text in 
English (pdf)
Article in xml format
Article references
Automatic translation
Send this article by e-mail
Cited by SciELO 
Cited by Google 
Similars in
SciELO 
Similars in Google 
Permalink
Identity fusion: a systematic review
The theory of identity fusion has completed a decade since the first article introducing it to the field of psychology was published (Swann, Gómez, Seyle, Morales, & Huici, 2009). This theory was born with the intention of explaining a particular phenomenon: why are some people capable of making extreme sacrifices, to the point of giving their lives for their group? The authors propose that this disposition to extreme sacrifice would be motivated by a highly salient personal and group identity between individuals, with a visceral feeling of deep union between the personal self and the social self, so that the delimitation between both identities becomes indistinguishable (e.g., Gómez & Vázquez, 2015; Swann, Jetten, Gómez, Whitehouse, & Bastian 2012).
As a construct, identity fusion is associated with relational ties (i.e., feelings toward individual group members) and collective ties (i.e., feelings toward the group as a whole; e.g., Gómez et al., 2019; Gómez, Brooks et al., 2011), which create the perception of connection and reciprocal strength between personal identity and group identity (Besta, 2018; Gómez, Brooks et al., 2011) . Because of this strong unity with the group, the merged individuals represent the other group members as if they were their own relatives (Robert, Virpi, & John, 2019; Swann, Buhrmester et al., 2014; Whitehouse et al., 2014), motivating them to perform extreme behaviors in favor of the group (e.g., Buhrmester & Swann, 2015; Fredman et al., 2015; Swann & Buhrmester, 2015).
Identity fusion has been founded on four fundamental principles that conceptually capture its nature. Multiple investigations have demonstrated consistent evidence of these principles, supporting the theoretical basis of identity fusion (e.g., Besta, Mattingly, & Blazek, 2015; Gómez, Morales, Hart, Vázquez, & Swann, 2011; Heger & Gaertner, 2018; Vázquez, Gómez, & Swann, 2017): the personal agent self, identity synergy, relational ties, and irrevocability (Gómez & Vázquez, 2015; Swann et al., 2012).
The principle of the personal agent self suggests that the merged person maintains intentional actions that benefit the group (Fredman et al., 2015). These actions are outstanding even in group contexts, where the personal self is activated along with the social self (Swann, Gomez, Huici, Morales, & Hixon, 2010). In this way, the merged person feels capable of performing behaviours that in his or her opinion will have consequences for the whole group (Gómez & Vázquez, 2015).
The principle of identity synergy refers to the synchrony that develops the personal self with the social self forming a reciprocal combination between both identities (Gómez, Brooks et al., 2011; Swann et al., 2009), which causes that when one is activated, the other is also activated, amplifying the behavior of the merged person (Heger & Gaertner, 2018; Swann et al., 2012).
The principle of relational ties refers to the fact that the merged subjects recognize the members of the group both by their personal identities and by their social identities (Swann, Gómez, Dovidio, Hart, & Jetten, 2010). The combination of both identities through this type of recognition develops in the merged individuals a strong bond with the group members (e.g., Besta, 2014; Gómez, Brooks et al., 2011).
Finally, the principle of irreversibility refers to the fact that merged persons tend to remain merged over time (Vázquez et al., 2017; Swann et al., 2012; Swann et al., 2015). This is because fused people build the relational and collective ties that bind them emotionally intensely to the group (Gómez et al., 2019), thus reinforcing the sense of their social and personal selves (Gómez, Morales et al., 2011).
While there have been some theoretical studies that account for the fundamental properties of identity fusion theory (e.g., Buhrmester & Swann, 2015; Fredman et al, 2012; Swann & Buhrmester, 2015; Whitehouse & Lanman, 2014; Yuan, Tao, & Lu, 2014), to date no article has conducted a review that systematically synthesizes and groups all the empirical studies that have involved identity fusion. Therefore, the objective of the present theoretical study (Montero & Leon, 2007), is to perform a systematic review of the empirical studies (Ato, Lopez, & Benavente, 2013) that have reported the use of the identity fusion construct between the years 2009 to 2018.
