Morality, Disgust and the Territorial Imperative

Morality, Disgust and the Territorial Imperative

Print Friendly, PDF & Email

Increasingly psychologists and biologists have been supporting the view that emotions may be the phylogenetic building blocks of moral intuitions by providing neural substrates for emotional behavior (e.g. Damasio, 1999, 2003; deWaal, 1996, 2006;  Haidt, 2001, 2004; Hauser, 2006).  Both Haidt and deWaal have proposed a number of emotional elements contributing to moral intuition which may be found at least in great apes and perhaps additionally in some other mammals. The first of these evolutionarily prepared domains is altruism, including kinship ties, food sharing and group selection. The second is based on rank and authority relationships and includes deference, respect, and shame (Haidt, 2004). The third  involves reciprocity, concern for justice, fairness and revenge.  Haidt and Joseph (in press) have recently expanded their list of emotional underpinnings of morality to five to include a sense of ingroup loyalty, and lastly a concern for moral purity and avoidance of contamination.

The extent of the influence on human moral processing played by these innate building blocks is a subject of ongoing debate. While  Hauser (2006) in keeping with evolutionary psychology,  opts for rather dedicated moral modules similar to Chomsky’s language modules, Prinz (2007) takes the opposite antinativist view that the prepared domains described above evolved to serve other functions and therefore morality is akin to a spandrel. A more nuanced version of the nativist view suggests that:   “The first draft of the moral mind has diverse moral content that was specified in advance of experience, but this innately given content gets revised and greatly extended during the course of development … within a cultural context…” (Haidt & Joseph, in press). Eschewing both extremes, we prefer the middle of the road approach on the basis that evolution is a great tinkerer and often uses old structures to perform new functions. Our view is not based on strict Fodorian modules but on the assumption that evolutionary history constrains and biases human morality, without at the same time providing a sufficient basis for moral development.

If indeed emotions provide prepared neural circuits available to interact with development and culture to influence our moral cognitions,  it should be of paramount importance  to define which emotional systems in fact are inbuilt  primary systems based on phylogenetically selected mechanisms. Although many lists of primary emotions have been suggested, Panksepp (1998) has provided a list of  emotional operating systems based on by neural criteria  which include genetically predetermined circuitry, and the ability to organize diverse behaviours.  Panksepp’s convention, which we will follow here, is the use of capitals to distinguish these operating systems from subjective feelings. These systems designated SEEKING, RAGE, FEAR, LUST, PANIC, CARE, and PLAY organize complex but flexible reactions to stimuli by activating or inhibiting autonomic, hormonal and somatic changes that were adaptive during evolutionary history. The specific combination of behavioral components will depend on context and eliciting stimulus. In previous papers (Toronchuk & Ellis, 2007a, b)  we have suggested the addition of a DISGUST and a POWER system to this list of basic emotional systems and we attempt to show below how these two systems contribute to the evolution of moral intuitions.

From the dawn of vertebrate evolution the basic social problems facing individuals have involved finding mates and competing with others for those mates, but for many vertebrates social interactions remain sparse. The development in mammals of lactation presented the challenge of caring for offspring and furthered the development of an emotional system of attachment to offspring, which in some mammals broadens to include others in the social group. Consistent with the suggestions of Haidt and deWaal, the CARE or nurturance system described by Panksepp (1998) plays an obvious role in moral intuitions and may provide the underlying basis for various forms of altruism arising phylogenetically from the need for all mammals to care for their offspring. Reciprocity and fairness in primates, we suggest, may derive in part from Panksepp’s PLAY system which appears evolutionarily in mammals functioning so that young individuals may learn appropriate social behaviors. The RAGE system is also likely involved in reciprocity underlying the desire to punish cheaters.  We propose that these emotional operating systems are accessible in humans and influence the content of moral behaviours, as described by Haidt and Joseph. In addition different neural circuitry and unique selection pressures, allows each one a relatively independent influence on moral intuition. We expect the neural circuitry  for these emotions to be partially overlapping because of the tendency for evolution to co-opt existing mechanisms for new functions; nevertheless we expect to be able to discern separate evolutionary tendencies albeit without encapsulated modules.

