An Examination of the Social Identity Model of Collective Action in the Context of Vietnam

This study was conducted to examine the applicability of the social identity model of collective action [SIMCA] in the context of Vietnam. Specifically, we assessed the predictive powers of moral conviction, politicized identity, group-based anger, and group efficacy on people’s intentions to engage in collective action in a situation where people from three communes of Hanoi blocked garbage trucks to enter a waste treatment complex located in this area.


INTRODUCTION
In recent decades, Vietnam has witnessed an increasing number of social protests relating to land [1, 2] and environmental disputes [3,4]. Many of the initially peaceful collective struggles have transmuted into small or mediumscale violent confrontations between protesters and authorities, causing social unrest [1 -3]. In order to find more amicable solutions to these social protests, it is essential to dig deeper into the antecedents of collective action pertaining to land and environmental disputes in the Vietnamese context. However, there is little research on this topic. Based on Gustave Le Bon's classical theory [5], the government and some domestic social scientists tend to equate collective action with crowd behavior [6 -8]. They come to the conclusion that collective action is unconscious, instinctive, thoughtless, and antisocial. Moreover, they argue that individuals engaging in collective action are lured by hostile forces to overthrow the leading role of the state and the Communist Party of Vietnam [1,2]. By putting people at odds with the government, this viewpoint exhorts authorities to adopt violent measures to deal with people's collective action. This status quo raises a demand for a new approach to collective action in Vietnam.
In social psychology, collective action is defined as any behavior performed by individuals to maintain and enhance the interests and relative status of the group to which they psychologically belong [9]. Many socio-psychological theories have been formulated to ascertain what motivates individuals to engage in collective action. Among these, with many supporting evidence, the Social Identity Model of Collective Action (SIMCA) is the most prominent one. This model hypothesizes that individuals' participation in collective action could be predicted by their experience of injustice, group efficacy, social identity, and moral conviction [10 -12]. These four factors are believed to be universal [13]. However, since the SIMCA is primarily based on theories and empirical evidence from Western cultures, its use to explain collective action in non-Western contexts needs to be ensured circumspectly. Prior studies suggested that Asian participants exhibited patterns of collective action that are different from the expectation of SIMCA [13 -16]. As an Asian nation with certain unique cultural and political characteristics, Vietnam is expected to show some differences from Western countries in applying the SIMCA to explain collective action.
The study was conducted to examine the applicability of the SIMCA in the context of land and environmental disputes in Vietnam. In terms of theoretical contribution, research findings were expected to be the foundation for supporting or challenging the SIMCA's applicability to a non-Western culture. By doing so, they could expand our understanding of cultural differences in participating in collective action. In practical terms, research findings would be the scientific basis for developing constructive solutions to land and environmental, protests in Vietnam.

The Social Identity Model of Collective Action
The SIMCA was the result of an effort to integrate theories and empirical evidence in socio-psychological literature to find out variables that can explain individuals' participation in collective action [8 -12]. The SIMCA proposed that collective action could be predicted by perceived injustice i.e., individuals' perception and feelings of injustice towards their group, belief in the group efficacy i.e., the confidence of individuals in the ability of group members to succeed in acting for the benefit of the group, social identity i.e., the extent to which individuals psychologically connected to the group or consider themselves members of the group. Injustice and group efficacy were further hypothesized as mediators of the relationships between social identity and collective action. The model then integrated moral conviction i.e., a strong and absolute stance, based on moral beliefs, of individuals on situations or events relating to their group as a key energizer for collective action [11]. In other words, the model postulated that moral conviction had an indirect effect on collective action via perceived injustice and group efficacy.

