Communicating Sustainable Shoes to Mainstream Consumers : The Impact of Advertisement Design on Buying Intention

Traditionally, marketing of sustainable products addresses green buyers, thus missing out on the mainstream consumers and volume necessary to cover the potentially higher cost of more sustainable materials. However, how to effectively communicate more sustainable products to mainstream consumers and to increase their buying intention is still underexplored. Combining personal and environmental benefits, called double benefit theory, is promoted as an effective green marketing strategy but so far not supported by quantitative research as being effective to reach mainstream consumers. We studied the effect of advertisement elements (layout color, benefit type, and heritage) on the products’ perceived sustainability, quality and fashion image, and buying intentions of mainstream consumers. Two hundred adults participated in a study that was based on a 2 (red vs. green layout) × 2 (personal vs. environmental benefit) × 2 (local vs. global heritage) between-subjects factorial design of a sustainable shoe advertisement. The impact of these independent variables on product image as well as on buying intention was analyzed by means of three-way ANOVAs. In line with the double benefit theory, combining a personal benefit with a green layout led to the highest buying intention. Moreover, a mediation analysis revealed the effect OPEN ACCESS Sustainability 2015, 7 8421 of emphasizing a personal benefit on buying intention was mediated by fashion image but not by sustainability. Sustainability, however, did have a positive effect on buying intentions independent of benefit type.


Introduction
Green marketing [1,2] has been a research topic for over thirty years [3,4].Focusing mainly on developing marketing strategies to approach the green consumer population, it was not meant or not able to attract the mainstream consumer.A study by the United Nations Environmental Program (UNEP) [5] (p.15) reports that only 4% of consumers actually buy sustainable products, this is in stark contrast with the 40% who stated that they were willing to buy more sustainable products.The Natural Marketing Institute published that, although 16% of the consumers indicate that they are willing to pay 20% more for a product that is produced in a sustainable and environmentally friendly way [6] (p. 4), in reality even fewer consumers deliver on that promise [7].The market for greener products is under-exploited by marketers [8].There appears to be a potentially much larger market for sustainable products if the mainstream consumer could be reached.This would make higher sales volumes possible, which are necessary to cover the potential extra cost to produce in a more sustainable and a more environmentally friendly way.Although there is extensive qualitative research in green marketing publicized [3,4], practical guidelines for the successful advertising of sustainable products substantiated by quantitative research are scarce, especially for marketing towards mainstream consumers.This makes effective advertising of sustainable products difficult.
We tried to bridge part of this knowledge gap with this research, performed as part of a project for the shoe manufacturer Bata Brands S.A. (further called "Bata") to develop the sustainable Bata shoe of tomorrow, targeting mainstream adults.Practical guidelines were needed to communicate the characteristics of the sustainable shoe collection in advertisements.The family-owned footwear retailer and manufacturer, founded in 1894 in the Czech Republic, operates on five continents.Striving to "think global, act local", the company designs, produces and sells most of its products in the emerging markets locally in addition to producing for the developed markets.Bata sells "value for money", serving in most countries the low and medium price segments of the market with a broad variety of shoes.Since its founding, the company has developed a heritage of being a socially responsible company; they have been building housing and schools for employees all over the world for many years.This long heritage on both a global and a local level is a unique feature among shoe producers.We took Bata as a case study to discover how to communicate a sustainable product effectively to the mainstream consumer.In our research, we investigated how graphical and textual elements of an advertisement for sustainable shoes can influence the perceived product image and the buying intention of mainstream consumers.

