Common ingroup identity refers to an individual’s cognition of belonging to a particular social group, leading to emotional and interest-based identification with that group. ¹¹ The Common Ingroup Identity Model (CIIM) posits that when individuals recategorize members of different groups (including ingroups and outgroups) into a single, more inclusive superordinate group, their negative attitudes towards former outgroup members may decrease, and positive emotions may extend to these individuals. ¹¹ This adjustment in social categorization can improve intergroup relations and reduce negative stereotypes and prejudices by increasing perceptions of commonality and similarity while decreasing perceptions of difference. ¹²

Based on CIIM, we propose that perspective-taking may facilitate the recategorization process central to common ingroup identity formation, thereby potentially reducing weight stigma. Perspective-taking encourages individuals to view situations from the standpoint of outgroup members, promoting recognition of shared experiences and characteristics. ¹³ This recognition could lead to a more inclusive categorization where both the self and individuals with obesity are perceived as part of a larger, superordinate group (e.g., “people” or “students”) rather than as members of distinct weight-based groups. Through this process, perspective-taking can improve overall evaluations of minority groups, reduce perceptions of ingroup typicality, and alter the tendency to evaluate outgroups using internal standards. ¹⁴ These effects align with the CIIM’s emphasis on reducing intergroup bias through recategorization, potentially reducing the salience of weight-based group boundaries and promoting a sense of “we” rather than “us” and “them”. ¹¹ Stephan and Finlay ¹⁵ further argue that viewing issues from another group’s perspective can enhance the perception of common humanity and shared destiny, thereby increasing common ingroup identity.

As a result of this shift in social categorization, individuals may develop more positive evaluations of people with obesity. This occurs because the positive biases typically reserved for ingroup members may extend to those who were previously considered outgroup members but are now included in the superordinate group. ¹⁶ In other words, as people with obesity become perceived as part of the broader ingroup, the favorable attitudes typically associated with ingroup membership may be applied to them as well.

Therefore, perspective-taking may not only directly reduce negative attitudes towards individuals with obesity but may also indirectly improve weight stigma by enhancing common ingroup identity. ^{14, 17} This dual pathway - direct attitude change through perspective-taking and indirect change via enhanced common ingroup identity - provides a theoretical framework for understanding how perspective-taking interventions might effectively reduce weight stigma.

Despite these theoretical expectations, empirical research on the effectiveness of perspective-taking in reducing weight stigmatizing attitudes has yielded mixed results. The limited existing studies suggest that perspective-taking may not always effectively reduce negative stereotypes about individuals with obesity. For instance, Gapinski et al. ¹⁸ and Teachman et al. ¹⁹ found that while perspective-taking could evoke empathy towards individuals with obesity among participants, this empathy did not necessarily translate into reduced negative attitudes. Paradoxically, empathy sometimes aroused participants’ fear of obesity, leading to discomfort and aversion, thereby potentially nullifying the sympathy towards the stigmatized group. These findings indicate that in the context of weight stigma, perspective-taking may not consistently yield positive outcomes and might even exacerbate negative emotions in some cases.

While research specifically applying perspective-taking to weight stigma remains scarce, studies in other domains of stigma have shown promising results. For example, Martinez et al. ²⁰ found that participants who imagined themselves as individuals with depression and recorded how antidepressants changed their lives showed significantly improved attitudes towards people with depression. In the realm of racial stigma, Shih et al. ²¹ conducted an intervention experiment where participants were asked to experience the role of Asian individuals, resulting in significantly improved attitudes towards Asian groups.

Furthermore, several studies have examined the association between perspective-taking and common ingroup identity. Cohen and Insko ²² posited that perspective-taking could be an effective method for reducing prejudice and optimizing intergroup relations. They argued that perspective-taking can enhance emotional connections between groups and promote the perception of common humanity and shared destiny with outgroups. In support of this idea, Sassenberg and Matschke ²³ demonstrated that students participating in international exchange programs increased their identification with the host country through perspective-taking. Sarge et al. ²⁴ conducted a public stigma intervention experiment focusing on Autism Spectrum Disorder (ASD). Their findings revealed that perspective-taking not only enhanced participants’ emotional concern, helping intentions, and willingness to volunteer towards individuals with ASD, but also led to an increased sense of connection with this group. This increased connection was interpreted as evidence of a strengthened common ingroup identity, where participants began to view individuals with ASD as part of their broader social group rather than as outgroup members. Additionally, Andrighetto et al. ²⁵ discovered that frequently and deeply experiencing the plight of outgroup members could reduce conflicts between ingroups and outgroups and enhance intergroup understanding and identification among Kosovo Albanian students.