The Social Identity Model of Collective Action in the Asian Context
Previous studies examining the predictive power of the SIMCA on the collective action in Asian countries suggested that the hypothesized relationships among the variables of this model could be moderated by cultural factors [13 -16]. The two most salient aspects in Asian cultures that have impacts on the SIMCA are collectivism and power distance.
A study reported that even though having the desire to take collective action against sexism, Japanese female students chose more indirect solutions [15]. Besides, there was a rare null relationship between social identification and collective action intentions among Indonesia who belonged to a lowstatus group [14]. Instead of participating in collective action, they were inclined to seek social connections to protect their well-being. The common reason for those situations was that the cultural appreciation of maintaining within-and betweengroup harmony might discourage collective action, which could be regarded as threatening to social structures [13 -16]. Besides, several studies indicated that only individuals who had a tendency toward individualism (i.e., possessing more independent self-concept or more internal locus of control and caring less for face) could overcome that cultural inhibition to engage in collective attempts [15,16].
A study with a Chinese sample reported that for those who belonged to a lower-status group, there was no significant relationship between anger at group injustice and collective action intentions [17]. The identical relationship was also established among Filipino and Japanese males in relation to a sexist scenario [18]. Together with the tendency to avoid collective action of Indonesian low-status group mentioned above [14], these results supported the notion that a high level of power distance in Asian cultures offered no or little hope and scope for social change as inequalities (e.g., sexism and power structure) were legitimized.
In conclusion, collectivism and power distance in Asian countries are likely to inhibit individuals' willingness to participate in collective action, regardless of individuals' experience of injustice, group efficacy, and group identification, resulting in cultural differences between European and Asian countries in the psychological processes of collective action.

The Collective Action Relating to Land and Environmental Disputes in the Vietnamese Context
Given the above conclusions and the fact that Vietnam has a collective culture and high level of power disparity [19], one using the SIMCA to elucidate the collective action in Vietnam must expect to obtain results that are similar to what has been found from previous studies within Asian contexts. However, extant evidence implies that the Vietnamese context may witness some consistencies with and deviances from other countries in terms of research findings relating to the SIMCA's explanation of collective action.
Several studies have shown that Vietnamese people are typically engaged in collective action to protest against local authorities' unfair treatment pertaining to land confiscation and compensation, and/or compensation for environmental damages [1 -4]. A survey reported that more than 83% of citizens would take action if they encountered one of these two problems [20]. Moreover, in some cases, especially when the local government threatens and uses coercive measures toward peaceful protest, people may become angry and take part in non-normative, or even violent, collective action [1 -3]. Thus, these inputs echo the SIMCA's hypothesis of a positive relationship between perceived injustice, or group-based anger at group injustice, and the involvement in collective action [10].
Intriguingly, also according to the survey above, about 50% of the respondents would accept an unjust land compensation if there was a corruption of their local government [20]. Regarding environmental pollution, about 33% of them would give up claiming for compensation if they detected a lack of integrity among their local authorities. Although aimed at individual problem-solving efforts, these statistics somewhat suggested that mistrusting a group's ability to produce social changes might reduce the probability that individuals participated in collective attempts to reclaim their rights and interests.
Vietnamese people highly value their social groups and identities. Among these, the local identity is the most prominent and plays an important role in the lives of Vietnamese people, especially in rural areas. This local identity is built on not only common habitat but also their solidarity in coping with communal adversities (e.g., floods and wars). Therefore, given that land and environmental inequities in Vietnam often occur at the scale of one or more communes, we expect that a group identity to be formed among the residents of these areas based on their shared issues. A qualitative analysis has pointed out that Vietnamese villagers' social protests usually have no association or cooperation because they have distinct problems, goals, and perpetrators [1].
Another study further noted that if several protests shared a common goal of opposing a particular local government, they would be likely to unite [2]. These two tendencies reflect, to some extent, individuals' awareness of group identity while participating in collective action. Thus, the SIMCA's notion that group identity is a predictor of collective action [10] may be supported by the data collected from the Vietnamese context.
A study showed that many of the Vietnamese people's social struggles for justice and fairness in land and environmental management were based on not only current laws but also on people's moral beliefs [1]. The tendency of people to absolutize their moral convictions [13] even made them reject the laws allowing the state to unilaterally confiscate their land. To the villagers, unilateral land acquisition is unfair as it deprives them of their livelihoods. Furthermore, they insist on the ownership of the land that their families participated in protecting during the war. Thus, consistent with the SIMCA [10], these results suggested a positive relationship between moral conviction and collective action.
Considering previous research findings relating to Asians, there are two possible reasons why these results are inconsistent with existing evidence of land-and environmentrelated collective action in Vietnam. First, the inhibiting effect of the appreciation of interpersonal and inter-group harmony on collective action [13 -16] may not be applicable to conflicts between people and local government. Collective action in this situation may even reflect the solidarity among individuals in the same village or commune. Second, although Vietnam is perceived as having a great power disparity [20], the collective action of those people, who often perceive themselves as having the lowest social status, still occasionally bring about certain improvements [1, 2], not completely depriving the lowstatus group of the hope for achieving social changes by group efforts [13,14].