Green Marketing Evolves in Marketing Greener Products
Since the 1970s, green marketing has been the subject of many, mainly qualitative, research papers [4].In the literature, the marketing of sustainable or environmentally friendly products is often mentioned in combination with the terms "disappointing consumer response" and "mistrust" [2,9].Researchers were holding the industry responsible because "some organisations appeared to exploit" consumers' increased environmental awareness without modifying their products or processes and committed "green washing" (i.e., providing disinformation disseminated so as to present an environmentally responsible public image).In response, the introduction of eco-labels was promoted as a solution to make it easier for consumers to differentiate environmentally friendly products from the rest [10], based on the idea that better-informed customers would change their buying behavior [11].Still, many of these measures did not live up to the expectations with disappointing increases in sales volume of sustainable products.
Peattie [12] points out there is no such thing as a "green consumer", there is only green purchasing behavior; that is, only if products are otherwise equal the majority of consumers would prefer the green option.Most consumers are purchasing both "green" and "grey" (without environmental benefits) based on trade-offs not only between conventional issues like price and availability but also between green credentials like organic or recycled content [13].The view that there is no dedicated segment of green consumers is supported by Schuhwerk and Lefkoff-Hagius [14] who found that both low and high level environmentally involved persons do not differ in purchase intent for green laundry detergent, regardless of whether the advertisement focused on cost-saving or on environmental attributes.Following this result they concluded it unnecessary to separate advertising campaigns to target different segments of green consumers when selling sustainable products.
More recent publications therefore state that sustainable marketing should focus on the whole marketing mix (product, place, price and promotion) instead of on the products' sustainable specifications alone [9].When customers enter a (web) store, they first look for products that meet their basic needs, make them happy or feel attractive, taste good, perform well, and so on.When these qualities are met for the right price in the right place, consumers then seek products that best communicate their environmental beliefs to finalize their purchase decision.This layered decision-making process is described in the double filter theory [15].In line with this theory, quantitative research on eco-fashion by Niinimäki [16] showed eco-aspects can only add value to the product if the product is otherwise attractive, particularly in the fashion and luxury industry.Fashion is a challenging product category in sustainable marketing; consumers differ in their expectations and beliefs on how much impact their sustainable choice makes and how much effort their sustainable fashion shopping takes [17].For instance, the effort it takes may differ depending on whether one shops for casual or business attire based simply on the fact that sustainable options are more readily available for the former than the latter.Also, the impact a more sustainable option has on the environment might be perceived differently in both cases.
Ottman [18] was one of the first to recognize people seldom buy sustainable products for the sake of sustainability alone and therefore suggested to highlight the added consumer value over and above sustainability both in product attributes and in marketing.This is later referred to as linked [19] or double benefit [20], as in combining the sustainable product with personal benefits.Ottman names five typical personal benefits for sustainable products: efficiency and cost effectiveness; health and safety; performance; symbolism and status; and convenience.
The explanations and recommendations in the above-mentioned literature are valuable but abstract for practitioners in marketing, especially when marketing towards a larger mainstream consumer base rather than to green buyers exclusively.There is also little quantitative support that these theories lead to increased buying intentions, more sales, or higher prices, except for recent research on organic food [21] (p.172), which indicated that overall there is a significant willingness to pay on average 6% more for food products with an organic claim and that this percentage is higher for vice products (such as soft drinks and beer) than for virtue products (such as, dairy and vegetables).This finding is in contrast with average demanded price premiums of 30% for virtue and 60% for vice organic food products.
The research reported in this paper addresses the question of how to more effectively communicate sustainable value and thereby raise interest in sustainable products.Specifically, how elements of print advertisements can be manipulated to alter perceived product images and to increase consumers' buying intentions.

Advertising Sustainable Products
Advertisement designs use diverse graphical and textual elements, and impact, interaction and dependency of these elements is complex.However, three elements are frequently mentioned in research regarding the advertisement of sustainable products and were selected as our independent variables: Color of the layout (red vs. green), communicated benefit (personal vs. environmental), and heritage (local vs. global).

