A Developmental Perspective on Disgust: Implications for Obsessive-Compulsive Disorder

Evolutionary psychology of entomophobia and its implications for insect conservation

Many people, especially those living in developed countries, exhibit irrational negative feelings (e.g. fear, disgust, and aversion) toward insects. This so-called 'entomophobia' has often been suggested as a key contributing factor to the ongoing global decline in insects. However, this topic has not been well-investigated. From this point of view, we discuss the formation processes of entomophobia and its consequences from an evolutionary psychological perspective. Adopting the concept of the behavioral immune system, we suggest that the negative responses toward insects exhibited by modern people are driven by a series of emotional, cognitive, and behavioral traits that evolved to avoid infectious diseases. We then provide several strategic recommendations for mitigating the prevalence of entomophobia and a roadmap for better understanding how individual-level entomophobia can influence insect conservation. Understanding the human psychological dimension behind the ongoing decline of insects will provide useful insight on how best to mitigate this decline.

Why do people vary in disgust?

People vary in the degree to which they experience disgust toward—and, consequently, avoid—cues to pathogens. Prodigious work has measured this variation and observed that it relates to, among other things, personality, psychopathological tendencies, and moral and political sentiments. Less work has sought to generate hypotheses aimed at explaining why this variation exists in the first place, and even less work has evaluated how well data support these hypotheses. In this paper, we present and review the evidence supporting three such proposals. First, researchers have suggested that variability reflects a general tendency to experience anxiety or emotional distress. Second, researchers have suggested that variability arises from parental modelling, with offspring calibrating their pathogen avoidance based on their parents' reactions to pathogen cues. Third, researchers have suggested that individuals calibrate their disgust sensitivity to the parasite stress of the ecology in which they develop. We conclude that none of these hypotheses is supported by existing data, and we propose directions for future research aimed at better understanding this variation.

This article is part of the Theo Murphy meeting issue ‘Evolution of pathogen and parasite avoidance behaviours’.

Disgust and the rubber hand illusion: a registered replication report of Jalal, Krishnakumar, and Ramachandran (2015)

Heightened experience of disgust is a feature of obsessive-compulsive disorder (OCD), particularly contamination-related OCD (C-OCD). Previous studies of the rubber hand illusion (RHI) reported that the sense of body ownership is related to the interaction between vision, touch, and proprioception. One recent study demonstrated a link between the RHI and disgust, suggesting that there is an interaction between these three perceptual modalities and disgust (Jalal et al., PLOS ONE 10:e0139159, 2015). However, there have been no direct replications of this initial study. We therefore performed a direct replication of Jalal et al.'s (PLOS ONE 10:e0139159, 2015) study. We examined 133 participants (based on a power analysis) to determine whether placing contamination-related stimuli on a rubber hand causes OCD-like disgust among healthy participants experiencing the RHI. That is, we tested whether Japanese participants experience more intense disgust when the rubber hand and the participant's hidden hand are stroked synchronously than when stroked asynchronously, in order to replicate and examine the cross-cultural validity of this effect. The main finding of the original study by Jalal and colleagues was successfully replicated in a large sample. Some inconsistencies in one of the control procedures exploring coldness sensations during the RHI were found, which could possibly be due to cross-cultural differences or the improved statistical power of the present study. Based on the present replication study, we conclude that an intervention using the RHI as proposed by Jalal et al. (PLOS ONE 10:e0139159, 2015) might potentially be useful for the treatment of OCD following replications in clinical OCD populations. Preregistration details: This study was preregistered with Cognitive Research: Principles and Implications. The Authors' protocol received in-principle acceptance on 31 March 2017. The preregistered protocol is available here: 10.6084/m9.figshare.6217295.