The Present Study
Based on the hypotheses proposed by the SIMCA [10, 11] and empirical evidence presented above, we expected that in the context of land and environmental disputes in Vietnam, group-based anger, group efficacy, politicized identity, and moral convictions would be the positive predictors of people's collective action intentions. In addition, group-based anger and group efficacy were hypothesized to be mediators in the relationship between politicized identity and collective action intentions. Finally, group-based anger, group efficacy, and politicized identity were also expected to fully explain the positive relationship between moral conviction and collective action intentions. This was the first study on the SIMCA conducted within the Vietnamese context. Our research findings were expected to contribute to the existing understanding of collective action in collectivistic cultures, highlighting the cultural divergence in terms of participating in collective action. In addition, the practical implications stemming from our research results should be useful for the construction of a more peaceful resolution for land-and environment-related social protests in Vietnam.

Participants and Procedure
The Nam Son Waste Disposal Complex (NSWDC), located among three communes, namely, Nam Son, Bac Son, and Hong Ky (NBH communes), Soc Son district, Hanoi, Vietnam. The waste landfill and incineration of this complex have caused serious negative impacts on the living environment of the residents in the surrounding areas, especially within a radius of 500 -1,000 meters. Dissatisfied with the pollution, residents of NBH communes have many times gotten together to prevent waste trucks from entering the NSWDC. Residents stopped this collective action only when the local government held a dialogue and had concrete solutions to meet residents' aspirations. By the end of July 2017, stemming from being attacked by the proliferation of flies, people again blocked the way to the waste disposal site to ask the government to formulate and implement a resettlement plan for people living within a 500 meters radius of the waste treatment area [where there are more than 2,000 households with a total, both agricultural and residential, area is about 396 hectares]. Since then, until July 2020, the residents stopped the garbage truck seven times due to grievances about the local government's delay in implementing the relocating and compensating policy for residents affected by the waste disposal area. To collect data for this study, we surveyed residents of NBH commune in early October 2019, three months after the fifth blocking of garbage trucks.
Research participants were 132 residents of NBH communes that were affected by NSWDC. They voluntarily participated in our study by signing a consent form. Males accounted for 43.90%, and mean age was 49.60, with a standard deviation of 13.74. The percentages of participants reporting primary school, secondary school, and university as their highest level of education were 10.60%, 43.90%, 24.20%, 18.20%, respectively. Four participants did not give information about their education level. Most of them were agricultural workers while 10.60%, 10.60%, and 8.30% of them were factory workers, freelancers, and housewives or retired, respectively. None of these demographic variables i.e., gender, education level, and occupations significantly predicted collective action intentions.

Moral Conviction
Participants were asked whether they supported or opposed the local authorities' delay in adequately compensating and relocating residents of NBH communes from areas affected by NSWDC. Based on items which had been used in Van Zomeren, Postmes, and Spears' study [11], moral conviction of those who declared the opposition to the local government's handling was measured with six items e.g., 'My opposition to this issue is a universal moral value that should apply everywhere in the world'. The participant rated each item with a seven-point Likert scale ranging from 1 = "totally disagree" to 7 = "totally agree". This Likert scale was also applied to the rest measures in this study. To examine whether these items reflected a common structure, we executed a principal axis factoring analysis with oblique rotation. One factor was extracted and explained 51.79% of the variance with factor loadings ranging from .59 to .86. The Cronbach's alpha of these items was .86.

