The Influence of Sustainable Positioning on eWOM and Brand Loyalty: Analysis of Credible Sources and Transparency Practices Based on the S-O-R Model

With increased concern for environmental and social issues, consumers and the apparel industry have become more interested in the topic of sustainability. Numerous brands strive to reposition in sustainability by employing credible sources and maintaining information transparency to get consumers’ recognition. By employing the stimulus-organism-response (S-O-R) framework, this study experimented with how sustainability positioning with credible sources (EPA vs. Celebrity vs. Social Media Influencer) and high (vs. low) transparency influence brand attachment, trust, and identification, leading to eWOM and brand loyalty. The findings indicate that sustainable positioning with credible sources (i.e., EPA and Social Media influencers) could achieve consumers’ positive brand attachment, trust, and identification in social media marketing. However, we did not find evidence of the impact of high (vs. low) transparency on these dependable variables. Furthermore, brand loyalty and eWOM are significantly influenced by consumers’ brand attachment and trust, whereas brand identification positively affects brand loyalty only, not eWOM. Additionally, this study found that women and higher-income groups had a high preference for sustainable brands.


Introduction
Global apparel and footwear retail had total revenue of 1.9 trillion dollars in 2019, and the United States is the largest apparel market in the world, consisting of approximately USD 368 billion in 2019 [1]. The apparel business in the United States is constantly evolving and is becoming more challenging due to emerging customer preferences and requirements. Thus, apparel brands must be concentrated on the target market's buying trends and rapid shifts in consumer habits. Gen Zers, born between 1997 and 2012 [2][3][4], is a vital market segment for retailers, with purchasing capacity as high as $143 billion in 2017 [5]. Gen Zers are the most influential customer group in the United States, with almost 90.5 million members [6]. Nearly nine out of ten Gen Zers (87%) are concerned about the environment and the world's future [7], and 57% of them want environmentally friendly goods [8]. Besides, two-thirds of global shoppers claim that they will not purchase or boycott products depending on business organizations' positions on contentious environmental topics [9]. As a result, apparel brands are promoting their sustainable practices to affect consumers buying intentions and behavior. To accelerate the promotion and communication about sustainability issues, marketers are utilizing social media as an effective advertising tactic [10].
Numerous research in the retail and service industries have used the S-O-R model to successfully employ environmental stimuli as indicators of emotional responses and consumer behaviors [11][12][13]. Moreover, many studies on sustainability in retailing have been conducted; including supply chains for fashion products [14,15], sustainable goods assortment and marketing [16,17], building sustainable brand identity [18,19], and environmental consumption preference [20,21]. However, few research findings compare the relative value of sustainability as a factor for apparel purchases [22]. Moreover, some researchers suggested that to convey the message of sustainable practices; transparency can play an important role [23][24][25][26]. Still, there is a lack of studies focused on the transparency of sustainable disclosures in the apparel industry [25]. Additionally, research examining the transparency of sustainability practices is scarce in the context of social media marketing. Earlier studies found that credible sources can be beneficial in communicating the message of sustainability in product marketing, consumers' product evaluations, and purchase-related decisions [27,28]. However, in this era of social media, Gen Zers' mostly followed credible sources like social media influencers, and celebrities were not examined on sustainable message promotion. Thus, there is a void for research in this area.
Therefore, this study explored US Gen Zers' preference towards sustainable brands based on endorsements by trusted sources, such as government agencies, social influencers, and celebrities. This study examined the impact of sustainable positioning with different credible sources and transparency practices on Gen Zer's brand attitudes (i.e., attachment, trust, identification), which can lead to electronic word-of-mouth (eWOM), and brand loyalty.