Method
Procedure and search strategies
A systematic review of the literature was conducted following the guidelines and recommendations of the PRISMA statement, complying with items 1, 2, 3, 6, 7, 8, 9, 10, 11, 14, 17, 18, 23, 24, 25, 26 and 28 of its checklist (Liberati et al., 2009; Urrútia & Bonfill, 2010). The search for articles published between 2009 and 2018 was configured by consulting seven databases (n = 351; Web of Science = 87, Scopus = 55, ProQuest = 65, ScienceDirect = 46, Willey Online Library = 35, EBSCO = 38 and JSTORE = 25). Article research was limited to studies conducted in English and Spanish using the keywords "identity fusion" and "fusión de identidad". The search was limited to the following areas of research: social psychology; social identity; identity; behavior; group dynamics; psychology; group identity; social sciences; social behavior. Only articles with empirical data were included, discarding theoretical and instrumental works on identity fusion.
Selection of studies
The studies were selected in stages (see Figure 1). First, all the articles collected in the databases mentioned above were compiled (n = 351). Second, the titles were read and all duplicate articles were removed (n = 142). Third, the titles, abstracts, keywords and instruments used were read, eliminating articles that did not meet the inclusion criteria (n = 129). Finally, a full-text reading was carried out by eliminating articles on theoretical, instrumental or non-centric studies on identity fusion (n = 28).
Summary of results
Once the selection was completed (n = 52), the results were synthesized in order to compare the different studies. This procedure was carried out by extracting the following data: 1) author(s), 2) year of publication, 3) sample(s), 4) research design, 5) fusion measuring instrument(s), 6) reference group(s), 7) variables/manipulations included in the studies and 8) main results.
Table 1 Synthesis of empirical studies addressing the theory of identity fusion
Note: CO = Correlational; DE = Descriptive; EX = Experimental; MP = Pictorial Measure; MV = Verbal Measure; IG = Group Identification; DIS = Willingness to fight and die for the group; HaM = male-to-female; MaH = male-to-female. The percentage in the reference group column refers to the percentage of participants fused with the group.
Results
The main results of each study are described in Table 1. Within the 52 articles included in the synthesis, 117 empirical studies covering identity fusion were detected as part of their results. Regarding the research designs, of the 117 studies, 69 (59%) were correlational, 45 (38.5%) experimental, 2 (1.7%) exploratory and 1 (0.9%) descriptive. In terms of the origin of the participants, more than 23 countries were identified, the main ones being Spain with 38% (n = 49), the United States with 20.2% (n = 26), Poland with 18.6% (n = 24) and other countries (e.g., Germany, Australia, Brazil, Chile, China, England, India, Indonesia, Israel, Japan, Lebanon, Libya, Morocco, New Zealand, Norway, Singapore, South Africa, South Korea) with 23.3% (n = 30).
As for the participants, 45% (n = 58) were university students, 38.8% (n = 50) general population and 16.3% (n = 21) other types of population (e.g., activists, soccer fans, twins, couples, guerrillas, military, transsexuals, children and adolescents).
Regarding fusion measurement instruments, 34.2% (n = 41) of the studies used the pictorial measure of identity fusion (Swann et al., 2009), 63.3% (n = 76) the verbal measure of identity fusion (Gómez, Brooks et al., 2011) and 2.5% (n = 3) the dynamic index of identity fusion (DIFI, Jiménez et al., 2016).
Regarding reference groups or targets, 64.1% (n = 75) of the studies used the country as a reference group, 14.5% (n = 17) family and friends, 29.1% (n = 34) specific groups (e.g., political parties, guerrillas, military, sports 0roups, online 0roups, educational institutions, intentional communities, cities of residence) and 10.3 (n = 12) other reference targets (e.g., candidates, trademarks, public figures).