Politicized Identity
Grounded on the scale had been proposed by van Zomeren, Postmes, Spears, and Bettache [21] to measure the extent to which participants identified themselves with social movement organization, we generated four items with the same purpose for this case e.g., 'I identify with locals who blocked roads leading to NSWDC'. A principal axis factoring analysis with oblique rotation showed that one item was not well explained by the underlying factor as its factor loading was only .18. After removing this item, one factor was extracted and predicted 78.85% of the variance with factor loadings ranging from .45 to .71. The Cronbach's alpha of the scale was .85.

Group-Based Anger
In the present study, the feelings of injustice were considered as reflected through group-based anger. Three items measuring how angry were participants, as a member of the social group, were generated e.g., 'As a resident of NBH communes, I feel angry because of this issue'. A principal axis factoring analysis with oblique rotation was conducted to identify the underlying construct among these items. Given the removal of the last item due to its low loading coefficient and communalities, one factor was extracted and 87% of variance was explained by this factor with factor loadings being above .93. The scale's Cronbach's alpha was .93.

Group Efficacy
Derived from van Zomeren, Postmes, and Spears' study [11], we measured participants' belief in group efficacy with four items e.g., 'As a resident of NBH communes, I think we can make the local authorities change'. A principal axis factoring analysis with oblique rotation indicated that after removing one item as it achieved low factor loading and communalities, the first three items reflected one common factor, which predicted 80.11% of their variance with factor loadings being above .86. The Cronbach's alpha for these items was .92.

Collective Action
The participant's intentions to participate in collective action were measured by four items that were adapted from van Zomeren, Postmes, and Spears' study [11] [e.g., 'I would participate in a demonstration to express my opposition']. The results obtained from principal axis factoring analysis with oblique rotation suggested to remove one item due to its low factor loadings and communalities. One factor was extracted, and it explained 70% of variance with factor loadings ranging from .61 to .94. The Cronbach's alpha of these items was .84.

Predicting Collective Action
Descriptive statistics and Pearson correlation coefficients between variables of interest are shown in Table 1. Overall, the variables weakly or moderately correlated with each other [r = .27 -.55]. As shown in the table, collective action significantly moderately correlated with all predictors from the SIMCA except for group efficacy [r = .10]. In addition, the correlation coefficient between politicized identity and group efficacy [r = .14] was not statistically significant. Noticeably, the mean of group efficacy was below five on a seven-point Likert scale. We performed a series of univariate and multivariate regression analyses with collective action as a dependent variable. The independent variables were the ones from the SIMCA. The results are presented in Table 2. Consistent with the results of correlation analysis, all variables, except group efficacy, could significantly predict collective action with the explainable proportion accounting from 18 to 22% of collective action's variance. Model 5 indicated that the regression coefficient of politicized identity on collective action decreased, suggesting the possibility of the partial mediating role of group-based anger for this association. Meanwhile, group efficacy continued to witness a nonsignificant regression coefficient on collective action. The collective action variance that could be predicted by this model was 27%. The figure for model 6 was 32% with the decline of both politicized identity and moral conviction's regression coefficients on collective action but they were still statistically significant. The results suggested a partial mediation model between these variables, which would not totally support the SIMCA.