Theoretical Framework: S-O-R Model
In psychology, consumer behavior, and marketing research, the stimulus-organism response (S-O-R) model has been commonly used [29][30][31][32]. Mehrabian and Russell [33] suggested the form of the S-O-R (stimulus-organism-response) model that depicts the occurrence of a person's exposure to environmental stimuli. Bagozzi [34] mentioned the inputs are exterior to the individual and include mixed positioning variable quantity and other ecological information. Given the importance of environmental cues in shaping customer behavior, the S-O-R model offers a systematic way to investigate the impact of ecological factors on consumers' cognitive or emotional reactions and, therefore, their intention to engage in organic buying activity [35]. Chang and Jai [36] investigated the fast-fashion brand's sustainability positioning techniques as a stimulus and perceived corporate social responsibility (CSR) effort as an organism and found that they can influence purchase intentions significantly. Recently, a fiery challenge for apparel brands is that consumers may perceive sustainability disclosure efforts as greenwashing. By utilizing the S-O-R framework, several studies found credible sources and transparency had a positive impact on consumers' attachment and trust [37][38][39][40][41]. However, to the best of our knowledge, applying the S-O-R model, previous studies did not experiment with sustainable positioning based on different credible sources (such as social media influencers) and transparency as stimuli in dealing with consumers' greenwashing perception. Thus, applying the S-O-R model, this study investigated the effect of sustainable positioning (i.e., credible sources and transparency) as the stimulus on eWOM and customer loyalty as the external responses through the mediating factors (i.e., brand attachment, trust, and identification) as the internal organism ( Figure 1).
With increasing environmental concerns, customers' desire to understand the impact of the supply chain increases. Nowadays, consumers demand goods with a low ecological effect while still having a positive social impact such as fair wages, a safe working environment, saving water/energy, reducing carbon footprints, reducing waste, etc. [42]. To relate to these environmentally aware customers, companies distinguish themselves from their rivals by positioning themselves as sustainable [36,43,44]. For example, Everlane disclosed its ethical and sustainable supply chain, environmentally friendly materials, production, and shipment cost on its website and called it radical transparency. The success of sustainable positioning methods has been addressed in the literature [36,[44][45][46][47].

Sustainable Brand Positioning using Credible Sources and Transparency
With increasing environmental concerns, customers' desire to understand the impact of the supply chain increases. Nowadays, consumers demand goods with a low ecological effect while still having a positive social impact such as fair wages, a safe working environment, saving water/energy, reducing carbon footprints, reducing waste, etc. [42]. To relate to these environmentally aware customers, companies distinguish themselves from their rivals by positioning themselves as sustainable [36,43,44]. For example, Everlane disclosed its ethical and sustainable supply chain, environmentally friendly materials, production, and shipment cost on its website and called it radical transparency. The success of sustainable positioning methods has been addressed in the literature [36,[44][45][46][47].
However, consumers may perceive sustainable signals as fake promises, deceptive sustainability ads, and greenwashing [48][49][50]. Thus, the sustainable brand might not be able to persuade buyers of the environmental benefits [50][51][52]. This challenge can be solved by displaying support from credible sources such as third-party environmental groups and making substantive statements in practices [53]. Previous studies found that the Environmental Protection Agency (EPA) seal is deemed to be trustworthy among both the general population and environmentally conscious consumers as it is affiliated with a government agency and may assist in guaranteeing that the retailer's disclosed information is valid and trustworthy [27,28]. Thus, this research experimented with the impact of sustainable positioning with a seal of the EPA as a credible source in enhancing brand attachment, trust, and identification which leads to eWOM, and customers' loyalty.
These days, younger generations have been very active in social media. Therefore, social influencers and public figures established themselves as possible endorsers and credible sources to their followers. Many studies used social media influencers and celebrities as credible sources to examine marketing effectiveness, raise product awareness and make apparel purchasing decisions [54][55][56][57]. However, there was a void in the literature on promoting sustainable positioning by social media influencers and celebrities as credible sources. Kay et al. [58] found that micro-social influencers have greater acceptability and impact on consumers' purchase intention than macroinfluencers. Thus, this study investigated the effect of US Gen Zer's most acceptable credible sources, such as social influencers and public figures/celebrities, on endorsing sustainable brands.
A study by Lin et al. [59] found that transparency is a crucial driver of sustainability perceived value, which can drive brand loyalty. In the apparel sector, transparency means openly sharing information about how, where, and by whom a product was made [60]. An environmentally concerned consumer expects full transparency across the retail chain