Regarding the variables that have been most studied along with identity fusion, those related to identity (n = 64; 54.7%), motivation to sacrifice (n = 60; 51.3%), relationship with the group (n = 41; 35.3%), individual psychological variables (n = 30; 25.6%), bonds (n = 24; 20.5%) and other variables (n = 41; 35.3%) have been studied. While the least studied variables along with identity fusion have been feelings and emotions (n = 20; 17.1%), personal agency (n = 14; 12%), well-being (n = 7; 6%) and affections (n = 5; 4.3%). The grouping of the variables studied in relation to identity fusion can be seen in Table 2.
Table 2 Grouping of variables studied in relation to identity fusion Cate0ories Variables
Note: Some variables may belong to more than one category.
Finally, the main results of the articles analyzed indicate that identity fusion is a strong predictor of extreme sacrificial behaviors by the group (e.g., Besta et al., 2013; Gomez, Morales et al., 2011; Heger & Gaertner, 2018; Kunst et al., 2018; Paredes et al., 2018; Sheikh et al., 2016; Swann et al, 2009; Swann et al., 2010; Swann, Buhrmester et al, 2014; Swann, Gómez et al, 2014; Vázquez, Gómez, & Swann, 2017) and behaviours that involve giving (e.g., Gómez, Morales et al, 2011; Segal et al, 2018; Semnani-Azad et al, 2012) and asking for help from the group (e.g., Reddish et al, 2016; Semnani-Azad et al, 2012). In commercial contexts, identity fusion has been successful in predictin0 consumer preferences for domestic products (Yoo et al., 2014), and consumers fused with their brands were predisposed to follow their relationship with their marks despite being aware of some of their ethical transgressions (Lin & Sung, 2014).
Also, identity fusion has been mainly related to extreme culling behaviors by the group (e.g., Besta, 2014; Besta et al., 2014; Besta, Mattingly et al., 2015; Besta, Szulc et al., 2015; Buhrmester et al., 2015; Carnes & Lickel, 2018; Fredman et al., 2017; Kossakowski & Besta, 2018; Newson et al, 2018; Sheikh et al, 2016; Swann et al, 2009; Swann et al, 2015; Swann, Buhrmester et al, 2014; Swann, Gomez, Dovidio et al, 2010; Swann, Gomez, Huici et al, 2010; Vazquez et al, 2015; Vazquez et al, 2017) or by individuals (Joo & Park, 2017; Vazquez, Gomez, Ordoñana et al, 2017; Walsh & Neff, 2018). In addition, in numerous studies identity fusion has been related to 0roup identity (e.g., Besta et al., 2014; Besta, Mattingly et al., 2015; Besta, Szulc et al., 2015; Buhrmester et al., 2012; Swann et al., 2009; Swann, Gómez, Huici et al., 2010), group support and commitment (e.g., Besta & Kossakowski, 2018; Besta et al, 2018; Besta, 2018; Buhrmester et al., 2015; Buhrmester, Newson et al., 2018; Carnes & Lickel, 2018; Dahling & Gutworth, 2017; Howard & Magee, 2013; Misch et al, 2018; Sheikh et al., 2014; Swann, Gomez et al., 2014; Vazquez, Gomez, & Swann, 2017; Zumeta, Basabe et al., 2016), perceived social support (e.g., Grinde et al, 2018; Howard & Magee, 2013), loyalty (Newson et al., 2016) even under conditions of ostracism (Gómez, Morales et al., 2011), feelings, affections and emotions towards the group (Buhrmester, Burnham et al, 2018; Carnes & Lickel, 2018; Dahling & Gutworth, 2017; Grinde et al., 2018; Howard & Magee, 2013; Jong et al., 2015; Joo & Park, 2017; Paez et al, 2015; Segal et al., 2018; Swann, Gomez et al., 2014; Zumeta, Basabe et al., 2016; Zumeta, Oriol et al., 2016) and values: morals (Kunst et al., 2018; Sheikh et al, 2014; Swann, Gomez et al., 2014), sacred (Carnes & Lickel, 2018; Sheikh et al., 2016), democratic (Sheikh et al., 2016), and cultural (Kossakowski & Besta, 2018).
