The domains of disgust and their origins: contrasting biological and cultural evolutionary accounts

Psychological Review, 2013

Interest in and research on disgust has surged over the past few decades. The field, however, still lacks a coherent theoretical framework for understanding the evolved function or functions of disgust. Here we present such a framework, emphasizing 2 levels of analysis: that of evolved function and that of information processing. Although there is widespread agreement that disgust evolved to motivate the avoidance of contact with disease-causing organisms, there is no consensus about the functions disgust serves when evoked by acts unrelated to pathogen avoidance. Here we suggest that in addition to motivating pathogen avoidance, disgust evolved to regulate decisions in the domains of mate choice and morality. For each proposed evolved function, we posit distinct information processing systems that integrate function-relevant information and account for the trade-offs required of each disgust system. By refocusing the discussion of disgust on computational mechanisms, we recast prior theorizing on disgust into a framework that can generate new lines of empirical and theoretical inquiry.

Proceedings of The Royal Society B: Biological Sciences, 2004

Disgust is a powerful human emotion that has been little studied until recently. Current theories do not coherently explain the purpose of disgust, nor why a wide range of stimuli can provoke a similar emotional response. Over 40 000 individuals completed a web-based survey using photo stimuli. Images of objects holding a potential disease threat were reported as signif icantly more disgusting than similar images with little or no disease relevance. This pattern of response was found across all regions of the world. Females reported higher disgust sensitivity than males; there was a constant decline in disgust sensitivity over the life course; and the bodily fluids of strangers were found more disgusting than those of close relatives. These data provide evidence that the human disgust emotion may be an evolved response to objects in the environment that represent threats of infectious disease.

Evolutionary developmental psychology typically utilizes an evolutionary lens to explain various phenomena that occur throughout development. In this paper, I argue that the converse is also important: Developmental evidence can inform evolutionary theory. In particular, knowledge about the developmental origins of a psychological trait can be used to evaluate theoretical claims about its evolved function. I use the emotion of disgust as a case study to illustrate this approach. Disgust is commonly thought to be a behavioral adaptation for avoiding the ingestion of pathogens. Given this claim, disgust should be expected to develop at a time when humans are especially vulnerable to the dangers of ingesting pathogens, during the immediate post-weaning period from about 3 to 5 years of age. Despite a strong selective pressure at this point in development, research has suggested that the emotion of disgust and the recognition of the "disgust face" do not reliably emerge until later in ontogeny, at 5 years of age or after. Given the late developmental appearance of disgust, I re-evaluate claims about its adaptive role.

Journal of Personality and Social Psychology, 2009

What is the function of disgust? Whereas traditional models have suggested that disgust serves to protect the self or neutralize reminders of our animal nature, an evolutionary perspective suggests that disgust functions to solve three qualitatively different adaptive problems related to pathogen avoidance, mate choice, and social interaction. We investigated this three-domain model of disgust across four studies and examined how sensitivity to these functional domains relates to individual differences in other psychological constructs. Consistent with our predictions, factor analyses demonstrated that disgust sensitivity partitions into domains related to pathogens, sexuality, and morality. Further, sensitivity to the three domains shows predictable differentiation based on sex, perceived vulnerability to disease, psychopathic tendencies, and Big Five personality traits. In exploring these three domains of disgust, we introduce a new measure of disgust sensitivity. Appreciation of the functional heterogeneity of disgust has important implications for research on individual differences in disgust sensitivity, emotion, clinical impairments, and neuroscientific investigations.

Evolutionary Behavioral Sciences

We thank Julie Fitness for comments that improved the manuscript and Hella Peter for providing the video included in the electronic supplementary material. We are also grateful to each of the primate experts who took the time to complete our survey.

Psicothema , 2013

Background. Disgust is, at its core, an emotion that responds to cues of parasites and infection, likely to be evolved to protect human organism to the risk of disease. Interestingly, a growing body of research implicates disgust as an emotion central to human morality. The fact that disgust is associated with appraisals of moral transgressions and that this emotion influences moral judgments supposes a remarkable puzzle: Why an emotion that originally functions in the domain of infectious entities does become such a good candidate to play the role of a moral arbiter? The aim of the present review is to clarify the nature of the relationship between disgust and morality. Method. First, we examine the relevant features of disgust in order to explore whether disgust’s phenomenology favors its implementation as a defensive mechanism against offensive social entities. Second, we critically review the most striking findings about the effects of disgust on moral judgments. Results. The revisited analysis of the literature strongly suggests a bidirectional causal link between disgust and moral cognition. Conclusions. We propose that the particular phenomenology of disgust (which involves a sense of offensiveness and rejection) favored the co-adaptation of this emotion to the moral domain.

Genes, Brain and Behavior, 2018

Disgust can be thought of as an affective system that has evolved to detect signs of pathogens, parasite and toxins as well as to stimulate behaviors that reduce the risk of their acquisition. Disgust incorporates social cognitive mechanisms to regulate exposure to and, or anticipate and avoid exposure to pathogens and toxins. Social cognition entails the acquisition of social information about others (ie, social recognition) and from others (ie, social learning). This involves recognizing and assessing other individuals and the pathogen/parasite/contamination/toxin threat they pose and deciding about when and how to interact with and, or avoid them. Social cognition provides a frame-work for examining the expression of disgust and the associated neurobiological mechanisms. Here, we briefly consider the relations between social cognition and pathogen/parasite/toxin avoidance behaviors. We briefly discuss aspects of: (1) the odor mediated social recognition of actual and potentially infected individuals and the impact of parasite/pathogen threat on disgust mate and social partner choice; (2) the roles of "out-groups" (strangers, unfamiliar individuals) and "in-groups" (familiar individuals) in the expression of disgust and pathogen avoidance behaviors; (3) individual and social learning of disgust and empathy for disgust; (4) toxin elicited disgust and anticipatory disgust; (5) the neurobiological mechanisms, and in particular the roles of the nonapeptide, oxytocin and estrogenic mechanism associated with social cognition and the expression of disgust. These findings on the social neuroscience of disgust have a direct bearing on our understanding of the roles of disgust in shaping human and nonhuman social behavior.

Biology & Philosophy, 2015

An overview of current theories (including mine) on sensory and interpersonal disgust. This is the first and only paper that I know of that attempts to explain why humans are the only species known to experience disgust.