Sustainable Brand Positioning using Credible Sources and Transparency
However, consumers may perceive sustainable signals as fake promises, deceptive sustainability ads, and greenwashing [48][49][50]. Thus, the sustainable brand might not be able to persuade buyers of the environmental benefits [50][51][52]. This challenge can be solved by displaying support from credible sources such as third-party environmental groups and making substantive statements in practices [53]. Previous studies found that the Environmental Protection Agency (EPA) seal is deemed to be trustworthy among both the general population and environmentally conscious consumers as it is affiliated with a government agency and may assist in guaranteeing that the retailer's disclosed information is valid and trustworthy [27,28]. Thus, this research experimented with the impact of sustainable positioning with a seal of the EPA as a credible source in enhancing brand attachment, trust, and identification which leads to eWOM, and customers' loyalty.
These days, younger generations have been very active in social media. Therefore, social influencers and public figures established themselves as possible endorsers and credible sources to their followers. Many studies used social media influencers and celebrities as credible sources to examine marketing effectiveness, raise product awareness and make apparel purchasing decisions [54][55][56][57]. However, there was a void in the literature on promoting sustainable positioning by social media influencers and celebrities as credible sources. Kay et al. [58] found that micro-social influencers have greater acceptability and impact on consumers' purchase intention than macro-influencers. Thus, this study investigated the effect of US Gen Zer's most acceptable credible sources, such as social influencers and public figures/celebrities, on endorsing sustainable brands.
A study by Lin et al. [59] found that transparency is a crucial driver of sustainability perceived value, which can drive brand loyalty. In the apparel sector, transparency means openly sharing information about how, where, and by whom a product was made [60]. An environmentally concerned consumer expects full transparency across the retail chain and is willing to know where and how products are fabricated to the design provenance and quality [9]. Studies also found that compared to low transparency, consumers exposed to promotions with highly transparent information had more positive attitudes toward sustainable product claims [61,62]. Moreover, a high level of perceived transparency on sustainability can help a brand to achieve customers' appreciation of socially responsible efforts and avoid greenwashing charges [63,64]. Studies also found that the impact of eWOM depends on source credibility and information transparency [65][66][67]. With this view, this study explored the effect of credible sources and transparency on eWOM and brand loyalty through brand attachment, trust, and identification.

Brand Attachment
Brand attachment can be defined as the intense emotion customers can receive from a long-term relationship with brands, comparable to the feelings experienced in close friendship relationships [68]. It is crucial for businesses because it will help them mitigate customer defections and achieve forgiveness when faced with negative facts [69]. Several studies found that sustainability practices can significantly predict brand attachment and lead to eWOM and brand loyalty [70,71]. Thus, this study investigated the impacts of sustainable credible sources and transparency on brand attachment. The following hypotheses were developed: Hypothesis 1a (H1a): Consumers exposed to sustainable brand positioning with credible sources will have a higher degree of brand attachment than those exposed to no credible sources.
Hypothesis 1b (H1b): Consumers exposed to sustainable brand positioning with high transparency will have a higher degree of brand attachment than those exposed to low transparency.

Brand Trust
Brand trust is generally described as the willingness to depend on the brand [72]. Chaudhuri and Holbrook [73] depicted brand trust as consumers' propensity to rely on a brand's ability to fulfill its claimed role. It is a primarily cognitive element that has emotional and conative contents, unlike confidence (a feeling of assurance) and reliance [74]. In customer purchasing contexts, the importance of trust in establishing and retaining brand loyalty has been thoroughly researched [73,75]. Moreover, it is closely linked to customers' perceptions of sustainable fashion products, leading to eWOM and brand loyalty [76,77]. Therefore, this study looked at the impact of sustainable positioning with various credible sources and transparency practices on brand trust with the following hypotheses: Hypothesis 2a (H2a): Consumers exposed to sustainable brand positioning with credible sources will have a higher degree of brand trust than those exposed to no credible sources.
Hypothesis 2b (H2b): Consumers exposed to sustainable brand positioning with high transparency will have a higher degree of brand trust than those exposed to low transparency.

Brand Identification
Brand identification is the degree to which the customer perceives self-image to overlap with the brand [78]. It can be explained as a consumer's perception of oneness with a brand, which is a true and powerful manifestation of a person's search for identity and fulfilling value in the marketplace of brands [79]. One study found that, with actual or perceived group patterns, the identification process forcibly induces the repurchase behavior [80]. A recent study suggested that eWOM can also be influenced brand identification [81]. Moreover, the beneficial impact of brand identification on brand loyalty was heavily influenced by customers' perceptions of an apparel brand's sustainability activities [82]. With this viewpoint, this study investigated the effect of credible Sources and transparency about sustainability practices on brand identification. Thus, the following hypotheses were developed: Hypothesis 3a (H3a): Consumers exposed to sustainable brand positioning with credible sources will have a higher degree of brand identification than those exposed to no credible sources.
Hypothesis 3b (H3b): Consumers exposed to sustainable brand positioning with high transparency will have a higher degree of brand identification than those exposed to low transparency.

