This article highlights the social concept of pollution or impurity and its use as a justification for discrimination and exclusion. First, the history of the concept of pollution is reviewed. Second, a development of two scales measuring the tendency towards pollution related thoughts, the Purity Orientation–Pollution Avoidance (POPA) Scale and the Avoidance of Resentment Scale (ARS), is explained. Third, an experimental study using these scales is introduced. Then, the relationships between four purity/pollution factors and exclusive behaviors were investigated using structural equation modelling. The results revealed that the pollution avoidance tendency enhances anxious feeling towards immigrants, but this relationship is mediated by a type of belief that “natural things are the best,” which stems from pollution avoidance motivation. Finally, this article summarizes how the concept of pollution can cause discriminations and exclusions, and discusses solutions for the problem.

This paper reviews the previous work on disgust from the perspective of moral judgment. Shweder et al. (1997) proposed that morality consists of three dimensions: autonomy, community, and divinity. This interpretation of morality serves as one’s rationale and/or standards in moral judgment. Graham et al. (2011) extended Shweder’s idea and developed it as Moral Foundations Theory (MFT). The purity foundation of the MFT corresponds to the divinity dimension of Shweder’s theory and is found to evoke disgust. What kind of behavior people should judge as morally wrong in terms of the purity foundation is shared among ingroup members, which makes them bound together; that is a social function of morality. Accordingly, their moral judgment leads violators to be socially excluded. Although understanding the purity foundation helps researchers clarify how ingroup members are eventually excluded, cultural differences in the concept of purity can exist, such as the unique purity orientation among the Japanese. In addition, this paper addresses such concepts relevant to social exclusion as moralization and moral elevation. The theoretical and practical findings from research on moral judgment will contribute to the better understanding of the mechanism of disgust being evoked and social exclusion being processed.

Potential bullying involvement, defined as indirect reinforcement of bullying and contextualized teasing, was explained by individual sensitivity to envy and classroom orientations of the cultural self, using multi-level analysis. A survey was conducted among 1,205 Japanese junior high school students in 39 classrooms. Results confirmed that at the classroom level, potential bullying involvement was explained by malicious envy and classroom interdependence, and that malicious envy was in turn explained by classroom interdependence. A parallel survey of 39 homeroom teachers on classroom disorganization found that their ratings did not track classroom interdependence or malicious envy.

This study focuses on disgust evaluation as a factor promoting social exclusion behavior toward a specific group and its members. The study included 40 undergraduate students (mean age＝20.05, SD＝1.12) who were evaluated for the process of acquiring disgust evaluations of a group and its members and the possibility of changing this evaluation. Experiments conducted from the perspective of evaluative conditioning validated the establishment of the evaluative conditioning of disgust for a group symbol paired with disgust stimuli. Thus, a higher-order evaluative conditioning procedure revealed that the evaluations of members categorized in the disgust group were relatively worse. These effects were observed only under conditions where pathogen primes were presented in advance, thereby indicating that the behavioral immunity system may be involved in the acquisition of disgust evaluation of specific group members. The in-group recategorization procedure did not improve this evaluation. We discuss the possible interpretations of these results and proposed measures to manage with social exclusion behavior.

In 2017 and 2019, two surveys were conducted to clarify the changes and characteristics of target groups of exclusionism among the Japanese people. A survey to compare between the Chinese, South Koreans, North Koreans, and Taiwanese as the target groups, was added in 2020. In Survey 1 (2017) and Survey 2 (2019), participants who were 20 to 69 years old were asked to recall a group that they feel most dislike. Approximately 70％ of the participants in both surveys were able to describe a certain dislike group. In Survey 1, the types of target groups were the members of Japanese new religions, nationals of three neighboring countries (China, South Korea, and North Korea), and the members of Islamic State, in descending order. In Survey 2, the frequencies of the nationals of three Asian countries increased, due to an increase in the numbers of responses choosing South Korea. Consequently, the order of first to third place was switched to three neighboring countries, Japanese new religions, and political parties. There were some gender differences among the participants with their choices of target groups, but no significant differences by age groups were indicated. Negative and positive emotions toward the countries and the tendency to exclude them were significantly reduced between Survey 1 and 2. In Survey 3 (2020), North Korea, China, South Korea, and Taiwan were evaluated negatively in this order, but there were no significant differences in exclusionary thinking and behaviors among the countries. Based on these outcomes, the characteristics of exclusionism among the Japanese in the survey period were discussed.

The purpose of this study was to contribute to the planning of solutions and preventive measures against exclusionary behaviors targeting specific minority groups. Focusing on disgust and related emotions, which have rarely been addressed in previous research, the authors developed a hypothetical comprehensive model that explains the psychological processes behind social exclusion, starting from information input, attention bias, cognitive evaluation, emotions, exclusionary attitude, and such behavior. In order to validate the model, we conducted a survey on impressions of Northeast Asian countries with 1068 participants, based on previous studies (Kawano & Nakamura, 2021). As a result of the analysis of covariance for the structural equation model reflecting the hypothetical model, it was confirmed that the model shows the sufficient fit to the date as a comprehensive psychological process model, and we were able to provide guidelines for contributing to the planning of solutions to problems and preventive measures based on the psychological processes behind social exclusion.

From the perspective that disgust is deeply involved in exclusion, I commented on six papers in this special issue. In the first sense, disgust is a food-related emotion that rejects harmful foods. However, with cognitive development, things that are offensive to the self and the group (society, culture) to which the self belongs evoke disgust. Exclusion is often a conscious and deliberate action taken against out-group members who are harmful or expected to be harmful to the in-group and its members. Therefore, a high level of cognitive-emotional process is involved in its occurrence. Disgust plays a central role in this process. Finally, I mentioned the possibility of realizing a multicultural society without exclusion.