Testing the Social Identity Model of Collective Action
To examine the extent to which the theoretically derived model of the SIMCA fit the data, we conducted a maximum likelihood path analysis by STATA/SE 14.0. The proposed model's goodness-of-fit indices did not support the hypothesis that it fit the data well, with χ 2 [2] = 11.08, p = .004, RMSEA = .185, CFI = .95, TLI = .72, SRMR = .04, based on the criteria suggested by Hu and Bentler [22]. All parameters, except for ones between politicized identity and group efficacy [β = -.04, p > .05], group efficacy and collective action [β = -.03, p > .05], and politicized identity and collective action [β = .23, p > .05], were statistically significant. Considering the fact that regression analysis did not support the full mediating function of politicized identity, group-based anger, and group efficacy in the relationship between moral conviction and collective action, we then tested the same model with an additional hypothetical direct effect of moral conviction on collective action, as shown in Fig. (1).   Goodness-of-fit indices showed that the model fit the data well, with χ 2 [1] = 1.42, p = .234, RMSEA = .056, CFI = .99, TLI = .98, SRMR = .02, following guidelines by Hu and Bentler [22]. Direct, indirect and total effects between variables in the model are reported in Table 3. The additional direct effect of moral conviction on collective action [β = .29, p < .01] was statistically significant. In addition, the direct effect of politicized identity on collective action [β = .17, p = .057] was ambiguously nonsignificant. This model predicted 32% of total variance of collective action. Politicized identity had no effect on group efficacy [β = -.06, p = .641]. Thus, moral conviction did not indirectly effect on group efficacy through politicized identity [β = -.04, p = .643]. The variance of group efficacy explained by these two variables was just 15%. Meanwhile, 41% of group-based anger's variance was directly and indirectly predicted by both moral conviction and politicized identity.

DISCUSSION
This study was conducted to assess the applicability of the SIMCA to the context of land and environmental disputes in Vietnam. To achieve this goal, we analyzed the data relating to the events in which residents of NBH communes blocked garbage trucks from entering NSWDC in Soc Son, Hanoi, Vietnam. These residents did so in order to require the local government to accelerate the progress of resettlement and compensation for households affected by NSWDC. Regression and path analyses indicated that, except for group efficacy, variables in the SIMCA significantly predicted collective action. Furthermore, politicized identity indirectly influenced collective action via group-based anger but not group efficacy. The moral conviction had both direct and indirect effects on collective action via group-based anger and politicized identity. These results demonstrated the similarities and differences between Vietnam and other countries, both Western and Asian, in terms of the psychological process of collective action.

The Pedictors of Collective Action
Univariate linear regression analyses pointed out that group-based anger, politicized identity, and moral conviction all significantly predicted collective action. Consistent with many previous studies [10], these results confirmed the hypothesis proposed by the SIMCA. Accordingly, the inadequate compensation and laggard resettlement progress as well as the pollution caused by NSWDC, made people feel that their social group was being treated unfairly, leading to their group-based anger. This negative emotion, in turn, motivated individuals to take part in collective struggles to protect their rights. This finding rejects the possibility that fearfulness or social class moderates the positive relationship between groupbased anger and collective action as found in several previous studies with low-status group's members as participants [17,23]. In addition, the more extent to which an individual identified with the politicized group in this case -a group of people from NBH communes blocking garbage -the more likely he or she would take part in collective action. This is in line with the notion that identification with a group, especially the politicized one that already has a course of action, will motivate individuals to protect the group's interests and relative status [10]. Finally, the more people believed that their moral view of the situation was absolute and universal; the more they were inclined to engage in collective action. This result confirms the hypothesis proposed by the SIMCA about the role of moral beliefs in collective action [11]. As indicated above, many social protests of Vietnamese people were based not only on official laws and the government's commitment but also on their own moral convictions. For example, in the field of land confiscation, people believe that they have ownerships of their land even if the law indicates that the state can unilaterally reclaim their land [1].
Notably, group efficacy, in this case, did not predict collective action. The belief in the ability of people from NBH communes to change adverse situations had no apparent connection to collective action. There are several ways to explain this result. First, there might be those who believed in the group so strongly that they felt the expected results could still be achieved without their involvement [24]. However, such free rider explanation seems to be illogical as the mean score of group efficacy was not too high. Thus, the second reason might be that some people did not fully believe in joint efforts but participated in collective action as they were controlled by the social norms of Vietnamese villages' collectivist culture [25,26]. This possibility can be partly supported by citizens' lack of confidence in local authorities' management of land and environment [3,20,28]. In addition, the social value of maintaining group cohesion might force some people to participate in their neighbors' collective action regardless of their perception of its ineffectiveness. If that was the case, there would be an interesting difference between Vietnam and some of Asian countries in the impacts of collectivism on collective action. Specifically, the appreciation of group harmony inhibits the desire to participate in collective action among people from Japan, the Philippines, Indonesia, Korea, and Taiwan [13 -16]. Meanwhile, this social value encourages Vietnamese people to take collective action. This distinction may stem from the fact that the collective action relating to land confiscation and environmental pollution in Vietnam is by nature the conflict between a group of people and their local authorities rather than other groups of people [1 -4]. It is possible that in Vietnam, collective action against people from the same village or commune is also considered a violation of cultural value. Further research which examines individuals' perception of their potential personal influence on the success of collective action [i.e., participative efficacy] [28], the social pressure put on them if they disengage in collective action, and specific forms of conflicts [e.g., between groups of people or between people and the government], is needed to verify these arguments.

