Promoting Plant-Based Sustainable Diet to Support Future Development: Emotional Design Card Development

Abstract

The quest for a plant-based sustainable diet has significant value for promoting future development, posing novel challenges for designers. This study involved a five-step design process, encompassing a case study, an experimental study, prototype conception, user testing, and design refinement, with the aim of developing a “Plant-based Sustainable Diet 3P Emotional Design Method” card set that enables individuals to devise personalized sustainable diet plans. The results demonstrated that the instinctive level originates from the product itself, signifying the efficacy of sensory design cues for plant-based foods. The behavioral level stems from the interactive content generated by the product, denoting the efficacy of design cues and highlighting the advantages of transitioning to healthier ingredients for the body. The reflective level arises from the reflection and contemplation of the product, signifying the efficacy of value perception and design cues pertaining to economic, environmental, and social sustainability knowledge. The study analyzed the influencing factors of diet choices through emotional design and provided insights into the underlying psychological mechanisms. The theoretical contribution of this study lies in the novel integration of emotional design and sustainable diet research, while its practical contribution is the introduction of methods and tools that facilitate the adoption of plant-based sustainable diet practices at the individual level.

1. Introduction

Sustainable development imposes novel requirements on designers and design practitioners to integrate sustainable factors into future product design and development and to devise more sustainable design methods and tools [1]. Although there exists a profound linkage between daily diet and sustainability, prompting the Food and Agriculture Organization of the United Nations to introduce the concept of sustainable diet [2]; comprehension of design elements pertaining to food remains nascent, particularly in relation to methodologies of food design and sustainability [3], which are still comparatively rare. Zampollo [4] posits that sustainability encompasses all aspects pertinent for food design, serving as the overarching principle and ultimate objective of food design. However, the existing research still lacks a systematic analysis regarding the integration of sustainability with diverse aspects of diet. The pervasive nature of the food system presents a contemporary challenge in concurrent contemplation of sustainability considerations [5].

Emotional design posits that integrating aspects of users’ mental activity into the design process has the potential to evoke diverse associations and emotional connections [6]. Diet, being an integral component of daily life, exerts a constant influence on individuals’ mood and deeper emotional states [7]. Consequently, harnessing individuals’ emotional dispositions towards food as a means to promote adoption of more sustainable diet practices has emerged as a viable approach. Currently, food-related emotional design is predominantly focused on product packaging, while the design of the food itself receives less attention [8]. The present study aims to forge an emotional bond between diet and sustainability, with food as the focal point, thereby contributing to the promotion of sustainable diet.

Card sets have been extensively utilized as an effective tool for emotional design, capable of clarifying directions, inspiring new perspectives, and bridging gaps [9]. In regard to diet, a highly personalized and flexible design issue, the development of a card set that enables individuals to design their own diet plans is anticipated to be more effective than a standardized recipe guidance plan [10]. Consequently, this study aims to design and formulate an emotional design card set, not solely intended for food producers or designers, but rather with the objective of guiding the creation of a sustainable diet plan for each individual, thereby promoting sustainable diet in support of future development. Furthermore, this study endeavors to broaden the overarching significance of design, aiming to foster the generation of ideas for each individual, thereby validating the potential of design [11].

In summary, the aim of this study is to devise an emotional design card set that facilitates the adoption of a sustainable diet. The card set serves as a tool to assist individuals in creating personalized or collaborative sustainable diet plans. The development of the card set comprises five key steps. First, we analyzed exemplary cases of implementing sustainable concepts, identifying pioneering areas related to diet and sustainability. Michelin Green Star restaurants were selected as the case study because these have effectively inspired consumers to adopt sustainable practices. Second, we conducted an experimental study to extract relevant factors from the identified categories, integrate them with emotional levels, and assess their impact on food choice intention. Third, we created a prototype of the card set and designed the cards based on the derived conclusions. Fourth, user testing was performed to evaluate the prototype, enabling users to utilize the cards and offer suggestions for improvements. Fifth, the design was refined to yield the “Sustainable Diet 3P Emotional Design Method” card set. The study innovatively integrates emotional hierarchy and sustainable diet research at the theoretical level, exploring the psychological mechanisms underlying dietary choices. Practically, this study offers methods and tools to advance the concept of sustainability on a personal level.