POWER and the territorial imperative
In addition to the emotional systems listed by Panksepp,  we have proposed a genetically determined emotional system concerned with territoriality, dominance and subordination. Panksepp (1998) has equivocated on this system and suggested that social dominance arises instead from interactions between the childhood PLAY system and the FEAR and RAGE systems. While this may occur during ontogenetic development of individual mammals, we propose that this system is evolutionarily more ancient than play because dominance displays, usually related to territory and/or access to females, are found in many species of lizards, and even fish. This ancient system allowed competition for mates, territories and other material resources and later gave rise to competition for status and social approval. Originally instinctual behaviours were patterned by the striatal complex of MacLean’s “reptilian brain” (1990), with the addition of further limbic emotional components in mammals. The development of neocortex in humans allowed for complex integration of these emotional components with cognition leading to the emergence of secondary moral emotions such as guilt, and shame. We expect that the primary emotional POWER system would influence  the authority/subordination domain described by Haidt and to a lesser extent the domain involving reciprocity, revenge, fairness and concern for justice. 

DISGUST and disease are “in bad taste”
We have argued elsewhere that disgust is a basic emotional operating program evolved in lower vertebrates as a protective mechanism to prevent contact with or ingestion of disease-producing material. (Toronchuk & Ellis, 2007a, b).  The DISGUST system arose phylogenetically in response to danger to the internal milieu from pathogens and their toxic products. Our proposal was prompted by the recognition that the innate immune system predates the nervous system and all multicellular organisms have mechanisms for rejection and/or elimination of microbes and parasites. These mechanisms which originally provided defense by regulating consummatory behaviours gave rise to a primary emotional system which facilitates evaluation of reinforcers and functions to motivate avoidance Disgust, according to Rozin, Haidt and colleagues (Rozin & Fallon 1987; Haidt, Rozin, McCauley, & Imada, 1997) is more than avoiding bad taste; it hinges on avoidance of contamination. Distasteful things are not always disgusting nor are disgusting things necessarily distasteful.

While Rozin and Haidt see only human disgust as contamination related, we differ in suggesting that the theme of disease avoidance has a long evolutionary history (Toronchuk & Ellis 2007a). The disease-avoidance origin of disgust is supported by the results of a massive international survey (Curtis, Aunger, & Rabie, 2004) showing that disgust is universally elicited by disease-salient contact stimuli such as bodily secretions, viscous substances, vermin and sick or dirty people. Further examples of social avoidance in animals of pathogen infested individuals and potentially infested substances are provided by Curtis (2007).  Miller (1997 p.19) shows convincingly that touch, especially “the slimy, slithery, viscous, oozing, festering, scabby, sticky, and moist” can be as effective as bad taste in eliciting disgust. A recent study has shown that people are more likely to wash their hands after  for an implicit threat to moral purity, confirming an association between moral and physical cleansing (Zhong & Liljenquist, 2006).

Our proposal is that nutritional-, sexual-, and socially-related stimuli plus ideational components are all able to activate either the SEEKING or DISGUST systems in analogous ways. The evolutionary trajectory from illness-related reactions, proceeded through more complex learned aversions and avoidance responses, to human core disgust which eventually gave rise to a secondary emotion encompassing socio-moral attributes. It is well known that animals avoid foods which have been paired in the past with illness giving rise to conditioned taste aversions (reviewed in Toronchuk & Ellis, 2007a). In the same manner it has been shown that rats will avoid copulation after illness (Peters, 1983) on the one hand reminiscent of social disgust in humans and on the retaining the illness-avoidance base seen in conditioned taste aversions.