Color of the Advertisement Layout
An American research report [22] published a list of brands perceived as sustainable by American consumers.The brands have one common feature: All use the color green and natural graphics as a dominant graphical element in their advertisements.The use of abundant green vegetation and clear water is a universal standard in green advertising [23] and used to construct a positive sustainable brand image.However, the dominant color in traditional Bata advertisements has always been red, aimed at creating a cosmopolitan brand image.Therefore, the first independent variable is the effect of the color of an advertisement layout.Previous quantitative research by Hartman et al. [3] revealed a positive correlation between purchase intention and emotional (i.e., catering to the senses) green advertising.Thus we hypothesize; H1: When advertisements are based on a green layout as opposed to a red layout, participants will report higher buying intentions.

Environmental vs. Personal Benefit
People seek benefits from the products they buy.For sustainable products, these are likely both environmental (e.g., protect the environment) and personal.From the five suggested personal benefits related to sustainable products, as suggested by Ottman [18], healthy feet appear to be the most applicable personal benefit for the low and medium segment-positioned Bata shoe brand.Because of the low importance given to the environment as a buying criterion for shoes [20], we expect people to rather buy shoes on personal benefit than on environmental benefit.Thus, we hypothesize: H2a: When advertisements emphasize a personal benefit (e.g., "protects your foot health") as opposed to an environmental benefit (e.g., "protects the environment"), participants will report higher buying intentions.
One of the green marketing strategies mentioned in publications [18][19][20] is called the double-benefit strategy.This strategy proposes marketing of sustainable products to be more successful if the sustainability of the product (e.g., the green layout) is linked to primary personal benefits of individual consumers because the environmental benefit alone is seldom the main reason for buying a product.If the double-benefit strategy is valid, the buying intention will be highest when a green layout is combined with a personal benefit, thus addressing sustainability in an indirect way and the personal benefit directly.Thus, we expect: H2b: Participants report the highest buying intentions when presented with the personal benefit combined with the green layout.
An important aspect of sustainable products is that consumers can have negative associations with sustainable products [24]; consumers are not easily convinced that sustainable products are of good quality regardless of whether the product is a sustainable tire [25] or food with an organic claim [21].Luchs, Naylor, Irwin and Raghunathan [25] showed for tires that emphasizing the sustainability claim could result in a negative quality image.The high relevance of quality in the buying process of tires is similar to the high importance of the shoes' fashion image as a buying criterion for shoes [20].Also, Meyer [26] reported in his case studies (Coop NaturaLine organic cotton and Patagonia's Post-consumer recycled fleece) a lower perceived fashion image for eco-clothing.Thus, we expect: H2c: When advertisements emphasize an environmental benefit (e.g., "protects the environment") as opposed to a personal benefit (e.g., "protects your foot health"), participants will rate the shoes lower in its perceived fashion image.
One of the elements seen as making green marketing successful is that customers need to be convinced of the product's environmental benefits and its superior sustainability image [12] to consider buying it.The rationale of the emphasis on environmental benefit in green marketing is to help the consumer to better recognize the sustainable value of products [24].Thus we expect: H2d: When advertisements emphasize an environmental benefit (e.g., "protects the environment") as opposed to a personal benefit (e.g., "protects your foot health"), participants will rate the shoes higher in its perceived sustainability image.

Global vs. Local Heritage
Another phenomenon mentioned in the literature is the importance of heritage.According to Urde et al. [27] (p.5), heritage is "a dimension of a brand's identity found in its track record, longevity, core values, use of symbols and particularly in an organizational belief that its history is important"."Consumers search for authentic brands with genuine history in an increasingly global and dynamic marketplace" [28].Alexander [29] states "authenticity is enhanced by embedding the brand in a local culture".Bata has a heritage at both a local and a global level that, if correctly emphasized, might be a strong marketing instrument to increase buying intentions.Hustvedt and Dickson [30] found consumers of organic apparel also preferred to buy locally.Locally produce/production is a returning element in green marketing [31].We therefore explore as a third independent variable the effect of emphasizing either local or global heritage.We follow Alexander's line of thinking and hypothesize: H3: When advertisements emphasize local heritage as opposed to global heritage, participants will report higher buying intentions.