2. Literature Review

2.1. Sustainable Diet

FAO [2] has defined sustainable diet, that is “diets with low environmental impacts which contribute to food and nutrition security and to a healthy life for present and future generations; protective and respectful of biodiversity and ecosystems, culturally acceptable, accessible, economically fair and affordable; nutritionally adequate, safe and healthy; while optimizing natural and human resources”. A plant-based diet is considered a typical model of sustainable diet and has been extensively studied and promoted internationally [12]. In 2020, The World Resources Institute [13] defined plant-based foods as “Foods derived from plants and fungi rather than animal sources. This includes fruits and vegetables, beans, grains, legumes, mushrooms, nuts and seeds, plant oils, herbs, and spices”. Therefore, plant-based foods, nutrition, and health, together with economic, social, and environmental sustainability, are deemed representative of plant-based sustainable diets, and the current study aims to develop a design utilizing these core components.

In promoting the practice of sustainable diet, many governments have conducted large-scale surveys to assess citizens’ comprehension and receptiveness towards sustainable diet. It has been observed that there is a lack of comprehensive understanding of the concept of sustainable diet, and this is coupled with a misunderstanding regarding the relevance of certain key concepts [13]. Scholars have examined methods to promote sustainable diet from various perspectives: engagement-based measurement of consumer health and motivation [14], the identification of healthier, environmentally friendly, and cost-effective diet based on current consumption trends [15], and the compilation of tools to analyze methods that harmonize individual, community, and global health [16]. However, the conclusions derived from existing research are fragmented, thus posing challenges to balancing the multifaceted aspects of diet.

Although the scope of diet-related content is acknowledged, comprehensive considerations implemented in practice remain limited. For example, Michelin has not yet established specific metrics for evaluating restaurants’ contributions to sustainable development in awarding the Green Star, with the intention of fostering diverse sustainable practices (https://guide.michelin.com/en/article/sustainable-gastronomy/the-michelin-green-star (accessed on 21 August 2024)). The GOOD FOOD FUN’s practice in China outlines eight aspects for dietary initiatives, including plant-leading, healthy dietary habits, and waste reduction (https://www.goodfoodchina.net/en/updates/114 (accessed on 21 August 2024)). These initiatives have been applied to numerous project developments. However, there remains a scarcity of theoretically grounded, comprehensive research, particularly in exploring the internal psychological mechanisms that influence sustainable diet choices. The present study aims to address this gap in research.

2.2. Emotional Design

Emotional design postulates that emotions should be incorporated into product design, and that human brain activity can be categorized into three distinct levels: the innate instinctive level, the behavioral level that governs daily bodily functions, and the reflective level that is processed by the brain. Each of these levels encompasses the design of corresponding product expression content [6]. The instinctive level comprises the design of the product’s initial sensation, involving factors such as color, shape, and tactile sensation. The behavioral level pertains to the design of product usage and interaction functions, such as interaction mechanisms and feedback systems. The reflective level addresses the design of values-based thought processes, such as simulations of objects and reflections on social phenomena [17].

Currently, the implementation of emotional design in diet incorporates the utilization of aesthetics in food styling to heighten the appeal of food at the instinctive level [18], and employs default options or quantities to elevate the likelihood of particular food choices at the behavioral level [19], as well as considering intrinsic motivation and self-reflection in making diverse food choices at the reflective level [20]. However, current research lacks an integrated approach that considers promoting sustainable diet from three emotional levels, particularly the impact on distinct emotional levels under mental simulation conditions. In the context of imagination, pre-decision mental simulations have been suggested as being pivotal to diet decision shifts [21].

The multidimensional characteristics of sustainable diet are determined by closely related and interdependent factors and effects. In this context, it is particularly important to design and identify leverage points that promote a transition towards more sustainable diets and convey convincing information to consumers [22]. Emotional design can be an effective tool to influence diet choices by integrating elements of users’ mental activity, facilitating associations and resonance between product cues and user perceptions, and ultimately influencing the final decision [6]. However, there is a current scarcity of comprehensive research utilizing emotional design to influence dietary choices, and a specialized tool for this purpose is nonexistent. This study aims to conduct a more comprehensive analysis and develop tools to enhance an individual’s choices of sustainable diet.