In his proposal of an “emotional immune system”, Schaller shows how evolutionary bias to avoid others who are different may give rise to xenophobia (Schaller & Duncan, 2007). We not only avoid others with obvious disease-related contamination but avoid sexual contact with others who have differences from the norm—including asymmetries, disabilities and obesity—because difference from the norm may signal underlying ill health or poor genetic potential. Foreigners are also more likely to carry pathogens for which we have no immunity. Schaller’s theory thus bridges the disease- avoidance function of disgust with emotional prohibitions concerning touch and sexual contact with others.  Morals become biologically biased to reflect rules for sexual contact and social proximity, and enable individuals to discount those from out-groups as contaminated. Thus we propose the DISGUST system not only influences the domain of moral purity but also Haidt’s domain of ingroup loyalty.

Ancient cortex, modern cells
The primary taste cortex  is found in the anterior insula (AI), an ancient structure at the border between non-cortical areas and the more fully developed neocortex. The insula also plays an important role in interoceptive functions and a necessary role in both the experience of human disgust and taste-aversion learning in animals (reviewed in Toronchuk & Ellis,  2007a). In primates the sensory input pathway to the AI comes directly from the thalamus rather than indirectly via the amygdala as in other animals. This primate innovation allows the insula in primate to inform the lower structures instead of lower centers (amygdala and striatopallidum) remaining the major focus for valuation of stimuli.  Thus the primate pathway, in contrast to others, allows greater cortical integration of sensory inputs from multiple modalities. The human insula, as described by Craig (2003, 2005) has come to play a major role instantiating the distinctively human experience of consciousness and self awareness. The AI and adjacent orbito-frontal areas are activated during subjective pain, embarrassment, guilt and moral decision making as will be discussed below. Heimer and Van Hoesen (2006) even suggest that the right anterior insula is not only crucial for emotional awareness, but “the final breeding ground for subjective feeling states”.

Anterior insula is adjacent and continuous with the prefrontal cortex, an area in which damage has been shown by Damasio and his colleagues (Damasio, 1996; 1999)  to be involved in deficits in moral behavior.  These moral deficits exist in spite of normal intellectual processing but co-exist with impaired autonomic responses to emotionally- charged pictures leading Damasio to conclude that emotions are necessary for normal judgments of right and wrong.   A recent clinical study (Koenigs, Young, Adolphs, Tranel, Cushman, Hauser & Damasio, 2007) shows that individuals with damage to this area produce abnormal responses to moral dilemmas, even though they show normal cognitive processing of moral dilemmas. These patients were able to make utilitarian judgments, but not emotionally based moral judgments. Autistic individuals also show dysfunction in this area (Dapretto, Davies, Pfifer, Scott, Sigman, Bookheimer et al., 2006).

The fronto-insular and anterior cingulate cortices (a similar transition type of cortex) contain a recently evolved cellular type, the von Economo neuron (VEN). These cells are unique to humans and African great apes but far more abundant in the former and concentrated on the right side. (Nimchinsky, Gilissen, Allman, Perl, Erwin & Hof, 1999)  VENs have been variously hypothesized as involved in expectancy of reward and punishment, human social intuition and formation of a theory of mind. Self-awareness only arises in humans, great apes, and perhaps dolphins i.e. those animals with von Economo neurons (VENs) in the insula. Consistent with a proposed role for VENs in self awareness, humans attain their full compliment of VENs only at about 4 yrs of age.

Although the role of VENs in disgust is not known, it is interesting that VENs are unique in the central nervous system in having serotonin type 2b receptors, a receptor subtype otherwise abundant in the stomach and intestines. Serotonin plays a major neural role in nausea and vomiting. Disgust is also linked via serotonergic mechanisms to gut motility, as befits the original function of disgust in avoiding ingestion and vomiting of noxious substance.  VENs also contain receptor sites for the neuropeptide vasopressin (Allman, Watson, Tetreault, & Hakeem, 2005) well known for its neural role in social bonding but less well known to be involved with production of nausea.

 Frontotemporal dementia, in which emotional and social awareness, and empathy, theory of mind are disrupted,  specifically targets VENs  in the fronto-insular and anterior cingulate areas (Seeley, Carlin, Allman,  Macedo, Bush, Miller, et al., 2006). There is evidence from both EEG and fMRI studies that autistic disorders, which involves deficits in the theory of mind in others also involves dysfunctioning in these cells (Dapretto, 2006; Oberman, Hubbard, McCleery, Altschulera, Ramachandrana, & Pinedad, 2005). All of this evidence is consistent with Damasio’s finding that patients with frontal damage lack the ability to process emotional dilemmas.  

