BRIEF COMMUNICATION

Review of Daniel Kelly: Yuck! The Nature and MoralSignificance of Disgust

Cambridge MA: MIT Press, 2011, 194 pp. $30.00/£20.95.

Marta Gil

Received: 25 October 2012 /Accepted: 4 November 2012 /Published online: 16 November 2012# Springer Science+Business Media Dordrecht 2012

Abstract Perhaps the most remarkable feature aboutthis book is the effort made by its author in order toshed light on the most intriguing question that sur-rounds disgust: how is it possible for disgust to be soflexible with its objects? This book is highly recom-mended for those readers interested in the latest andmost exciting aspects of current scholarship on thestudy of the emotions. Readers too who are interestedon evolutionary psychology, moral psychology orneuroethics will find this book stimulating. However,it should be noted that perhaps it may not be liked forreaders allergic to evolutionary approaches and thevocabulary of cognitive science.

Keywords Emotions . Disgust . Moralpsychology . Evolutionary psychology

The study of the emotions has been an issue that hasamazed thinkers since the beginning of the history ofphilosophy. But what seems noteworthy is that disgustis considered a moral emotion in current discussions.Emotions like compassion, admiration, shame or guilt

have received much more attention in the literaturethan has disgust.

Interest regarding this repulsive affect whose sim-ple mention makes us feel uncomfortable has in-creased in a striking way in the last years. Theperson who has contributed most to attract attentionto this emotion has been the psychologist Paul Rozin,who started to investigate disgust in the 1980s con-ducting some unusual and outstanding empirical stud-ies. Nowadays disgust has become a hot topic ofdiscussion amongst scholars, according to JonathanHaidt [1].

The most salient feature of this emotion is its dualnature: on the one hand, we refer to disgust as a merephysiological reaction, as a universal phenomenonthat gives rise to shared behavioral patterns in allhuman beings; on the other hand, we know that it isa cultural product since what makes us feel disgust ishighly dependent on our socialization and early learn-ing. Thus, there is a wide range of objects that cantrigger the emotion: feces, wounds, cockroaches, etc.But, on another level, we feel disgusted by things likeincest, racism… or even because of an unfair offer inthe ultimatum game [2]. And even if it seems inexpli-cable at first sight there are certain people or socialgroups that carry a social stigma and have been con-sidered disgusting in some historical moments (e. g.:homosexual, women, lower castes, etc.). In such casesdisgust is not a mere reaction determined by ourphisyology, but an emotion that acquires a moral andpolitical content. According to Kelly, the intention

Neuroethics (2013) 6:221–223DOI 10.1007/s12152-012-9171-7

M. Gil (*)Department of Moral and Political Philosophy andPhilosophy of Law, University of Valencia,Av. Blasco Ibáñez, num. 30,46010 Valencia, Spaine-mail: Marta.Gil@uv.es

behind his study is to make a contribution to the“project of understanding the nature of morality ingeneral, from its evolution, psychology, and culturaltransmission, to its justification and ontology (p. 9)”.

The first chapter is conceived as a systematic studyof the empirical literature on the topic, as well as anorganization work. As Kelly points out, the analysis ofdisgust has always been diverse and has been con-ceived from very different points of view. A merecompilation of information would have been “theequivalent of a bad cubist painting that tries to repre-sent its object from every angle at once” (p. 3). Thechapter is also devoted to deepen the reader’s under-standing of what Kelly calls the disgust behavioralprofile. That means to examine the patterns of behav-ior that go along with this emotion. Kelly alsodescribes the different objects that usually trigger thisemotional reaction. The author closes this chapterintroducing a functional model of the system of dis-gust in human beings, making a description of thecognitive architecture that different mechanisms relat-ed to the emotion have.

The second chapter focuses on the study of the roleof disgust from an evolutionary point of view. In orderto explain the origins and development of this emo-tion, Kelly postulates the Entanglement thesis. Withthis hypothesis the author holds that disgust has notonly one function, but two different functions. In thesame way, he maintains that the components of theexecutive system of disgust have two different evolu-tionary etiologies. This means that from an evolution-ary perspective there are two specific mechanisms,each one with a different origin and role, which ledhuman beings to have this emotion. While the firstmechanism would be related to diet and protectionagainst potential toxic food, the second one would beassociated with pathogens, parasites and contagionprevention. Thus, the author postulates two separatesystems that developed through human evolution: afood avoidance system (it protects us from oral incor-poration of dangerous substances), and a pathogen orcontaminant avoidance system (this one is more gen-eral). In appearance, it’s difficult to figure out why thistwo distinct categories of dangers (food, on the onehand, and contamination, on the other) can cause thesame physiological and emotional reaction. This is thereason why Kelly proposes a hypothesis that connectsand entangles both systems in a certain moment of ourevolutionary history.

Kelly emphasizes a curious and remarkable fact:disgust is an emotion that we do not share with anyother creature of the animal kingdom. The author endsthe chapter trying to find an explanation for the uni-versality of disgust. Disgust is an emotional reactionthat exists in every culture. Kelly also addresses thequestion of why disgust can be provoked by such awide range of phenomena.