Electronic Word-Of-Mouth (eWOM)
Electronic Word-Of-Mouth is defined as the dynamic and continuing information exchange between prospective, existing, or former customers about a brand, product, or service that is available to diverse persons and institutions through the internet [83]. Several studies found that consumer attachment, trust, and identification were influenced by transparent and socially responsible brand initiatives, which foster positive eWOM [81,[84][85][86]. The messages on sustainability were found to favorably influence consumers' viewpoints, and awareness and boost eWOM [87,88]. Additionally, previous studies found that attachment, trust, and identification were elements of relationship quality [89][90][91]. Furthermore, relationship quality can have a positive impact on eWOM [92]. Thus, the following hypotheses were developed: Hypothesis 4a (H4a): A higher level of brand attachment will increase eWOM.
Hypothesis 4b (H4b): A higher level of brand trust will increase eWOM.

Hypothesis 4c (H4c):
A higher level of brand identification will increase eWOM.

Brand Loyalty
Brand loyalty is defined as a customer's unwavering allegiance to the brand and a close association with it that is unlikely to be harmed in normal circumstances [93]. It creates good feelings about the company in consumers' minds and a strong desire to buy the products/services from the same brand in the future [94,95]. Several studies found that disclosure of brands' sustainability efforts and transparency can positively impact brand loyalty [59,82]. Furthermore, previous studies found that brand loyalty can be influenced by brand attachment, trust, and identification among US national samples in the context of brand performance (market share), customer and brand relationship (cosmetic retail sector), and internet purchase intentions of machinery items [73,80,96]. Moreover, Zheng et al. [97] revealed loyalty can be attained by improving relationship quality. However, this study examined creating loyal Gen Zers by the effects of brand trust, attachment, and identification in the apparel sector with sustainability practices.
Hypothesis 5a (H5a): A higher level of brand attachment will increase brand loyalty.
Hypothesis 5b (H5b): A higher level of brand trust will increase brand loyalty.
Hypothesis 5c (H5c): A higher level of brand identification will increase brand loyalty.

Stimuli Design
This research was conducted using an online between-subject experiment. We developed eight conditions by using a 4 (No Credible Source/EPA as Credible Source/Social Influencers as Credible Source/Celebrity as Credible Source) by 2 (Low Transparency vs. High Transparency) factorial design ( Figure 2). Each participant was randomly assigned to one of the eight conditions in the online questionnaire on the Qualtrics survey platform.
We used an EPA logo to indicate the credible source for the conditions that used EPA as a credible source. For the conditions that use micro-influencers as a credible source, we asked participants to name their favorite social media influencers to examine microinfluencers influence. For public figure as a credible source, Ariana Grande was used in the experimental design because she is in the top ten list of most famous persons among Gen Zers [98] and has the most followers (294.4 million) on Instagram [99]. After viewing the stimulus, participants were asked manipulation check questions (Table 1). In terms of levels of transparency, message explicitness (vs. implicitness) levels were used to manipulate the High Transparency (vs. Low Transparency) conditions. This method was adopted from previous studies [61,62]. Table 2 describes each condition's experimental conditions and sample size in the final data analysis. We used an EPA logo to indicate the credible source for the conditions that used EPA as a credible source. For the conditions that use micro-influencers as a credible source, we asked participants to name their favorite social media influencers to examine microinfluencers influence. For public figure as a credible source, Ariana Grande was used in the experimental design because she is in the top ten list of most famous persons among