Thus the appearance of von Economo neurons in the insula and adjacent orbitofrontal area is perhaps associated with the development of theory of mind and moral reasoning. This development might be considered a preadaptation influenced by the role of the insula in awareness of the bodily state of self and others—a role originally arising from the need to evaluate and avoid contact with and contamination by noxious substances. While we are far from postulating a moral module, it is clear that the fronto-insular area, originally involved in evaluating “good taste” and “bad taste” has developed evolutionarily to be a necessary component of the neural circuitry for empathy, judging fairness, and the making moral decisions.

“As if” loops
Core representations of the body arising from structures such as the insula may play a role not only in self-awareness, but also in an “as-if” loop system that allows evaluation and anticipation of events (see e.g. Bechara & Damasio, 2005; Damasio, 1999). Goldman and Sripada (2005) have pointed out that the reading of basic emotions in the faces of others may have unique survival value involving specialized neural programs which attribute a state in another based on simulation of that state in oneself. They note this may be accomplished by a reverse simulation which, if not dependent on actual feedback, would require an “as-if“ loop. The somatic marker hypothesis of Damasio (1996) proposes the role of the insula is primarily to provide sensory representation of the bodily state as part of this as-if loop mechanism.

This same “as if” loop mechanism might function in perceiving the bodily states of others. For example it has been shown, using the same subjects, that activity in AI subserves both the experience of disgust and its recognition in others (Wicker, Keysers, Plailly, Royet, Gallese, & Rizzolatti, 2003). In the same manner both physical pain as well as anticipation of pain in a loved one activate AI, and individual empathy scores correlated with the amount of activity while the other experienced pain (Singer, Seymour, O’Doherty, Kaube, Dolan, & Frith, 2004). Furthermore AI activity in response to pain in another person was modulated by the perceived fairness of that person (Singer, Seymour, O’Doherty, Stephan, Dolan, & Frith, 2006). Unfair offers of monetary reward, suggested by the authors as a form of emotion-based disgust, also activate (Sanfey, Rilling, Aronson, Nystrom, & Cohen, 2003). AI is also somewhat activated by unpleasant moral scenarios perhaps also related to activation by disgusting stimuli (Moll,  Oliveira-Souza,  Eslinger, Bramati,  Mour„o-Miranda,  Andreiuolo, et al., 2002). Another recent study showed that neurons in the gustatory cortex of AI and neighboring frontal cortex become activated when participants view either pleased or disgusted facial expressions of others (Jabbi, Swart & Keysers, 2007). In this study the amount of activation correlated with self-reported measures of empathy, specifically measures of emotional arousability and ability to transpose the self into feelings and behaviors of others, but not with sympathy.

We don’t yet know for sure what the role of VENs in “as if” loops might be, but it would be consistent if they were involved in the neural simulations which make empathy possible. Thagard (2006) has argued that our understanding of other people via neural mirroring provides a more direct understanding of others than our verbal versions of why people behave the way they do and links these neural simulations with Nichols’ idea (Nichols, 2004) that norms resonate with out emotions and hence some are easier to learn than others.

The shortcomings of emotional intuition
This paper hypothesizes that human moral intuition has a long phylogenetic history, originating in part from a secondary emotional system arising out of the rejection response of organisms to potentially dangerous substances, continuing through vertebrate distaste responses, conditioned responses to illness, and the human emotional response of disgust to repulsive objects and behaviors. Additional influences were provided by the ancient emotional system governing social ranking and the territorial imperative, which also associated in humans with feelings of right and wrong. While emotions contribute to moral feelings, many emotional operating systems such as LUST, SEEKING and ANGER also prompt individual “selfish” behaviors.  As frequently noted, almost all the social behavior of animals directly benefits the reproductive success of the individual either directly or indirectly. Rarely or never are behaviours which benefit others while directly harming the individual intentionally carried out.

