Wednesday, December 11, 2013

Daniel Kelly, Yuck! The Nature and Moral Significance of Disgust (2011)

I have an aversion to lima beans.  aver·sion,  noun \ə-ˈvər-zhən, -shən\                                              
: a strong feeling of not liking something.  **** 2
a :  a feeling of repugnance toward something with a desire to avoid or turn from it aversion >
b :  a settled dislike :  antipathy aversion to parties>
c :  a tendency to extinguish a behavior or to avoid a thing or situation and especially a usually pleasurable one because it is or has been associated with a noxious stimulus

Yuck!  But is this aversion a form of disgust?  dis·gust noun \di-ˈskəst, dis-ˈgəst also diz-\
: a strong feeling of dislike for something that has a very unpleasant appearance, taste, smell, etc.
: annoyance and anger that you feel toward something because it is not good, fair, appropriate, etc.
:  marked aversion aroused by something highly distasteful :  repugnance
I find lima beans distasteful, noxious.  I avoid eating them.  Apparently, I am not the only one. Years ago as a child, I felt the same way toward other food items, but today only lima beans remains associated with a noxious stimulus of some kind that I cannot define.  I know well that others like lima beans and are not harmed by them, but something triggers certain neurons firing in my brain that creates this reaction to the lima bean.  Are lima beans disgusting, by which I intend to describe lima beans an elicitor of disgust?  By definition, lima beans are disgusting . . . at least to me.  dis·gust·ing, adjective
: so unpleasant to see, smell, taste, consider, etc., that you feel slightly sick
: so bad, unfair, inappropriate, etc., that you feel annoyed and angry
You see in these definitions of disgust and disgusting two distinctive feelings.  One centers on an aversion, dislike or repugnance toward something  that is distasteful, or suffers from a bad smell or appearance; although the definitions do not elaborate on what is distasteful or smells bad, it is easy to think of something associated with the mouth and ingestion such as rotten food or a poison.  The second feeling centers on a dislike for another group or behavior considered annoying or unfair by some standard.  In both cases, the consequence of the feeling is likely rejection:  rejection of the noxious substance; rejection of the other person or group.
Paul Rozin at the University of Pennsylvania and Jonathan Haidt at the University of Virginia and now NYU have devoted more attention and research to the subject of disgust than anyone else at this moment in time.  In their contribution to the 1999 edition of the Handbook of Cognition and Emotion entitled Disgust:  The Body and Soul Emotion, they made several key points and arguments:
  • Distaste and disgust are different.  Other animals, particularly other mammals, show they react to ingesting a substance because it is distasteful by rejecting it.  Disgust, on the other hand, is uniquely human because, in addition to some biological rejection of distasteful or foul smelling substance, the feeling has a cognitive content that is not elicited by sensory properties.  Like other emotions, disgust links together cognitive and bodily responses, which can be analyzed as an affect program, in which outputs (behaviors, expressions, physiological responses) are triggered by inputs (cognitive appraisals or environmental events).  While the biological outputs that represent disgust have been reasonably stable among human populations over time, there has been an enormous expansion on the cognitive appraisal side, which expansion varies with history and culture and takes disgust far beyond its animal precursors and well beyond an aversion to lima beans.
  • For humans, the elicitors of core disgust are generally of animal origin, although there is research that plants and vegetables can elicit core disgust. 
  • The rejection response is now harnessed to the offensive idea that humans are animals, and thus disgust is part of affirming our unique humanity by suppressing every characteristic that we feel to be 'animal'.  They call this animal nature disgust and distinguish it from core disgust.  The cognitive notion here includes associating something deemed disgusting with something labeled impure. 
  • There is also another form of disgust they call interpersonal disgust, which is rejection of persons outside one's social or cultural group.  Hindu caste behavior is a prime example, but there are hundreds of other examples, racial, religious, and the like, that are readily recognized.
  • Finally, thee is social-moral disgust where violations of social norms trigger a feeling of disgust.  Not all violations of social norms trigger disgust.  Bank robbery they point out, while viewed as "wrong," does not trigger necessarily disgust or rejection. 