The Mediators of the Relationship between Politicized Identity and Collective Action
Inconsistent with our prediction and many previous findings [10], the politicized identity was not found as the predictor of the group efficacy. Similar results were also found in the study of van Zomeren,Postmes,and Spear [11]. The researchers argued that a politicized group that included diverse goals and action directions might make it difficult for the members to evaluate its effectiveness. These authors' explanations may be relevant to our research findings. In the present study, there might be some people who identified with the politicized group , which intended to block garbage trucks, but did not choose to follow this way of protest, In other words, there might be a normative discrepancy between participants' moral beliefs and the content of politicized identity [13]. It is necessary to mention two cultural features of the Vietnamese people to irradicate this notion: Vietnamese people often value affection over reason and their villages are characterized by strong community cohesion [25,26]. Thus, when confronted with moral judgments, although Vietnamese people may disagree with each other regarding certain behaviors, they tend to sympathize with each other, especially among people living in the same village or having the same background. In this case, it was likely that some participants sympathized with the people blocking the garbage trucks, yet disagreed about this form of collective action, leading to the results showing that identification did not influence group efficacy directly. Another possible cause for the null relationships between politicized identity and group efficacy is that given results of previous protests, participants might not believe that blocking the garbage trucks could change a protracted problem. This explanation, to some extent, resonates with that of several prior studies [14,17,29]. Those studies argued that as members of the low-status group had little hope and scope for change they gave up the idea of participating in collective action regardless of their level of group identification and perceived injustice. This pattern of behavior suggests that these people distrust the effectiveness of methods or directions of collective protest suggested by any politicized group, resulting in a nonsignificant relation between group identification and group efficacy. Further research is needed to examine these hypotheses.
In addition, as we expected, regression results suggested that group-based anger was able to partially explain the relationship between politicized identity and collective action. This finding is consistent with several previous studies as well as the idea that group identity is the basis for individuals to experience group-based relative deprivation [10]. Considering both emotional i.e., group-based anger and instrumental i.e., group efficacy pathways through which social identity influences collective action, our results suggested that for Vietnamese people who are facing unfairness in land or environmental issues, collective action is more likely a way to release their negative feelings e.g., anger rather than to achieve social changes. This tendency, as mentioned above, may stem from people's disappointment about their local authorities. With no hope for change and the negative impacts of injustice, it is easier for people to take collective action as a way to express their anger.