Darwin pointed out in Descent  that the appetites and social instincts have different effects on behavior. While the appetites are sharp and episodic, the social instincts are calming and constant acting. (cited in Korsgaard, 2006).  Darwin’s distinction is useful in comparing the effects of the emotional operating systems. The appetitive systems of SEEKING and LUST along with RAGE  are more likely to tend toward selfish behavior while the more social CARE system and at times PLAY facilitate empathic or altruistic behaviors. DISGUST activates the parasympathetic system, consistent with Darwin’s claim for a calming influence in opposition to the excitatory appetites. However it seems to us that both DISGUST and POWER may be used in the service of both selfish and morally prosocial behavior. The DISGUST circuitry  both activates avoidance of “bad”, “contaminating” or “dirty”  behaviours and may lay a neural basis for self-awareness, empathy and  transcendence of the self. On the other hand DISGUST also fosters us to avoid anyone who looks, smells or acts different leading to outgroup hatred, xenophobia,  and apartheid. The POWER emotional system may likewise influence reciprocity and fairness, but is all too often used to subordinate others. Chimps may show rudiments of morality within their own group, but purposeful, seemingly premeditated territorial “wars” with nearby groups can result in death and even annihilation of whole groups. 

Although moral intuitions are influenced by emotions, moral reasoning is cognitively based, and hence is more deeply influenced by culture. This includes the influence of moral leaders in the community who themselves may or may not be in accord with the locally accepted moral practices providing another measure of ambiguity. Although evolutionary mechanisms provide  certain biases in moral development, evolution by itself, however, cannot underlie the development of genuine morality, entailing the power to bring about moral universals or a universal altruism (love for the enemy). It seems unclear how we might move from kinship and group altruism to universal morality and deeper (kenotic) love of enemies without some form of example, inspiration or revelation.

The phylogenetically older mostly individualistic emotions easily conflict with the newer mammalian prosocial emotions leaving organisms in internal conflict. The advancement of  human cognitive abilities adds newer layers of potential internal conflict, because various cognitions also conflict with each other. In addition  studies on moral dilemmas (e.g. trolley and bridge dilemmas) indicate that moral intuition and moral reasoning also conflict with each other at times. In humans a third additional source of conflict arises due to  self awareness which allows us to recognize our predicament as we attempt to view ourselves objectively. Neither emotion nor rationality therefore provide assured mechanisms for moral behavior or self-transcendence (Ellis, 2007). The human condition seems to entail inevitable internal conflict as many religious traditions suggest. It is at this point that faith and hope are necessary in order to find a larger telos and meaning in life (fig.1).

Figure 1


Figure 1: Each of Rationality, Emotions, Ethics, Faith and Hope help to determine our choices.  They are modulated by the society in which we live and cannot be understood in isolation. (modified from Ellis, 2007).Figure

Major world  religions boot strap on kin altruism by reminding adherents of the universal brotherhood of man and fatherhood of  God in order to encourage universal morality. They also encourage activation of a different sort of “as if” loop (treat others as if you were the recipient of your own behavior).  Religious practices when personally appropriated also provide many types of top down processes which may then come to guide moral decision making. By actively choosing to channel thought processes, higher order processes are able to limit, direct and channel the lower order processes which make up the building blocks of self (see Murphy & Brown, 2007).  The guiding values on which we make our choices, however, must come from outside science, through faith and hope (Ellis, 2007; fig 2). We propose that personal faith and hope are the essential components without which emotion and rationality come short of  kenotic love.

Figure 2


Figure 2: The nature/nurture issue: the three main factors that contribute to the development of the mind (social environment, natural environment, biological inheritance) are all partial causes in our decisions. The innate emotional operating systems become the basis for human emotion, which influences rationality, which in turn influences values and ethics, but all of these are influenced by the wider environment. Our own personal choice is the final determinant. (modified from Ellis, 2007).