Research Instrument
The online questionnaire starts with an introductory page about the research description and the researchers' contact details. Then, each participant moved to the second section about their most and second favorite apparel brands, in-store and online shopping frequency and spending, social media usage, and social media platforms. Next, one of the eight stimuli was randomly assigned to the participants. After viewing the message in the condition, participants answered manipulation check questions, as well as the questions on Brand Trust [100], Attachment [101], Identification [79], eWOM [102], and Brand Loyalty [103]. A 7-point Likert scale (1 = strongly disagree, 7 = strongly agree) was utilized to measure participants' input. The research constructs can be found in Table 3. Then, the participants were asked questions about their sustainable brand choices. The last segment of the survey was about respondents' demographic characteristics, such as ethnicity, gender, education, and household income. The purchase from (piped text) will give me great pleasure I will find some comfort in buying or consuming from (piped text)

Trust
The products of (piped text) bring me security I have confidence in the quality of the products of (piped text) Choosing the products of (piped text) is a guarantee (piped text) is always sincere towards consumers (piped text) shows interest for its customers and society (piped text) is sensitive to consumer and societal problems Identification I feel a strong sense of belonging to (piped text) I identify strongly with (piped text) (piped text) embodies what I believe in (piped text) is like a part of me (piped text) has a great deal of personal meaning for me Table 3. Cont.

Constructs/Variables Statements
eWOM I will recommend (piped text) I will speak of good sides of (piped text) I will be proud to say to others that I am a customer of (piped text) I will strongly recommend people buy products from (piped text) I will speak favorably of (piped text) to others Loyalty I will say positive things about (piped text) to other people I will do more shopping on (piped text) in the next few years I will encourage friends and relatives to shop on (piped text) I will recommend (piped text) to community members who seek my advice I will consider (piped text) my first choice as a place to buy I am willing to pay more for (piped text) Sustainable apparel

Data Collection
A total of 393 random responses were collected from the online participants' recruitment site Prolific in January 2022. Prolific, an online research panel, was used in this study for many reasons, such as it offered low data collection costs for pre-set audience selection filters. The platform also provides transparency on available participants' numbers on each pre-set filter; data collection was fast, and it provided quality data [104,105]. This study collected data from United States Gen Zers because the US apparel market is the largest market in the world [1] and Gen Zers are the most influential customer group interested in sustainable products [6]. Thus, we used audience selection filters such as age (range from 18 to 24 years old), U.S. residence, people who shop online, and sex in the same proportion (male: 50%; female: 50%) for purposeful sampling.

Data Analysis
After completing data collection, responses were downloaded from Qualtrics, and data were reviewed and cleaned before proceeding to data analysis. Respondents who had not answered many questions, completed the survey in less than 3 min, did not answer their most favorite and second favorite brand, and did not have both in-store and online shopping experiences were not considered in this study. Finally, all participants' responses that did not pass the manipulation check questions (Table 2) were not included in the study. After data cleaning, there were 245 responses retained and analyzed in the present study.
Statistical Package for the Social Sciences (SPSS) version 28, IBM, New York, NY, USA. was used to conduct descriptive data analysis, Cronbach's alpha analysis, Pearson correlation, multivariate analysis of variance (MANOVA), and multiple regression analyses.

Sample Characteristics
Among the participants, 47.8% were female, 46.4% were male, 4.5% were non-binary/ third gender, and 3% of participants preferred not to say. The major ethnic backgrounds of respondents include White (53.5%). About 45% of participants had some college or associate degree, 59.2% were full-time students, 26.9% had an annual household income of $53,701 to $85,500, and 26.5% had an annual household income of $14,101 to $53,700. The detailed sample characteristics can be found in Table 4.

Preliminary Data Analysis
The mean and standard deviation, Cronbach's alpha, and Pearson correlations of constructs can be found in Table 5. All the variables had excellent internal reliability, with Cronbach's Alpha scores ranging from 0.91 to 0.96. Moreover, the results of the Pearson correlation indicated that all the variables were significantly correlated.