2.3. Design Cards

A card set pertains to the utilization of prompts and inspirations for creative generation, structural organization, knowledge integration, and other content, facilitating a smoother progression of the design process [23]. An advantage of using cards lies in their capability to enhance the visibility, specificity, and intuitiveness of the design process. Cards offer a comprehensive view of information and exhibit flexibility in comparing, evaluating, and amalgamating elements, particularly in fostering the generation of innovative ideas [9]. However, there is also a problem of limited guidance and evaluation of specific implementation plans. In summary, cards are frequently utilized for inspiring creativity, primarily assisting designers in reorganizing pertinent information and setting priorities, while also facilitating communication among multiple stakeholders through a shared vocabulary. As a cost-efficiency and highly flexible design tool, cards are widely utilized in various design decisions and are deemed a “powerful ideation tool for any creative project” [24].

In relation to the development of food-related card sets, Lee et al. [9] developed a collection of thematic cards outlining significant domains related to food, thus facilitating designers’ integration of multidisciplinary perspectives for deliberations on associated design concepts. Zampollo and Peacock [3] developed the ‘Thoughts for Food’ card set for chefs’ generation of design content during the food preparation stage. In regard to the development of emotional design tools, Wu et al. [25] formulated a toolkit used by designers encompassing the steps and specific applications of emotional design methods across various stages. However, there exists a dearth in the development of card sets that can be used at the individual level, particularly in employing emotional design to promote personal sustainable diet choices.

This study aims to develop a card set at the individual level titled “Plant-based Sustainable Diet 3P Emotional Design Method”, inspiring consumers to use the card set and design their daily diet plans. By integrating emotional design with the definition of sustainable diet, it explores the factors that influence food choice intention and the conditional factors that trigger corresponding psychological mechanisms, specifically at the instinctive, behavioral, and reflective levels. Drawing upon the findings, the card set is designed to enhance awareness of sustainable diet, foster and stimulate creativity, make implicit concepts explicit, construct and organize ideas, facilitate engaging collaborations [26], and ultimately enable individuals to design their own personalized diet plan.

3. Materials and Methods

To facilitate the design of individual sustainable diet plans, the study progressed by developing a card set through five steps (Figure 1). First, a case study was conducted on the Michelin Green Star restaurants to analyze their implementation of sustainable concepts and consumer recognition, and based on dining experience, sustainable categories were identified that bridge the perspectives of consumers and producers. Second, utilizing emotional design principles, the sustainable themes from the previous step were classified into three distinct emotional levels. Variables influencing dietary choices were analyzed through experimental study. Third, a card prototype was designed based on the findings of the preceding steps. Fourth, the prototype of the card set was tested, and users were invited to share their experiences in using the cards, providing valuable optimization suggestions. Fifth, by integrating the improvement suggestions, the definitive “Sustainable Diet 3P Emotional Design Method” card set was developed. Next, the implementation process of each step is described.

The first step is about a case study on Michelin Green Star restaurants. The Michelin star rating is a globally esteemed gastronomic accolade sought after by chefs [27]. It was created in 2020, specifically to acknowledge restaurants that provide high-quality cuisine adhering to ethical and environmental standards [28]. These restaurants are pioneers in sustainable dining experiences, and analyzing their successful practices aids in staying abreast of the latest trends in sustainable diet. Searching for Michelin Green Star restaurants on the Michelin official website, the page presents detailed information about these establishments (https://guide.michelin.com/en/restaurants/sustainable_gastronomy (accessed on 21 August 2024)). Among these, the section titled “Gastronomy & Sustainability” outlines the restaurant’s dedication and activities towards sustainability, while ”MICHELIN guide’s point of view” outlines consumers’ feelings during the consumption process, including their perception of the restaurant’s sustainable ethos. Employing thematic analysis methods, the case study analyzed the “Gastronomy & Sustainability” and “MICHELIN guide’s point of view” sections on restaurant website pages, thereby identifying emerging sustainable themes based on dietary experience [29]. Step 1: Familiarizing with data. Transcribing data, reading and rereading the data, and recording initial ideas by splitting the data into units of analysis (e.g., sentences). Step 2: Generating initial codes. Initial coding involves extracting relevant concepts and features from the text and grouping them into associated themes. Step 3: Shearing for themes. Sorting the codes into sub-themes and then classifying them into broader main themes based on relationships between the sub-themes. Ensure that all relevant data are organized under each main theme. Step 4: Reviewing themes. Checking if the identified themes work in relation to the coded extracts and the entire dataset. Step 5: Defining the themes. Developing clear and concise names for each main theme. Finally, the themes were classified according to the definitions of sustainable diet and emotional design. After obtaining the theme, integrate it with the emotional level to analyze the theme with the emotional dimension, conduct literature analysis, and formulate research hypotheses for the relevant nutritional elements.