Allman, J.M., Watson, K.K., Tetreault, N.A., & Hakeem, A.Y. (2005).Intuition and autism: a possible role for Von Economo neurons. Trends in Cognitive Science, 9,     367–373.

Bechara, A., & Damasio, A.(2005). The somatic marker hypothesis: A neural theory of economic decision. Games and Economic Behavior 52, 336–372.

Craig, A. D. (2002). How do you feel? Interoception: the sense of the physiological condition of the body. Nature Reviews: Neuroscience, 3(8), 655-666.

Craig, A.D. (2003). Interoception: the sense of the physiological condition of the body. Current Opinion in Neurobiology, 13, 500–505.

Curtis, V. (2007). A natural history of hygiene. Canadian Journal of Infectious Disease and Medical Microbiology 18, 11-14.

Curtis, V., Aunger, R., & Rabie, T. (2004). Evidence that disgust evolved to protect from risk of disease. Proceedings of the Royal  Society of London. Series B. Biological    Sciences, 271, 131-133.

Damasio, A.R. (2003). Looking for Spinoza. New York, NY: Harcourt.

Damasio, A.R. (1999). The feeling of what happens: body and emotion in the making of consciousness. New York, NY: Harcourt.

Damasio. A.R. (1996). The somatic marker hypothesis and the possible functions of the prefrontal cortex. Philosophical Transactions of the Royal Society London., B Biological Sciences, 351, 1413-1420.

Dapretto, M. , Davies, M.S., Pfeifer, J.H., Scott, A. A., Sigman, M., Bookheimer, S.Y. & Iacoboni, M. (2006). Understanding emotions in others: Mirror neuron dysfunction in children with autism spectrum disorders. Nature Neuroscience, 9, 28-30.

de Waal, F. (2006). The tower of morality. In F. deWaal, S. Macedo & J. Ober (eds.). Primates & Philosophers: How Morality Evolved.  Princeton University Press.

de Waal, F. (1996). Good natured: The origins of right and wrong in humans and other animals. Cambridge, MA: Harvard University Press

Ellis, G.F.R. (2007). The myth of a purely rational life. Theology & Science 5, 87-100.

Goldman, A. I. & Sripada, C. S.(2005). Simulationist models of face-based emotion recognition. Cognition, 94, 193-213.

Haidt, J. (2001). The emotional dog and its rational tail: A social intuitionist approach to moral judgment. Psychological Review, 108, 814-834.

Haidt, J. (2004).The emotional dog gets mistaken for a possum. Review of General Psychology, 8, 283-290.

Haidt, J.  & Joseph, C. (in press) The moral mind: How five sets of innate intuitions guide the development of many culture-specific virtues, and perhaps even          modules. In P. Carruthers, S. Laurence, and S. Stich (Eds.) The Innate Mind, Vol. 3 Foundations and the Future. Oxford.

Haidt, J., Rozin, P., McCauley, C. R., & Imada, S. (1997). Body, psyche, and culture: The relationship between disgust and morality. Psychology and Developing Societies, 9, 107-131.

Hauser, M.D. (2006) Moral Minds: How Nature designed our universal sense of right and wrong. New York: Harper Collins

Heimer, L.,& Van Hoesen, G. W. (2006). The limbic lobe and its output channels: Implications for emotional functions and adaptive behavior. Neuroscience and Biobehavioral Reviews 30, 126-147.

Jabbi , M., Swart, M., Keysers, C. (2007). Empathy for positive and negative emotions in the gustatory cortex. Neuro Image, 34, 1744-1753 .

Koenigs, M., Young, L., Adolphs, R., Tranel, D., Cushmark, F., Hauser, M. & Damasio, A. (2007). Damage to the prefrontal cortex increases utilitarian moral judgements. Nature, in press.

Korsgaard, C.M. (2006).  Morality and the distinctiveness of human action In F. deWaal, S. Macedo & J. Ober (eds). Primates & Philosophers: How Morality Evolved. Princeton University Press.

MacLean, P. (1990). The triune brain in evolution: Role in paleocerebral functions. New York, NY: Plenum.