MANOVA
The impacts of eight experimental conditions were examined using a MANOVA analysis ( Table 6). The results suggest that the effect of Credible Source was significant on Brand Attachment (F (3237) = 5.00, p = 0.002), Trust (F (3237) = 3.18, p = 0.025), and Identification (F (3237) = 4.56, p = 0.004). These results concluded that H1a, H2a, and H3a were supported. However, the study found that High Transparency did not have a main effect on any dependent variables: Brand Attachment, Trust, and Identification. Thus H1b, H2b, and H3b were not supported (Figure 3). Identification (F (3237) = 4.56, p = 0.004). These results concluded that H1a, H2a, and H3a were supported. However, the study found that High Transparency did not have a main effect on any dependent variables: Brand Attachment, Trust, and Identification. Thus H1b, H2b, and H3b were not supported (Figure 3).  The Profile Plots of the findings are presented in Figure 4. It indicated that the participants had a significantly higher Attachment in condition 3 (Credible source-Social Influencer with Low Transparency) than in other conditions. Moreover, they had significantly higher Trust and Identification in condition 2 (Credible source-EPA with Low Transparency) followed by Condition 7 (Credible source-Social Influencer with High Transparency). This indicates sustainable positioning with the EPA logo, and Low Transparency achieves higher Brand Trust and Identification; however, social influencers' impact is higher on Brand Trust and Identification with High Transparency. The Profile Plots of the findings are presented in Figure 4. It indicated that the participants had a significantly higher Attachment in condition 3 (Credible source-Social Influencer with Low Transparency) than in other conditions. Moreover, they had significantly higher Trust and Identification in condition 2 (Credible source-EPA with Low Transparency) followed by Condition 7 (Credible source-Social Influencer with High Transparency). This indicates sustainable positioning with the EPA logo, and Low Transparency achieves higher Brand Trust and Identification; however, social influencers' impact is higher on Brand Trust and Identification with High Transparency.

Regression Analysis
Linear regression analyses were conducted to assess the impact of Brand Trust, Identification, Attachment to eWOM, and Brand Loyalty ( Table 7). The results suggested that Brand Attachment and Trust were significant predictors of eWOM and Loyalty. Thus, hypotheses H4a, H4b, H5a, and H5b were supported. However, Brand Identification only had a significant impact on Brand loyalty but not on eWOM. Thus, H5c was supported,

Regression Analysis
Linear regression analyses were conducted to assess the impact of Brand Trust, Identification, Attachment to eWOM, and Brand Loyalty ( Table 7). The results suggested that Brand Attachment and Trust were significant predictors of eWOM and Loyalty. Thus, hypotheses H4a, H4b, H5a, and H5b were supported. However, Brand Identification only had a significant impact on Brand loyalty but not on eWOM. Thus, H5c was supported, while H4c was not. Among the three predictors, Brand Trust was the strongest predictor for both eWOM (β = 0.55, p < 0.001) and Brand Loyalty (β = 0.48, p < 0.001).