The Mediators of the Relationship between Moral Conviction and Collective Action
According to regression and path analyses, group-based anger was found to be predicted by moral conviction and also the mediator partialy explaining the relationship between moral conviction and collective action. These findings were consistent with our expectations and previous studies on Western samples [11], proposing a universal pathway between moral beliefs and collective action via group-based anger. In addition, consistent with our prediction and several previous studies, moral conviction had a direct impact on politicized identity through which it influenced on collective action. However, it should be noted that the relationship between moral conviction and politicized group identification might not imply participants' agreement with blocking garbage trucks. Instead, as indicated above, this positive relationship might be merely a manifestation of mutual sympathy among residents of NBH communes who suffered from the same situation of injustice. Besides, although moral conviction had a direct effect on group efficacy, there was no indirect effect of moral conviction on collective action through group efficacy. As the SIMCA argued, when individuals' moral conviction is violated their confidence in the effectiveness of the group will be strengthened as they strongly believe that there are many other people will have the same moral stance with them [11]. However, as discussed, stronger group efficacy did not guarantee that people would participate in collective action.
Based on the fact that the relationship between moral conviction and collective action was not fully mediated by the remaining variables in the SIMCA, we added one more hypothetical direct impact path from moral conviction to collective action in the path model. The analysis results confirmed the hypothesis, suggesting that there were other unexplored mediators. The direct impact of moral conviction on collective action, along with the fact that group-efficacy was not predicted by politicized identity with the contents of blocking garbage trucks and did not affect collective action, raises questions about the normative fit between moral beliefs and politicized identity contents. Blocking garbage trucks for some people might not be an action in accordance with their moral beliefs. Therefore, though they could empathize with the group of people blocking garbage trucks, they do not agree with and follow that group's agenda. Instead, these people may actually both emotionally and rationally identify with other politicized groups with different action orientations that are more in line with their moral beliefs. Future research on the specific types of collective struggles that Vietnamese people tend to employ will help clarify this outcome.

CONCLUSION
Our research findings have provided preliminary evidence for supporting and challenging the applicability of the SIMCA in predicting collective action in the Vietnamese context. The positive relationships of group-based anger, politicized identity, and moral convictions with collective action were confirmed, suggesting a similar pattern with Western countries in mobilizing collective action. Intriguingly, Vietnamese participants did not show any pattern in these relationships as found in other samples from China, the Philippines, or Indonesia. The null relationships of group efficacy with politicized identity and collective action demonstrated the role of Vietnam's unique cultural and political characteristics in shaping people's collective action. Overall, the findings seem to favor only part of the SIMCA. However, we believe that the results indicate the SIMCA's potential to point out the psychological mechanisms that motivate Vietnamese people to participate in collective action. It should be noted that, in addition to the politicized identity with the contents of blocking garbage trucks used in this study, there are still other politicized identities with diverse contents. We believe that studies specifying politicized identities and examining people's identification with each of them in light of their normative fit with people's moral beliefs could further clarify Vietnamese people's distinction between affection and reason in making decisions on collective action.
This study also has certain limitations affecting the results. Firstly, the sample was convenient and small. Therefore, there was a lack of representativeness of the sample and it was difficult to generalize the results. Moreover, as the present study was on a topic deemed as a sensitive political one in Vietnam, its voluntary participants might have certain biases. Future research needs to overcome this limitation by collecting data from larger random samples. Second, it was unclear whether items on the scale of politicized identity were capable of distinguishing between empathy and identification while these two psychological processes for the Vietnamese people could overlap. This raises the need to develop a valid measure that distinguishes empathy from identification to apply in the context of Vietnam. Third, this study did not investigate the variables that demonstrate the normative fit between moral beliefs and identity contents, and between particular politicized identities and collective action. As a result, although this study might partly explain why people blocked garbage trucks but had difficulties in identifying and explaining any other forms of collective action that people could take. Studies that build up a list of possible politicized identities and specific forms of collective action can provide a more complete picture of people's engagement in collective action as well as enhance the SIMCA's predictability of collective action.
In summary, the present study demonstrated that the SIMCA is appropriate for the Vietnamese context in explaining collective action related to land and environmental disputes. Theoretically, this study not only clarifies the applicability of the SIMCA in a culture with collective characteristics but also points out the cultural aspect that can affect the relationship between the variables of the SIMCA. From a practical perspective, these findings are the basis for proposing a new perspective on collective action for government agencies and officials as well as social activists They also call for attention to reasonable psychological processes that have led to collective action and the construction of more legal mechanisms for the people to protest and complaint.

ETHICS APPROVAL AND CONSENT TO PARTI-CIPATE
This study was approved by The Institute of Policy and Management's Institutional Review Board (15/KHDT-IPAM).

HUMAN AND ANIMAL RIGHTS
Not applicable.

CONSENT FOR PUBLICATION
Informed consent was taken from all the participants when they were enrolled.

AVAILABILITY OF DATA AND MATERIALS
Not applicable.