Miller, W.I. (1997). The anatomy of disgust. Cambridge, MA: Harvard University Press.

Moll, J., Oliveira-Souza, R., Eslinger, P. J., Bramati, I. E., Mour„o-Miranda, J., Andreiuolo, P.A., et al.(2002). The neural correlates of moral sensitivity: a functional magnetic resonance imaging investigation of basic and moral emotions. The Journal of Neuroscience, 22, 2730-2736.

Murphy, N. & Brown, W.S. (2007) Did my neurons make me do it?: philosophical and neurobiological perspectives on moral responsibility and free will. Clarendon Press.

Nichols, S. (2004). Sentimental rules : on the natural foundations of moral judgment. Oxford: Oxford University Press.

Nimchinsky, E. A., Gilissen, E., Allman, J. M., Perl, D. P., Erwin, J. M., & Hof, P. R.(1999). A neuronal morphologic type unique to humans and great apes.   Proceeding of the National Academy of Sciences, USA, 96, 5268-5273.

Oberman, L.M., Hubbard, E.M., McCleery, J.P., Altschulera, E.L.,  Ramachandrana, V.S., Pinedad, J.A. (2005). EEG evidence for mirror neuron dysfunction in autism spectrum disorders. Cognitive Brain Research, 24, 190–198.

Peters, R.H. (1983). Learned aversions to copulatory behaviors in male rats. Behavioral Neuroscience. 97, 140-145.

Rozin, P., & Fallon, A. (1987). A perspective on disgust. Psychological Review, 94, 23-41.

Panksepp, J. (1998). Affective neuroscience, The foundations of human and animal emotions. London: Oxford University Press.

Prinz, J. (forthcoming). Is morality innate? In W. Sinnott-Armstrong (ed.). Moral Psychology. London: Oxford University Press.

Sanfey, A. G., Rilling, J. K., Aronson, J. A., Nystrom, L. E., & Cohen, J. D. (2003). The neural basis of economic decision-making in the ultimatum game. Science, 300, 1755-1758.

Schaller, M., & Duncan, L. A. (2007). The Behavioral Immune System: Its Evolution and Social Psychological Implications. In J. P. Forgas, M. G. Haselton, & W. von Hippel (Eds.), Evolution and the social mind: Evolutionary psychology and social   cognition. New York: Psychology Press.

Seeley, W.W., Carlin, D.A,. Allman, J.M.,  Macedo, M.N.,  Bush, C.,. Miller, B.L.&   DeArmond, S.J. (2006). Early frontotemporal dementia targets neurons unique to apes and humans. Annals of Neurology, 60, 660–667.

Singer, T., Seymour, B., O’Doherty, J., Kaube, H., Dolan, R. J., & Frith, C. D. (2004). Empathy for pain involves the affective but not sensory components of pain. Science, 303, 1157-1162.

Singer, T., Seymour, B., O’Doherty, J. P., Stephan, K. E., Dolan, R. J., & Frith, C. D. (2006). Empathic neural responses are modulated by the perceived fairness of others. Nature, 439, 466-469.

Thagard, P.( 2006). I feel your pain: mirror neurons, empathy and moral motivation. Retrieved from internet

Toronchuk, J.A. & Ellis, G.F.R (2007a). Disgust: Sensory Affect or Primary Emotional  System? Cognition and Emotion in press.

Toronchuk, J.A. & Ellis, G.F.R (2007a). Criteria for basic emotions: Seeking DISGUST? Cognition and Emotion in press.

Toronchuk, J. A. & Ellis, G.F.R.(forthcoming). Affective neuronal Darwinism: the nature of the primary emotional systems.

Wicker, B., Keysers, C., Plailly, J., Royet, J. P., Gallese, V., & Rizzolatti, G. (2003). Both of us disgusted in my insula: The common neural basis of seeing and feeling disgust. Neuron, 40, 655-664.

Zhong, C.-B., & Liljenquist, K. (2006). Washing away your sins: threatened morality and physical cleansing. Science, 313, 1451-1452.