Methodology
To test our hypotheses we designed an experiment in which we manipulated advertisements for shoes along three dimensions: Color of layout, communicated benefit and communicated heritage.Experiments allow for strict control over extraneous and unwanted variables and for cause and effect interpretations of results [31,32].At the same time they come with the limitation of presenting the advertisements in a somewhat artificial setting.Nevertheless, former research [33,34] showed that even one-time exposure to advertisements in an experiment can be predictive of real life, in-market effects and an effective way to test the cause and effect relationships described in our hypotheses.

Participants
Six hundred university students received an invitation with a link to the online experiment.A total of 231 participants accepted the invitation (equaling a response rate of 38.5%) and were subsequently presented with one of the eight advertisements along with a questionnaire.The majority of participants were either master students or staff at a Dutch university.Thirty-one respondents were excluded due to incomplete answers.Consequently, the results of this study are based on the answers of 200 participants.The mean age was 24 years (SDage = 9) and 46% were women.Most of the participants (76%) were unfamiliar with Bata before the experiment.The participants did not receive any compensation, financial or otherwise.

Independent Variables and Stimuli
We designed a simple advertisement (see Figure 1) based on a 2 (color of layout: red vs. green) × 2 (communicated benefit: personal vs. environmental) × 2 (communicated heritage: local vs.global) experimental design that varied slightly for each factor combination (eight in total).The advertisements were designed as simple line drawings to avoid the confounding effects of style, material and color of the products as much as possible.The same drawing, depicting a men's and a women's shoe, was used for each factor combination.The setup and amount of information (both visual and textual) were the same for all eight advertisements.
To test whether the independent variables were perceived as intended when reading the advertisement variants we set up a pre-test questionnaire, which was also used as a manipulation check in the main experiment.The questionnaire was evaluated for validity by four experts (i.e., academics in the field of design for sustainability and marketing research) and filled in by 24 final year master students who were equally divided over the eight conditions (i.e., presented with one advertising variant per condition).The results of the pre-test mirror those of the manipulation checks reported in Section 4.1, indicating that the participants perceived the independent variables as intended: The advertisement with the green layout was perceived as more sustainable, eco-conscious and natural than the one with the red layout.Participants who read about the personal benefit were more convinced that the advertisement communicated a benefit for the individual consumer than participants who read about the environmental benefit.Participants who read about the local heritage were more convinced that BATA is embedded in the Dutch culture than participants who read about the global heritage.

Dependent Variables
Buying intention served as our main dependent variable for assessing the impact of the manipulations in the advertisements of our fictional sustainable shoe line.It was measured on a five-point scale, ranging from 1 = "I will definitely not buy" to 5 = "I will definitely buy these Bata shoes".
To be able to explain the effects in more detail and to check for potential moderation and mediation, we included several additional dependent variables measuring the perceived product image with regard to sustainability, quality and fashion.Based on the literature, we devised applicable scales to measure sustainability image [1,3,18,25], quality image [25,35] and fashion image [16,26] of shoes.Four experts evaluated the scales in terms of face validity and provided feedback to assure their suitability for measuring the effect of the advertisement elements.

Procedure and Design
The experiment was conducted online.Each of the respondents received an invitation to participate in the research via email that included instructions and a unique link to an online questionnaire.Participants were randomly assigned to a condition (i.e., one of the eight advertisements).Apart from the advertisements that differed across conditions, all participants received the same questionnaire, which was divided into four sections: (1) buying intention as the main dependent variable; (2) statements measuring the perceived sustainability, quality and fashion image of the product; (3) questions to check whether our manipulations of the independent variables were successful (see Section 3.3); and (4) demographics such as the participants' age in years, yearly shoe budget in EUR, number of shoes owned and prior familiarity with Bata.

Results
The results are presented in four sub-sections.In Section 4.1, we present the results of the manipulation checks.In Section 4.2, we present the results of a three-way ANOVA regarding the impact of layout, benefit type and heritage on buying intention.In Section 4.3, we present the results regarding the impact of the same variables on fashion image.In Section 4.4, we present the results of a mediation analysis in which we investigated fashion image and sustainability as potential mediators between benefit type and buying intention.