Other studies have shown that identity fusion is related to the perception of kinship (Buhrmester et al., 2015), quality of life (e.g., Buhrmester et al., 2012; Jaskiewicz & Besta, 2014) , life satisfaction (Grinde et al., 2018), perception of a leader's charisma (Steffens et al, 2017; van Dick et al., 2018), religiousness (Besta et al., 2014; Fredman et al., 2017; Sheikh et al., 2014), nationalism (Besta, 2014), political extremism (Besta, Szulc et al., 2015), political orientation (Kunst et al., 2018) and support for group irregularities (Besta et al., 2014).
On the other hand, the mediation models within the studies analyzed, have shown that the fusion of identity mediates the relationship between: the accessibility of the neighborhood and the quality of life in the neighborhood (Jaskiewicz & Besta, 2014), moral convictions and the disposition to extreme sacrifice behaviors (Carnes & Lickel, 2018), the memory of a traumatic event and pro-social behavior (Segal et al, 2018), self-conformation and loyalty to the group (Newson et al., 2016), and, the death of a leader and the perception of his or her charisma (Steffens et al., 2017). Likewise, in three studies, the fusion of identity with the twin measured the effect that zygosity had on the desire for contact and the experience with the twin (Vázquez, Gómez, Ordoñana et al., 2017). Finally, fusion with a recently dead iconic (or famous) animal mediated the relationship between the state of dysphoria and fusion with an animalist organization (Buhrmester, Burnham et al., 2018).
In other models of mediation that have involved identity fusion, it has been identified that: personal agency mediates the relationship between identity fusion (in the condition of excitement) and the action of donating money to the group (Swann, Gomez, Huici et al, 2010); both personal a0ency and invulnerability mediate the relationship between identity fusion and the willingness to fight and die for the group (Gómez, Brooks et al., 2011); emotional engagement mediates the relationship between identity fusion and extreme sacrifice (Swann, Gómez et al., 2014); clarity of self-concept mediates the relationship between identity fusion and personal agency (Besta, Mattingly et al, 2015) ; right-wing and left-wing authoritarianism mediates the relationship between identity fusion and the inclination towards violence for the change of the social system (Besta, Szulc et al., 2015); right-wing authoritarianism mediates the relationship between identity fusion and the willingness to fight and die for the country (Besta, Szulc et al, 2015); the psychological kinship, mediates the effect of the identity fusion on the support actions, the empathic preoccupation and the self-sacrifice (Buhrmester et al., 2015); the time of reflection on negative events, mediates the relation between a shared negative experience and the identity fusion (Jong et al, 2015); emotional synchrony, mediates the relationship between the level of collective participation and identity fusion (Páez et al., 2015); emotional synchrony, mediates the relationship between identity fusion and collective effectiveness (Zumeta, Oriol et al., 2016); the experience of shared flow, mediates the relationship between the level of involvement in a collective activity and identity fusion (Zumeta, Basabe et al, 2016); collective, but not relational, bonds mediate the identity fusion before and after three historical events negative for the stability of the group (Vázquez, Gómez, & Swann, 2017); the identity fusion (with an external group), mediates the relation between the political orientation of the left and the extreme protest (Kunst et al, 2018); self-expansion and self-efficacy mediate the relationship between identity fusion and collective action (Besta et al., 2018); self-expansion and group self-efficacy mediate the relationship between identity fusion and collective action (Besta & Kossakowski, 2018); leadership identity and identity fusion mediate the relationship between the death of a leader and the perception of his or her charisma (van Dick et al., 2018).
With regard to models of moderation that have included identity fusion, it has been noted that: the status of a group evaluator moderates the relationship between identity fusion and radical support for the group (Besta et al., 2013); values moderate the relationship between identity fusion and making costly sacrifices (Sheikh et al., 2014); negative affects moderate the relationship between memory of a negative experience and identity fusion (Jong et al., 2015); impulsivity moderates the relationship between identity fusion (with partner) and self-sacrifice by partner (Joo & Park, 2017); independent self-moderates the relationship between interdependent self and identity fusion (Besta, 2018); self-verification moderates the relationship between group verification and identity fusion (Besta, 2018); self-description as an agent moderates the relationship between self-description as a community being and identity fusion (Besta, 2018); and, police perception and acceptance of the system moderates the relationship between identity fusion and collective action (Besta & Kossakowski, 2018).
