often describ- ogy, 21, 663Ð668. doi:10.1093/beheco/arq070 ing the same system(s), and that BIS theorists Cremer, S., Armitage, S. A., & Schmid-Hempel, P. are effectively engaging in PNI research. In- (2007). Social immunity. Current Biology, 17, deed, work by some BIS theorists (e.g., Schaller R693ÐR702. doi:10.1016/j.cub.2007.06.008 et al.’s (2010) work on immune priming in Cremer, S., & Sixt, M. (2009). Analogies in the evolution of individual and social immunity. Phil- disgust) is exemplary of the kind of cross-level osophical Transactions of the Royal Society B: research that will be facilitated by contextualiz- Biological Sciences, 364, 129Ð142. doi:10.1098/ ing the BIS within PNI. Ceteris paribus, it is rstb.2008.0166 preferable to choose a more established term to Dantzer, R., & Kelley, K. W. (2007). Twenty years of describe a set of phenomena. Established con- research on cytokine-induced sickness behavior. cepts are preferable for the pedestrian reason Brain, Behavior, and Immunity, 21, 153Ð160. doi: that they facilitate cross-referencing, and allow 10.1016/j.bbi.2006.09.006 research over time to coalesce around particular Debnath, M., & Venkatasubramanian, G. (2013). Re- concepts. Such theoretical entrenchment is also cent advances in psychoneuroimmunology rele- usually associated with a greater degree of in- vant to schizophrenia therapeutics. Current Opin- ion in Psychiatry, 26, 433Ð439. doi:10.1097/YCO tegration with related concepts and disciplines. .0b013e328363b4da This is, after all, the goal of BIS theory. In any Denson, T. F., Spanovic, M., & Miller, N. (2009). case, whether the BIS is subsumed into PNI or Cognitive appraisals and emotions predict cortisol not, its advocates should devote more effort to and immune responses: A meta-analysis of acute articulating the relevance of the disciplines to laboratory social stressors and emotion inductions. one another. This, we think, will better capture Psychological Bulletin, 135, 823Ð853. doi: the value and novelty of BIS research, more 10.1037/a0016909 accurately reflect the intentions of BIS research- Dickerson, S. S., Kemeny, M. E., Aziz, N., Kim, ers, and better advance their aims. K. H., & Fahey, J. L. (2004). Immunological ef- fects of induced shame and guilt. Psychosomatic Medicine, 66, 124Ð131. doi:10.1097/01.PSY References .0000097338.75454.29 Duncan, L. A., & Schaller, M. (2009). Prejudicial Adamo, S. A. (2006). Comparative psychoneuroim- attitudes toward older adults may be exaggerated munology: Evidence from the insects. 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