Discussion and Conclusions
The results of this study verified that sustainable positioning with credible sources could significantly enhance participants' Brand Attachment, Trust, and Identification. Furthermore, the results revealed that Brand Attachment, Trust, and Identification positively affected Brand Loyalty whereas Brand Trust is the strongest predictor, which is consistent with previous research [73,80,96]. From Figure 4, it is apparent that sustainable positioning with EPA certifications achieved higher Brand Trust and Identification than other conditions of this research. This finding supports previous studies that affirmed third-party logos or certifications clearly influence sustainable communications promotion [53,106,107]. A previous study by Jun and Yi [108] found that social influencers can increase positive brand attachment, which can enhance brand loyalty. This study validated that sustainable positioning with social influencer endorsement had the highest impact on Brand Attachment than other conditions among Gen Zers. Moreover, this study's result was aligned with previous studies in terms of brand attachment, and identification can be influenced by brands' sustainability activities [70,82]. Thus, this research's main contribution is identifying apparel brands' sustainable positioning relationship with brand attachment, trust, and identification which leads to brand loyalty, and then showing how these dependable variables were affected by different credible sources.
This study examined the impact of credible sources on brand attachment, trust, and identification, which can increase eWOM. The results found that brand attachment and trust positively affected eWOM. The relationships of brand attachment and trust with eWOM were aligned with previous studies [68,85,[109][110][111][112]. However, surprisingly, this study could not find significant support from Brand Identification to eWOM as in previous studies [81]. The possible reason might be the participants understood the presented supply-chain sustainable causes in this study were important for them, but still, they were not ready to spread the word as it is their personal interest. This surprising result creates the need to conduct future research to investigate the reasons.
This research experimented with hangtag as an offline communication method with low transparency and social media posts as an online communication method with high transparency. Li and Leonas [113] discovered that communicating with consumers about ecologically friendly garments using hangtags may be more successful than using websites, although webpages provide more adequate details. In this study, social media posts had detailed information on brands' sustainability practices in the form of high transparency, but no difference was found with hangtag as a low transparency promotion medium; though, certifications and endorsements from different credible sources change the effectiveness of sustainable brand positioning.
This study investigated the effect of transparency on brand attachment, trust, and identification. However, we did not find consistent evidence as to previous studies [59,61,62], which noted the importance of transparency. A possible reason for it may be that transparency is a broad concept [114]. Many apparel brands promote transparency on sustainability about various issues (such as eco-friendly product usage, fair labor, and renewable energy usage) in many presentational formats. In addition, consumers may have a different level of knowledge and preferences on sustainability where they expect transparency. In this study, the presentation of transparency-related experimental conditions might not be aligned with participants' sustainability disclosure expectations which could be a possible reason for this conflict result.
Furthermore, this study looked into participants' sustainability preferences in more detail in search of practical implications. Participants were asked "if their most favorite apparel brand was not focused on sustainability but their second favorite brand is. Will they move to a sustainable apparel brand or stick to their most favorite brand?" The result in Figure 5 showed that 50% would move to a second favorite brand sustainable brand, and 50% would stick to their most favorite apparel brand. However, the results suggest that higher-income groups and females have a higher intention to switch to a more sustainable brand. A total of 64% of higher-income (income above $85,500) group participants had the intention to move to a sustainable brand, whereas only 43% of lower-income (income below $85,500) group participants had the intention. In addition, the results revealed that 58% of female participants would move to a sustainable brand, whereas only 42% of male participants had the intention.
conduct future research to investigate the reasons.
This research experimented with hangtag as an offline communication method with low transparency and social media posts as an online communication method with high transparency. Li and Leonas [113] discovered that communicating with consumers about ecologically friendly garments using hangtags may be more successful than using websites, although webpages provide more adequate details. In this study, social media posts had detailed information on brands' sustainability practices in the form of high transparency, but no difference was found with hangtag as a low transparency promotion medium; though, certifications and endorsements from different credible sources change the effectiveness of sustainable brand positioning.
This study investigated the effect of transparency on brand attachment, trust, and identification. However, we did not find consistent evidence as to previous studies [59,61,62], which noted the importance of transparency. A possible reason for it may be that transparency is a broad concept [114]. Many apparel brands promote transparency on sustainability about various issues (such as eco-friendly product usage, fair labor, and renewable energy usage) in many presentational formats. In addition, consumers may have a different level of knowledge and preferences on sustainability where they expect transparency. In this study, the presentation of transparency-related experimental conditions might not be aligned with participants' sustainability disclosure expectations which could be a possible reason for this conflict result.
Furthermore, this study looked into participants' sustainability preferences in more detail in search of practical implications. Participants were asked "if their most favorite apparel brand was not focused on sustainability but their second favorite brand is. Will they move to a sustainable apparel brand or stick to their most favorite brand?" The result in Figure 5 showed that 50% would move to a second favorite brand sustainable brand, and 50% would stick to their most favorite apparel brand. However, the results suggest that higher-income groups and females have a higher intention to switch to a more sustainable brand. A total of 64% of higher-income (income above $85,500) group participants had the intention to move to a sustainable brand, whereas only 43% of lowerincome (income below $85,500) group participants had the intention. In addition, the results revealed that 58% of female participants would move to a sustainable brand, whereas only 42% of male participants had the intention.

Theoretical Implications
This study adds empirical evidence to the apparel consumption context from the existing literature on cosmetics, brand performance, and machinery items. Moreover, this study provides practical evidence in applying the S-O-R theoretical model as a foundation in the area of sustainable positioning and its impact on brand attachment, trust, and