Finally, in the models of moderate mediation within the articles analyzed, it has been found that: shared values moderate the effect of identity fusion on family ties, while family ties mediate the relationship between identity fusion and support of extreme actions by the group (Swann, Buhrmester et al, 2014); trust in the sacrifice of other fused individuals mediates the relationship between identity fusion and the willingness to fight and die for the group, while justification of sacrifice moderates the effect of trust in the sacrifice of other fused individuals and identity fusion on the willingness to fight and die for the group (Paredes et al, 2018); finally, fear and personal harm caused by a natural disaster moderates the effect of memory (of the natural disaster) on identity fusion, while identity fusion mediates the relationship between memory of the natural disaster and prosocial behavior (Segal et al., 2018).
Discussion
The purpose of this paper was to review and synthesize empirical studies using the theory of identity fusion between 2009 and 2018.
The main results of the articles analyzed indicate that identity fusion is a strong predictor of extreme group-slaughter behaviors. Fused people would be highly oriented to group support and commitment, creating strong relational ties through feelings, affections and emotions towards the group, involving moral values, considered sacred and unrenounceable. This dynamic causes the fused people to feel that the members of their group, are an extension of their own family to which they must protect with determination. Classical theories, by not considering the relevance of relational ties within their constructs, fail to generate models that can predict behaviors of extreme sacrifice by the group, as if it does the theory of identity fusion (Gomez et al., 2019).
The present review demonstrates that the systematic development of evidence supporting the theory of identity fusion is continuously progressing, being applied to diverse populations (e.g., hooligans, football fans, terrorists, combatants, siblings, romantic couples, fighters, military, activists, couples, guerrillas, transsexuals, children and adolescents), reaching countries on five continents (e.g., Spain, United States, Poland, Germany, Australia, Brazil, Chile, China, South Korea, India, Indonesia, England, Northern Ireland, Israel, Japan, Lebanon, Libya, Morocco, Norway, New Zealand, Singapore, South Africa), targeting various reference groups (e.g., countries, families, friends, political parties, combat squads, sports groups, online groups, educational institutions, intentional communities, cities of residence, candidates, trademarks, public figures) and predicting extreme sacrifice even through measurements of actual behavior (e.g., donations, sex change, video game performance, answers to tram dilemmas).
Although all the evidence presented is very valuable, it does have some limitations. Most participants in identity fusion studies are Spanish, American and Polish, half of them university students, i.e., WEIRD population, who are characterized as belonging to Western, educated, industrialized, rich and democratic countries (Henrich, Heine, & Norenzayan, 2010). This is a common problem in psychology research, so it is necessary to continue investigating the behavior of identity fusion theory in other socio-cultural contexts (Henrich et al., 2010).
A second limitation is that much of the evidence relating to identity fusion and extreme sacrifice for the group is based on the scale of willingness to fight and die used by Swann et al. (2009). In this regard, it would be desirable to continue to provide evidence of the predictive power of identity fusion using different scales (e.g., scale of self-sacrifice: Bélanger, Caouette, Sharvit, & Dugas, 2014) or situations that measure extreme sacrifice for the group (e.g., implicit measure "The Boom Task": Bélanger et al., 2014; Bélanger, Schumpe, Menon, Ng, & Nociti, 2018).
Most studies use the country of origin as the reference group, implicitly implying that there would be no substantial difference between the country as a nation-state (e.g., Spain) or as a people (e.g., Spaniards). In this sense, it would be necessary to state under pressure which is the reference group used in each study, since in different cultural contexts the level of identity fusion with the nation-state could be different from the level of fusion with the people.
Finally, it seems that the theory of identity fusion could have different guidelines that need to be further explored (e.g., interpersonal fusion, protofusion, fusion with organizational groups), and others that have not even been explored (e.g., in migration contexts: fusion with the country of origin/host). This leaves multiple lines of research to be developed and a long way to go.