Manipulation Checks
Before testing our hypotheses, we checked whether our manipulations of the advertisements were successful (i.e., whether they really differed as intended according to the three factors sustainability of layout, communicated benefit and heritage).

Sustainability of the Layout
Perceived sustainability of the advertisements was measured with the following three items (on seven-point Likert scales, ranging from 1 = "strongly disagree" to 7 = "strongly agree"): "The graphical design of the advertisements emphasizes sustainability/communicates eco-consciousness/looks natural".The three items were combined (i.e., averaged) to form an index score after checking their one-dimensionality (all Principle Component Analysis (PCA) factor loadings > 0.87) and reliability (Cronbach's α = 0.90).The results revealed that our manipulation of sustainability based on the color used in the layout was successful: Respondents perceived the green layout to be more sustainable than the red layout (Mgreen = 4.77 vs. Mred = 2.85, t(180) = 9.56, p < 0.001).

Communicated Benefit
The communicated benefit of the advertisements was measured with the following three items (again on the same seven-point Likert scales): "The advertisement emphasizes a personal benefit for the customer/communicates a benefit for the environment (reverse coded)/emphasizes foot health" (communicated benefit).As before, the three items were combined to an index score after checking their one-dimensionality (all PCA factor loadings > 0.84) and reliability (Cronbach's α = 0.91).The results revealed that our manipulation of the communicated benefit was successful: Respondents receiving the advertisements with the personal benefit perceived the advertisement to be significantly more about communicating a benefit for the individual consumer compared the those being presented with the environmental benefit (Mpersonal = 4.12 vs. Menvironment = 2.78, t(177) = 7.45, p < 0.001).

Communicated Heritage
Finally, the type of heritage respondents ascribed to the advertisements was measured with the following item (on a seven-point Likert scale): "Bata is a company of Dutch heritage".The results here also revealed that our manipulation was successful: Respondents reading about the local heritage were more convinced of Bata's local Dutch origins than respondents reading about the global heritage (Mlocal = 4.95 vs. Mgobal = 3.11, t(180) = 7.68, p < 0.001).

The Impact of Layout, Benefit Type and Heritage on Buying Intention
The results of the three-way ANOVA revealed a marginally significant main effect for the type of benefit used in the advertisements, F(1, 179) = 3.06, p = 0.07.Buying intentions were higher for respondents presented with the personal benefit (Mpersonal = 2.36, SD = 0.84) compared to those presented with the environmental benefit (Menvironmental = 2.16, SD = 0.75).No main effects were found for the other two independent variables, the type of layout and heritage used in the advertisements, F(1, 179) = 1.07, p = 0.30 and F(1, 179) = 0.11, p = 0.75, respectively.
Moreover, the ANOVA revealed a significant interaction effect between the benefit and the layout in the advertisements, F(1, 179) = 5.82, p = 0.02. Figure 2 shows that when the green layout was combined with the personal benefit rather than the environmental benefit, buying intentions were significantly higher, 2.45 (SD = 0.76) vs. 1.95 (SD = 0.65), whereas no such effect was found for the red layout, 2.29 (SD = 0.92) vs. 2.36 (SD = 0.79).

The Impact of Layout, Benefit Type and Heritage on Fashion Image and Sustainability Image
Perceived fashion image of the product was measured with the following three items (on seven-point Likert scales, ranging from 1 = "strongly disagree" to 7 = "strongly agree"): "Shoes of the Bata footwear collection are fashionable/cool/a must-have".After checking their one-dimensionality (all PCA factor loadings > 0.82) and reliability (Cronbach's α = 0.83), they were combined to an index score.
The following three items were used to measure the perceived sustainability image of the product (on seven-point Likert scales): "Shoes of the new Bata footwear collection are sustainable/do not harm the environment/protect the earth".The items were combined to an index score after checking their one-dimensionality (all PCA factor loadings > 0.74) and reliability (Cronbach's α = 0.72).The results of the three-way ANOVA revealed no significant main effects for type of benefit, for color of layout or for heritage.