Theoretical Implications
This study adds empirical evidence to the apparel consumption context from the existing literature on cosmetics, brand performance, and machinery items. Moreover, this study provides practical evidence in applying the S-O-R theoretical model as a foundation in the area of sustainable positioning and its impact on brand attachment, trust, and identification which predicted eWOM and brand loyalty. Thus, this study delivered a significant theoretical contribution to the S-O-R model and described consumer behavior insights on apparel brands' sustainable positioning. The findings may inspire more empirical research on the relationship between how different brand promotions and sustainability-related activities may increase eWOM and brand loyalty through the influence of brand attachment, trust, and identification.
Moreover, applying the S-O-R model, this present research contributes to the body of knowledge on sustainable positioning, eWOM, and brand loyalty by illustrating the use of different Credible Sources. In this era of social media, many previous studies examined brand promotion techniques with social influencers and celebrities [54,57]. This study was focused on apparel brands' sustainability communication; thus, it developed and tested a conceptual model that emphasized the role of social influencers and celebrities and compared it with no and an agency as credible sources. It found that sustainability positioning with various credible sources had positive but different impacts on brand attachment, trust, and identification among Gen Zers. Although this study did not find any evidence that transparency had an impact on brand attachment, trust, and identification, it creates a research question to experiment with different types of transparency practices (such as eco-friendly products usage, fair labor, renewal energy usage) on various formats (such as websites, social media posts, videos) in future studies. Moreover, it offered evidence to the literature that women and higher-income groups prefer sustainable brands.

Practical Implications
The results of this study suggested that the impact of sustainable positioning with credible sources was significant on brand attachment, trust, and identification. Thus, from a management standpoint, sustainable apparel brands may provide reliable verification of their sustainability claims with credible sources. Even though previous studies assumed that credible sources could help to avoid the impact of greenwashing, the findings of this study suggested that brands should be more careful and strategic in communication as consumers may have different acceptance levels based on the various credible sources. For instance, regarding the brands' sustainability promotion by celebrities with high transparency, this study found that participants took it negatively as unnecessary information. The results of this study suggest that apparel brands that target Gen Zers may promote their sustainable practices by credible third-party agencies, and social media influencers and brands need to be tactical about information disclosure adequacy.
Moreover, this study found that sustainable brand attachment, trust, and identification are significant predictors of brand loyalty. Thus, from a practical standpoint, apparel brands should include these three determinants (brand attachment, trust, and identification) in the marketing strategy if they want to increase customers' brand loyalty. Furthermore, this study discovered brand attachment and trust have a significant positive impact on eWOM. In addition, from the findings based on Figure 4, this study found that brand attachment can be achieved by sustainable positioning with credible sources (social influencers) and brand trust can be gained by sustainable positioning with credible sources (EPA). Thus, apparel brands should be focused on sustainable positioning with credible sources to attain brand attachment and trust as well as to generate eWOM. This study supports that sustainable positioning can be crucial for apparel brands as Gen Zers are very concerned about the environment and society. Thus, brands should be focused on sustainable positioning to accomplish brand attachment, trust, identification, loyalty, and boost eWOM.
Additionally, the findings of this study discovered that the high-income group (above $85,500) and female consumers had higher intentions to move to sustainable brands ( Figure 5). Thus, apparel brands that target female and high-income consumers (such as luxury brands) may find the results useful. In sum, this study offers useful advice to practitioners by recommending that they pay close attention to sustainable positioning strategies.

Limitations and Future Research Suggestions
This study has a few limitations that propose future research opportunities. First, this study manipulated hangtags and Instagram posts as stimuli designs. Although we adopted the ideas from apparel brands' current sustainable positioning practices, the formats of manipulated messages might not properly reflect shoppers' experience and sustainable practice expectations. A future study might expand on our findings to examine how different information displays and channels (such as various hangtags, website information, social media post formats, news, email, blogs, videos, etc.) might have a distinct impact on consumers' perceptions in respect of sustainable positioning. Secondly, the result showed transparency did not have any impact on any dependable variables of this study; thus, different types of sustainability causes (such as eco-friendly products usage, fair labor, and renewable energy usage) and extended information can be experimented with to get insight into sustainable consumption behaviors.
Third, this study compared participants' most favorite apparel brand and second favorite brand to keep participants close acceptability level of these brands. Thus, future studies can be conducted with different types of brands, such as with an unknown brand vs. a fast-fashion brand or luxury vs. budget-oriented brands. Fifth, the study used a relatively small sample size of U.S. Gen Zers, which had some limitations. For instance, 24.1% of the study participants were Asians which is higher than the United States demographic percentages (In 2019, 6% of Gen Z in the United States were Asians; [115]. Thus, future studies with a bigger national representative sample and comparison among different age groups, demographics, and geographic locations will provide a more valid and comprehensive result.