The relationship between common ingroup identity and the reduction of stigma is particularly noteworthy. Gaertner et al. ²⁶ argued that enhancing common ingroup identity could further motivate individuals to reduce negative stereotypes and prejudices towards outgroups, thereby improving weight stigmatizing attitudes towards others. Empirical research by Kunst et al. ²⁷ demonstrated that enhancing common ingroup identity could effectively reduce resource allocation bias between majority groups and immigrant groups. When a common ingroup was emphasized, majority group members were more likely to accept immigrants as valuable group members and support their equal status.

A study by Brochu et al. ²⁸ demonstrated how emphasizing a shared group identity can mitigate weight bias. In their study, the researchers manipulated common ingroup identity by highlighting shared identities such as “job seekers” or “professionals” that encompassed both individuals with and without obesity. They found that when participants identified with these inclusive categories, they became more aware of workplace discrimination faced by individuals with obesity, which crucially led to a significant reduction in weight bias towards overweight and obese individuals. In a follow-up experiment with over 200 American participants, Brochu et al. further validated these findings. The experimental group, where weight discrimination was highlighted and common ingroup identity was emphasized, showed significantly reduced weight bias compared to the control group. These findings provide strong empirical support for the effectiveness of common ingroup identity in reducing weight stigma. By fostering a sense of shared group membership, the study demonstrated that individuals were more likely to empathize with and show less bias towards people with obesity, directly illustrating the potential of common ingroup identity as an intervention strategy for weight stigma reduction.

In summary, although no previous research has simultaneously explored the associations between perspective-taking, common ingroup identity, and weight stigma, based on the theoretical guidance of CIIM ¹¹ and existing empirical research results, we propose that perspective-taking should help reduce individuals’ weight stigma towards others. Moreover, common ingroup identity may play a mediating role in this relationship. The research questions of this study include: a.

Is perspective-taking effective in reducing weight stigma?

Based on these research questions and the reviewed literature, we propose the following hypotheses: H1:

Participants engaged in a perspective-taking task will show lower levels of weight stigma compared to those in a control condition.

This study employed a mixed experimental design with perspective-taking (experimental vs. control) as a between-subjects factor and measurement time (pre-test vs. post-test) as a within-subjects factor. A single-blind procedure was implemented, with participants unaware of their group assignment.

Participants were recruited from a university in China. Data collection took place between September and December 2023. The sample comprised 202 university students (N = 202) who completed the study and received 10 RMB as compensation. Participants were randomly assigned to either the experimental group (n = 102; 32 males, 70 females; age: M = 21.49 years, SD = 2.36) or the control group (n = 100; 29 males, 71 females; age: M = 21.45 years, SD = 1.74).

Sample size was determined using G*Power. ²⁹ Based on the study design (a 2×2 mixed ANCOVA with pre-test scores as a covariate; see Data Analysis section for details), we calculated that a minimum of 128 participants would be required to detect a medium effect size ( f = 0.25) with 80% power at α = 0.05. Our final sample of 202 participants exceeded this requirement, ensuring adequate statistical power. The study was approved by the Jiangxi Psychological Consultant Association, with Protocol No/IRB No: JXSXL-2021-J99. The approval was granted on July 10, 2022.

Participants in both the experimental and control groups completed the tasks individually. At the beginning of the task, all participants completed the weight stigma scale and a demographic survey as a pre-test, followed by a ten-minute break. Subsequently, participants in both groups read their respective experimental materials. The materials included descriptions of daily life, emotional experiences, and social interactions of individuals with obesity, emphasizing negative evaluations and emotional responses experienced in public settings.

For the experimental group, the perspective-taking manipulation encouraged participants to think and perceive from the viewpoint of an individual with obesity. They received the following instructions: “You will now read a passage. As you read, please imagine yourself as the protagonist in the material. Try to put yourself in their shoes and experience their thoughts and inner feelings.” After reading, they were further instructed: “Imagine you are the protagonist. Considering what the protagonist has experienced, how do you feel? What would you like to say or do? What are your plans for the future? Please write your responses, taking 5 minutes and using at least 100 words.”

Control group participants read the same material but were instructed to remain objective: “You will now read a passage. We will test your memory of time and place cues. Please try to remain objective while reading and pay close attention to the plot and time points in the material.” After reading, they were asked to objectively describe the life of the individual with obesity: “Please summarize the events that happened to the protagonist in chronological order from a third-person perspective. Take 5 minutes and write at least 100 words.”