Mediation by Fashion Image and Sustainability Image
For checking possible mediation effects through fashion image and sustainability image, we conducted an ordinary least squares path analysis (using Preachers' SPSS Process script [36] Model 4).
The analysis revealed a significant indirect effect of benefit type on buying intention through fashion image (c = −0.09,CI (−0.20, −0.02)).Participants presented with the personal benefit rated fashion image higher than those presented with the environmental benefit (95% CI (−0.7300, −0.0731)).
The analysis revealed no significant indirect effect of benefit type on buying intention through sustainability image, due to a non-significant direct effect of benefit type on perceived sustainability image (a = −0.19,t = −0.38,p = 0.70), as was shown already in the results from the three-way ANOVA (see Section 3.2).However, we found a significant positive impact of sustainability image on buying intention (b = 0.113, t = 2.322, p = 0.0214) that was independent of the communicated benefit type.
The mediation model presented in Figure 3 shows that benefit type did not directly impact buying intention but that it did so indirectly through fashion image.The model can explain 20% of the variation in buying intention.

Discussion
In this section, we first discuss the results and theoretical implications pertaining to our hypotheses from Section 2, followed by limitations and suggestions for further research and a discussion of implications for marketers.

Impact of the Color of the Layout on Buying Intention
Previous research by Hartmann et al. [3] showed purchase intention to correlate both with what they called emotional (i.e., catering to the senses) and functional (i.e., catering to the rational mind) green advertising strategies.Specifically, in their research they manipulated a print advertisement of a low emission car either by placing it pictorially against the backdrop of pristine nature (in line with an emotional positioning strategy) or by including a tagline emphasizing its low CO2 emission levels (in line with a functional positioning strategy).We found no support for Hartmann's conclusion that buying intention for sustainable products is increased by the use of an emotional advertising strategy, in our case a green layout.Buying intention was similar for respondents presented with the green and the red layout, despite the fact that only the green layout was associated as standing for sustainability in the manipulation checks.H1 therefore was not supported by our results.The lack of effect from the green layout may be explained by the low importance sustainability tends to receive as a buying criterion [16,20] for clothing.

Impact of the Communicated Benefit on Buying Intention
Our results further showed a marginally significant effect of our second factor, benefit type, on buying intention.Participants being presented with the personal benefit reported higher buying intentions than those being presented with the environmental benefit, thus showing some support for H2a.An environmental benefit is a less important buying criterion than a personal benefit and likely the cause for the lower buying intention [20].However, the effect on buying intention by the personal benefit used in the advertisements (i.e., "these shoes protect foot health") was relatively low in absolute terms (i.e., slightly under the mid-point of the five-point Likert-scale, Mpersonal = 2.36, SD = 0.84).Apparently, "healthy feet", despite being more important than an environmentally framed benefit, is not that relevant as a buying criterion among our relatively young respondents.We expect references like "make you look good", "latest fashion", or "good for dancing" would have led to even higher buying intentions.As shown by the significant mediation, emphasizing an environmental benefit negatively affected the buying intention through a lower perceived fashion image of the product; this coincides with the conclusions Meyer [26] drew from his case studies in which eco-fashion was perceived less fashionable.

Interaction between Color of Layout and Communicated Benefit
Previous research [11,19] suggested that buying intention for sustainable products might be higher when both environmental and functional benefits are combined.We found this proposed interaction, in our case between the independent variables "layout" and "benefit type", to be significant: Buying intention was highest when combining either the personal benefit with the green layout or the environmental benefit with the red layout.Combining the environmental benefit with the green layout led to the lowest buying intention, 20% lower than in the highest rated combination of personal benefit with a green layout.Our findings thus support H2b and substantiate the claimed effectiveness of the double benefit theory [11,19] as a strategy in increasing interest for sustainable products.According to the double benefit theory, it is best to sell sustainable products on personal benefit and to combine it with an environmental message catering to the senses, in our case the green layout.