There has been much written in recent years about disgust as a moral emotion or the potential nexus between disgust and moral judgments/ethical norms.  The example of incest avoidance is one example of "moral" behavior that is at the heart of this discussion.  Avoiding consumption of lima beans is not, and I am reasonably certain that the avoidance of lima beans is not considered a "moral behavior" across any culture or society.  Marc Hauser described disgust as "the most powerful emotion against sin, especially in the domains of food and sex. . . . In the absence of a disgust response, we might well convince ourselves that it is okay to have sex with a younger sibling or eat vomit, act with deleterious consequences for our reproductive success and survival respectively."  Incest avoidance is worthy of study -- in contrast to my aversion for lima beans -- because it is virtually universal across cultures, and is therefore almost unique among things humans generally avoid.   Aversion to eating pork, for example, is not universal, and like lima beans there is a substantial part of the human population that likes eating pork and is not harmed by eating pork.  In some cultures, the avoidance of eating pork is considered a "moral behavior." 

Disgust did not begin as a moral or even a social emotion.  There is common agreement, among those who have studied disgust that the emotion's evolutionary origins lie in response to the ingestion of something: spoiled food, toxins; it later evolved as a response to the presence of disease and parasites, which is referred to as core disgustDaniel Kelly documents this body of research in Yuck!  And a common feature of this emotion is the automatic facial feature called face gape.  As one article explains, "At its root, disgust is a revulsion response -- "a basic biological motivational system" -- that Darwin associated with the sense of taste. Its function is to reject or discharge offensive-tasting food from the mouth (and/or the stomach), and its fundamental indicator, the "gape" or tongue extension, has been observed in a number of animals, including birds and mammals. In humans, the characteristic facial expressions of disgust that coincide with gaping include nose wrinkling and raising the upper lip, behaviors usually accompanied by a feeling of nausea and a general sense of revulsion. Together these behaviors and sensations facilitate the rejection of food that has been put into the mouth."  Evolutionarily, disgust began with distaste, but at some point it adapted in humans to protect against infection by pathogens and parasites.  Daniel Kelly explains his thesis that the two responses became "entangled."  "Other previously puzzling features of disgust also fall into place once its role in parasite avoidance becomes clear.  Together, eating and sex constitute two of the most basic evolutionary imperatives.  Both behaviors are unavoidable ingredients of evolutionary success, but both involve the crossing of bodily perimeters at various points.  By virtue of this, both activities leave those engaging in them highly vulnerable to infection.  The upshot is that disgust's role in monitoring the boundaries of the entire body (rather than just the mouth) makes much more sense in light of its connection to infectious disease.  Moreover, both feeding and procreating are activities that require those boundaries to be breached.  They are highly salient to disgust both because they are universal and unavoidable and because they are two of the most potent vectors of disease transmission."  It is this entanglement of distaste and core disgust that is unique to humans.  There is evidence that each is independently found in other species.

Importantly, disgust appears to be activated in the cortex. Kelly identifies the insula, which is not part of that ancient subcortical system of the forebrain or midbrain that Jaak Panksepp documents is associated with basic emotional systems.  (See May 19, 2013 post).  The word disgust never appears in Panksepp's book and is not even found in his description of the fear system involving in the amygdala and the hypothalamus which, because fear stimulates flight, sounds like it might be related to an emotion like disgust that stimulates avoidance.  On the other hand, Kelly identifies an area of the forebrain, the putamen, as an area of the brain associated with processing disgust, but the putamen is involved in emotional facial recognition, so it may not be something disgusting that activates the putamen, but the recognition of face gape that activates the putamen.  The putamen is primarily associated with the motor cortex, so the connection to the putamen as an emotional processor is not at all that clear.  I suspect that the putamen, if it is implicated in disgust, it is not part of what Rozin and Haidt refer to as inputs (cognitive appraisals or environmental events), but our biological output that results in virtually automatic, nearly uniform facial expressions.  Research on patients with Huntington's Disease would seem to confirm this observation.  But the insular cortex is involved in maintaining the homeostatic condition of the body; it maintains an awareness of various parameters of the body;  the insula is also believed to process convergent information to produce an emotionally relevant context for sensory experience. More specifically, the anterior insula is related more to olfactory, gustatory, vicero-autonomic, and limbic function, while the posterior insula is related more to auditory-somesthetic-skeletomotor function. The insula has an important role in pain experience and the experience of a number of basic emotions, including anger, fear, disgust, happiness and sadness. If disgust is seated in the insular cortex, this would confirm the significance of cognitive appraisal in producing disgust. The insular cortex is a mammalian development, so it evolved later than those ancient emotional systems that Panksepp discusses.