The third chapter deals with the different ways inwhich human beings express and recognise this emo-tion. This is what Kelly calls disgust’s sentimentalsignaling system. The author supports the idea thatthe expression and recognition of the disgust face inhumans is an automatic and unconscious process.While keeping an eye on this fact, the author high-lights another striking phenomenon: when we recog-nise disgust in another’s face, empathetic mechanismsbecome operative. Therefore, the recognition of dis-gust in the facial expression of others involves theactivation of the same cerebral circuit in ourselves,giving rise to a sort of mitigated episode of theemotion.

Kelly suggests two models in order to explain theoperating mode of the disgust sentimental signalingsystem. In the first place, he introduces the ClassicCommitment model. This model explains disgust andits recognition in terms of cooperation and deceptiondynamics. The Cultural Transmission model, on theother hand, explains these phenomena making refer-ence to social learning, pedagogy and the role ofemotions as a vehicle of cultural transmission. Afterreviewing both models, Kelly opts for the second one.Relating the Cultural Transmission model with theEntanglement thesis, Kelly explains that the disgust’ssentimental signaling system allows human beings tolearn about what is dangerous, inedible or contaminat-ing. The author acknowledges this way that disgust isan automatic response set by evolution, but he callsattention to its flexibility when it is shaped by culture.Thus, this explanation accounts for the cultural varia-tion concerning the objects that can cause thisemotion.

I found the fourth chapter one of the most interest-ing parts of the volume. It addresses the challengingquestion of the role of disgust in moral psychology.Taking as the starting point disgust as a reaction thatappears when we are faced with objective threats tosurvival, the author also reflects on the cultural aspectsof this emotion. Thus, evolution does not lead us

222 M. Gil

exclusively towards the avoidance of potential sourcesof contagion, but to be sensitive to the differencesbetween tribal groups, and to the markers that distin-guish the members belonging to the same group fromthe members of an outgroup (e.g.: skin colour, appear-ance, strange behaviors, etc).

There are two main ideas in this chapter: on the onehand, Kelly assumes that the genetic and culturalevolution has led human beings to acquire a uniqueset of tribal instincts; on the other hand, the authorpostulates the Co-opt thesis, that states that evolutionhas made the most of the physiological mechanism ofdisgust, connecting it with social norms and values.

Kelly explains the moral relevance of disgust, em-phasizing human beings’ ability to coordinate socialinteractions and social behaviors using norms with theaim of adapting better to the environment and survive.The author maintains that ethnic boundary markershave an evident emotional nature. Racism, xenopho-bia and the vision of others as inferior, contaminant oreven subhuman beings has its evolutive explanation inthis psychological mechanism that leads us to showfavoritism for the members of our own group and toreject the members of other groups.

In the fifth and last chapter the descriptive perspec-tive is abandoned, and Kelly adopts a normative ap-proach to consider some challenging questions: whensomething is regarded as disgusting by the majority ofindividuals, it is legitimate to consider it as immoral?Should disgust play a role in moral deliberation? Can asocial practice, a lifestyle or a private activity be morallyproblematic if it causes disgust? Are these reactionsappropriate to guide moral institutions? Are those kindof judgements analogous to the judgements about whatis correct or incorrect from the moral point of view?

Perhaps the most remarkable feature about thisbook is the effort made by its author in order to shedlight on the most intriguing question that surrounds

disgust: how is it possible for disgust to be so flexiblewith regard to its objects? This book is highly recom-mended for those readers interested in the latest andmost exciting aspects of current scholarship on thestudy of the emotions. Readers too who are interestedon evolutionary psychology, moral psychology orneuroethics will find this book stimulating. However,it should be noted that perhaps it may not be liked byreaders allergic to evolutionary approaches and thevocabulary of cognitive science. In case the readerwishes to find complementary perspectives I wouldrecommend the reading of William Ian Miller’s work[3] or Martha Nussbaum’s work [4]. This last author,for example, adopts a more philosophical point ofview, focusing on the critique of the role of this emo-tion in law and social life.

Acknowledgments The work of the author is supported bythe Research Project FFI2010-21639-C02-01 “DiscursiveEthics, Democratic Politics and Neuroethics” funded by theMinistry of Science and Innovation (Spanish Government) andERDF (European Union).

Conflict of Interest Statement The author declares that thereis no conflict of interest.

References

1. Chapman, Hanah A., D.A. Kim, J.M. Susskind, and A.K.Anderson. 2009. In bad taste: Evidence for the oral origins ofmoral disgust. Science 323: 1222–1226.

2. Bennett, Drake. 2010. The surprising moral force of disgust.http://www.dallasnews.com/opinion/Sunday-commentary/20100827-Drake-Bennett-The-surprising-moral-3508.ece.Accessed 15 October 2012.

3. Miller, William Ian. 1997. The anatomy of disgust. Cam-bridge: Harvard University Press.

4. Nussbaum, Martha. 2004. Hiding from humanity: disgust,shame and the law. New Jersey: Princeton University Press.

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