Impact of the Communicated Heritage on Buying Intention
We expected that respondents presented with an advertisement emphasizing local heritage as opposed to global heritage to report higher buying intentions.Based on our results, we found no significant difference in buying intentions due to heritage and thus no support for H3.This finding contradicts other research [27,28] that found consumers of sustainable products prefer locally produced products over globally produced ones.We suspect that this might have to the do with the product category of shoes, where local heritage might not be of similar importance, either in general or for our relatively young respondents.Other heritage elements like the historical aura surrounding the brand or references to social responsibility might give other results.Another factor why heritage revealed no differences might be due to unfamiliarity with the brand-our results showed that only one out of four respondents was familiar with BATA.Given that heritage requires deeper knowledge about the brand, results might be different for a well-known brand.

Impact of Communicated Benefit on Fashion Image and Sustainability Image
Fashion appeal is the most important criterion when buying shoes, comparable to the importance of quality in buying tires [25].We therefore expected fashion image to be negatively impacted by an emphasis on environmental benefits (see H2c), just like an emphasis on sustainability negatively impacts the perceived quality of car tires.The results support this hypothesis: Emphasizing the environmental benefit resulted in a significantly lower perceived fashion image compared to emphasizing the personal benefit.This is in line with the reported lower fashion image of eco-clothing in Meyers' case studies [26].
We expected that communicating an environmental as opposed to a personal benefit would lead to a higher sustainability image of the product (see H2d).We found no support for this hypothesis in our results.This suggests either the direct environmental benefit claim was not believed or not considered important for the product category of shoes.The first explanation can be ruled out by our manipulation checks, which clearly showed that respondents who received the advertisements with the environmental benefit claim also perceived it to be significantly more about communicating a benefit for the environment than for the individual consumer (and vice versa for those who received the advertisement with the environmental benefit claim).The second explanation seems more likely as sustainability has previously been identified as being of low importance as a buying criterion for the product category of shoes [20].

Mediation of Fashion Image and Sustainability Image on Buying Intention
Based on previous research that found the appearance of the shoe to be the most important buying criterion when buying shoes [20] and clothing [16], we expected that our dependent variable fashion image would exert a great influence on buying intention.By the same token, as environmental concerns are typically not the most important buying criterion when buying shoes [16,20], we expected a lower influence on buying intention through sustainability image of the shoe.The results from the mediation analysis support this and further our understanding of the mechanisms involved in raising consumers' interest in sustainable shoes through the communicated benefit.Our model could account for 20% of the variation in buying intention, despite the fact that the drawings presented to the respondents remained rather sketchy.It is quite possible that the added richness in detail of a photograph or of seeing the actual shoes in front of you would influence buying intentions even stronger.
The fact that sustainability image has a direct effect on buying intention independent of the communicated benefit suggests consumers apply a double filter [20].The more important buying criteria must be satisfied first, in our case fashion image but also price and brand.When more buying options remain, only then sustainability comes into the equation and increases the buying intention of the sustainable option.Our data unfortunately offer no answer on how to create a sustainability image.Sustainability image was neither significantly impacted by layout nor benefit nor heritage.