Immediately after completing the writing task, all participants completed the post-test, which included measures of perspective-taking engagement, the weight stigma scale, and the common ingroup identity scale.

To assess the level of perspective-taking engagement, participants in both groups answered two questions during the post-test: “To what extent did you put yourself in the protagonist’s position while completing the task?” and “How deeply did you empathize with the protagonist’s feelings while completing the task?” Responses were recorded on a 5-point Likert scale, where 1 represented “Not at all,” 3 represented “Moderately,” and 5 represented “Completely.” The McDonald’s omega coefficient for these two items across both groups was 0.75, indicating acceptable internal consistency. The sum of scores on these two items was used as a measure of perspective-taking engagement, serving as a manipulation check for the experimental intervention.

The Anti-Fat Attitudes Test (AFAT), developed by Lewis et al. ³⁰ is widely used to measure public attitudes towards obesity and was employed in this study to assess weight stigma. The AFAT comprises three factors: Physical/Romantic Unattractiveness (views on the personality and external attractiveness of individuals with obesity), Weight Control/Blame (eating habits and factors influencing weight change), and Social/Character Disparagement (personal emotional reactions towards individuals with obesity). The AFAT has demonstrated high internal consistency, with Cronbach’s α coefficients typically ranging from 0.80 to 0.90. ³⁰ Additionally, the AFAT has shown good test-retest reliability and criterion-related validity. ³¹ Higher total scores on the AFAT indicate stronger negative attitudes towards individuals with obesity. In the present study, the omega coefficient was 0.95 for both pre-test and post-test, indicating excellent internal consistency reliability.

To measure participants’ common ingroup identity, we adapted two items from the Common Ingroup Identity Scale developed by Ufkes, Dovidio, and Tel. ³² The items were adjusted to measure common ingroup identity among university students: “I am very happy to be a member of the university student group that includes students of all body types in our country” and “Being part of the university student group that includes students of all body types in our country is an important part of my identity.” Responses were recorded on a 7-point Likert scale, where 1 represented “Strongly disagree” and 7 represented “Strongly agree.” The omega coefficient for these items was 0.70 for both pre-test and post-test, indicating acceptable internal consistency.

Data were analyzed using jamovi, ³³ which should be open access. First, we conducted descriptive statistics for all variables. To assess the effectiveness of the perspective-taking manipulation, we conducted an independent samples t-test. The experimental condition (perspective-taking vs. control) served as the independent variable, and participants’ self-reported perspective-taking engagement scores served as the dependent variable.

To examine differences in post-test weight stigma between the perspective-taking and control groups while controlling for pre-test scores, we conducted an analysis of covariance (ANCOVA). The experimental condition served as the independent variable, post-test weight stigma scores as the dependent variable, and pre-test weight stigma scores as the covariate.

To investigate the role of common ingroup identity in the relationship between perspective-taking and weight stigma, we conducted a mediation analysis. Prior to this analysis, zero-order correlations were examined. For the mediation model, the perspective-taking condition was dummy-coded (1 = experimental group/perspective-taking, 2 = control group). Common ingroup identity served as the mediator variable, and post-test weight stigma as the outcome variable. Pre-test weight stigma scores, gender, and age were included as covariates. The analysis was performed using the JAMM module in jamovi, with 5000 bootstrap resamples and 95% confidence intervals.

While this study provides preliminary evidence for the significant positive impact of perspective-taking on reducing weight stigma attitudes among university students through a mixed experimental design, several limitations should be acknowledged. The relatively short intervention period may not have fully captured the long-term effects on reducing weight stigma. Future research could benefit from extended intervention durations or more in-depth perspective-taking tasks to strengthen the intervention’s impact. Additionally, the brief interval between pre- and post-tests, despite our use of ANCOVA to control for pre-test influences, suggests that longer intervals between assessments could further refine the experimental manipulation in future studies. The absence of a significant mediating effect of common ingroup identity warrants further investigation, potentially through alternative experimental designs or larger sample sizes to validate this mediating mechanism. Moreover, exploring other potential mediating variables, such as emotional resonance or self-reflection, in the relationship between perspective-taking and weight stigma represents an important direction for future research. These refinements and expansions of the current study could provide more comprehensive insights into the mechanisms underlying the reduction of weight stigma through perspective-taking interventions.