Morality varies across cultures and even within cultures and smaller social groups.  Edward Westermark advanced the thesis that there was an innate aversion to sexual intercourse between persons living very closely together from early youth, and as applied to persons who are closely related this generates a feeling of horror of intercourse with close kin.  But is this aversion really innate?  Or is it learned?  Or is something innate triggered because, in this case, one must first experience living closely with someone at an early age?  Because there is survival value associated with avoiding inbreeding, there is arguably an evolutionary imperative associated with incest avoidance and should explain in substantial part why incest avoidance is universal across cultures. Inbreeding reduces the fitness of a given population. Incest avoidance seems to have nothing to do with morals.  If it is considered moral behavior, it is only because humans have put that label on a form of behavior that likely predates social norms and morals.  If it is considered disgusting, it is only because humans have put that label on it. 

Outside the example of the inversion to inbreeding, interpersonal and social-moral disgust is something that is learned.  It is not innate.  Rozin observes that up to about two years of age, children show no aversion to primary disgust elicitors such as feces.  Toilet training may be the learning event that leads to core disgust.  Later in childhood development, an event or object that was "previously morally neutral becomes morally loaded."  At this point in the learning process, disgust becomes recruited.  Disgust "becomes a major, if not the major force for negative socialization in children; a very effective way to internalize culturally prescribed rejections (perhaps starting with feces) is to make them disgusting." 

Kelly theorizes that disgust migrated from being an emotional response to toxins, parasites and disease to a socially shared emotion because face gape is automatic and the emotion as revealed in the facial gesture was communicated in a way that was empathetically received.  Like other facial communications (see July 16, 2010 post), there is a reliable causal link between the production of an emotion and its expression here that acts as a signal to avoid.  And to the extent that group selection (or more narrowly kin selection) is engaged, shared disgust becomes a survival mechanism for the group to avoid toxins, parasites and disease,  Kelly posits that the genetic underpinnings of the neural correlates of the emotion and gape face were recruited by human culture to perform several novel functions.  And what the emotion qua emotion of disgust has in common with the socially shared emotion is that the object of the emotion's attention is distasteful and/or impure.  As a cultural phenomenon, the socially shared emotion becomes connected to social, moral or ethical norms, group identity and avoidance of others.  Culture then labels something to be avoided or averted as disgusting. 

Social or ethical norms are not necessarily social or ethical norms because of a common emotional stimulus like disgust, although they could be and common aversion to foods and attitudes toward sexual behaviors within a culture are a few examples that coms to mind.  Because most social norms are learned and not instinctual, interpersonal and social-moral disgust is little more than a social label for one's attitude toward behavioral transgressions of group rules.  Interestingly, the label may not be shared by all within the group.  Consider, for examples, how societal attitudes toward homosexuality --- a behavior that large segments of many societies consider "disgusting" --- are rapidly changing.

Kelly concludes, disgust is "far from being a reliable source of special, supra-rational information about morality" and we should be extremely skeptical of claims that disgust deserves any "epistemic credit" as a trustworthy guide to justifiable moral judgments or deep ethical wisdom in repugnance.  Justifying a moral or ethical rule on disgust can easily slide in dehumanization and demonization itself, which in itself is problematic.  There is a ready and recent example that highlights Kelly's concern in today's news that the youthful leader of North Korea had his elder uncle, also in the leadership of North Korea's government, executed for treason.  In language that recalls Rozin and Haidt's discussion of animal-nature disgust, the uncle was labeled  as "despicable human scum" and "worse than a dog," and said he had betrayed his party and leader."  In other words --- particularly with the association to animals and scum (certainly there are parasites and disease in scum) --- the uncle was disgusting.  His purported "disgustingness" became a post hoc justification for his execution.

This entire discussion implicates the relationship between genes and culture, and Kelly devotes an entire chapter to "gene culture coevolution," sometimes referred to as the dual inheritance theory.  (See September 12, 2012 and June 17, 2010 posts) and its application to the evolution of disgust. Rozin and Haidt concur:  "The interaction between biology and culture is clear, because the output side of disgust remains largely ruled by biological forces that originally shaped it, while the input/appraisal/meaning part has been greatly elaborated, and perhaps transformed in some cases."

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