Limitations and Further Research
Although previous research [33,34] showed that even one-time exposures in a controlled environment can be predictive of in-market effects in real life people, additional testing in a more natural environment is advised to validate the cause and effect relationships found in our controlled experiments.In real life, people are usually exposed to advertisements for a much shorter time.Therefore one should not conclude that one exposure would be enough to create the same effects, especially as people might attend to the advertisements differently (e.g., less consciously when distracted by another task carried out simultaneously).
This research focused on shoes, a product category where sustainability is of low importance compared to other buying criteria [20].However, for other products such as food or baby nutrition, where the environmental benefit is more directly connected to health, sustainability is of higher importance, and can increase willingness to pay, as shown by Van Doorn and Verhoef [21].
As the respondents recruited for this research were mainly master students at a University in the Netherlands, they were relatively young.It is thus unclear whether an older population would show the same results; the literature differs in the effect of age on sustainable behavior and consumption [37].In particular, brand familiarity with Bata was relatively low among our young respondents.A well-known brand for this younger cohort might show different results, given the more readily available associations of its (sustainable) brand image.
Furthermore, the interpretation of advertisements-e.g., how color is linked to perceptions of sustainability-is assumed to depend on culture [38] and/or region; thus, caution should be used when implementing the findings on a global scale.Certainly, in further research it would be interesting to investigate the impact of geography and culture on the importance and perception of sustainability in products or brands.
Another avenue for further research is the different benefits people seek by products.We selected "foot health" as the personal benefit; however, other personal benefits might have stronger effects on the evaluation of a brand and product.For instance, emphasizing a fashionable image as a personal benefit might have a more noticeable impact on buying intention.After all, the looks of the shoe are likely the most important criterion when buying shoes.How to effectively use different personal benefits to increase buying intention of sustainable products asks for further research.Our mediation results provide new ideas for further research and marketing theory development on how to create value with sustainable products for mainstream consumers.
Finally, further research may investigate the question of how to create a sustainable image.We showed a direct effect of sustainable image on buying intention but were not able to pinpoint what created the sustainability image of the shoe.A specific mentioning of the environmental benefits would lead to a lower buying intention through fashion image.A potential answer might be found in the interaction between layout and benefit.

Implications for Marketers
The results of our analysis offer interesting insights into how to increase the buying intention of mainstream consumers for sustainable shoes, as well as how to avoid alienating mainstream consumers when bringing sustainable products to the market.
Advertisements for sustainable products typically feature green colors and abundant natural sceneries [22].Our results showed that although people perceived our green natural layout as standing for sustainability, this did not result in a more sustainable product image of our shoe compared to the red cosmopolitan version.On the contrary, when combining a green layout and communication about environmental benefits in the advertisement, buying intentions were significantly lower.This shows overemphasizing the sustainability of sustainable products can easily become too much of a good thing.
Focusing the communication on personal benefits and embedding this in a green layout, as proposed by the double benefit theory [18][19][20], resulted in higher buying intentions.This is owed to a third variable, namely fashion image, which mediates between the (communicated) benefit claim and buying intentions.That is, emphasizing an environmental benefit, instead of a personal benefit, reduced fashion image, which in turn reduced buying intentions.This result is interesting in its own right since we communicated foot health as a personal benefit and did not mention or refer to fashion in our advertisement.By communicating on personal benefit it is thus possible to increase buying intention through fashion image.
Moreover, even though the type of benefit-personal vs. environmental-did not influence sustainability image, the latter is still relevant as it directly influences buying intentions.However, given that the effect of sustainability image is smaller than the effect based on the communicated benefit through fashion image, sustainability image should not be prioritized at the expense of more important buying criteria such as fashion appeal and health benefits.

Conclusions
Our research found it is possible to effectively communicate sustainable products to mainstream consumers.Based on our results, and other than suggested by the widespread use of green layouts to communicate sustainable products, using a green layout was not effective in increasing buying intention of shoes on its own.However, focusing communication on personal benefits as opposed to environmental benefits on its own did lead to a higher buying intention.Moreover, combining a personal benefit with a green layout led to the highest buying intention.Thus, our results provide previously missing empirical evidence in support for the double benefit theory [18][19][20] as an effective strategy to increase consumers' interest in sustainable products.
Furthermore, a mediation analysis revealed the effect of emphasizing a personal benefit on buying intention was mediated by fashion image but not by sustainability image.Sustainability image, however, did have a positive effect on buying intentions independent of benefit type.

Figure 3 .
Figure 3. Model of benefit type as predictor of buying intention, mediated by fashion and sustainability image.The bias-corrected bootstrap confidence interval (CI) for the indirect effect is based on 1000 bootstrap samples.