The second step involves conducting preliminary user research through online experiments. Drawing upon the definition of emotional design, factors influencing food choice at each level are designed to address the instinctive, behavioral, and reflective levels, and these are then tested. The experimental design content is shown in Figure 2. Primarily, the instinctive level focuses on the product itself, considering the sensory stimulation derived from plant-based foods [30]. At the behavioral level, the product generates interactive content, considering the benefits that adopting healthier ingredients can offer to the body [31]. The reflective level incorporates reflective thinking into design, considering the impact of economic, environmental, and social sustainability contexts on value perception [32]. The experimental outcomes were used to determine the theme of the card set. Participants were recruited on the online experimental platform Credamo, and a total of 11 experiments were conducted, involving 4448 people. The experimental materials consisted of two components—pictures and text. The pictures were used to demonstrate plant-based foods and sourced from plant-based dishes provided by Michelin Green Star restaurants. The text served to stimulate participants’ mental simulations, and its content was derived from reviews in food apps and case experiences. Prior to each experiment, predictive tests were undertaken to ascertain the efficacy of the experimental materials in relation to the test indicators. At the instinctive level, four experiments manipulated mental simulations of five senses (visual, auditory, olfactory, gustatory, and tactile) [33] and their impact on perceived attractiveness and choice intention. The experiments further analyzed whether the process was influenced by the number of diners and dining perspectives [34]. At the behavioral level, four experiments manipulated mental simulations of the impact of nutrient replacement on physical health perception [35], dietary fiber, protein, carbohydrates, and fat, on health perception and choice intention. It also analyzed whether the process was influenced by mental simulation and simulation pros and cons [36]. At the reflective level, three experiments manipulated mental simulations of food-related sustainable contexts [37], specifically economic, social, and environmental influences on sense of self-worth and choice intention. We analyzed whether the form of textual and pictorial descriptions has an impact on this process [38].

The third step involves designing the prototype of the card set, which corresponds to the outcomes of the first and second steps, and developing the thematic content of each card. According to the emotional design level, the card is divided into three parts, with five themes proposed for each part. The content design incorporates elements such as color, format, logo, and questions. Incorporating the definition of emotional design and considering the design content of experimental materials is the second step. At the instinctive level, the “product” content was designed to harness the sensory stimuli afforded by plant-based foods. At the behavioral level, the “promotional” content was designed to leverage the conclusions pertaining to the health benefits of nutritional elements. At the reflective level, the “benefit” content was designed to utilize the self-worth stimulus of sustainable content. For each theme, a logo was designed to visually represent and identify the concept [39].

In the fourth step, the prototype of the card set was tested, inviting various representative user types to reflect upon the content of homemade meals and receive feedback and suggestions. Users were surveyed on their perceptions and reflections regarding the outcomes of the card set at various levels, including improvements to current meals and aspirations for future food designs. Thirteen probationary users were recruited for online interviews, each lasting no less than 40 min [40]. The basic information of the participants is presented in Appendix A. Participants were first invited to imagine preparing meals for a specific occasion, noting down the meal content and the rationale behind it. They had discussions with the testers, and the contents were recorded by the recorders. Next, they were instructed to carefully review the card set. Then, they were prompted to discuss the content in the card set that interested them, considering whether it had sparked ideas to enhance their prepared meal and to articulate their reasons. We also inquired about novel insights pertaining to food elicited by the card set, recalling our aspirations for future food design. Concurrently, the influence of the card set’s content on the participants’ food choices for the next week was examined via interviews. Firstly, we asked the participants to write down their plans for food selection for the next week and asked them about the reasons for their choices. We also asked them about the differences between these plans and previous ones, in addition to examining the modifications influenced by the card set. Next, we asked participants to record their actual food choices made in the following week. Finally, participants offered suggestions for the card content and condensed the essential information.

The final stage of card set refining design to accord with user feedback from user testing yielded a finalized card set for individuals to design their personalized plant-based sustainable diet plans. This entailed incorporating a more detailed elaboration of the definition of sustainability, along with an introductory guide on utilizing the cards.

4. Results and Analysis

4.1. Case Study—Michelin Green Star Restaurants

4.1.1. Results

Through the five steps of thematic analysis outlined above, themes pertaining to sustainable design and the dining experience were derived from the production and consumption perspectives, respectively. Additionally, all articles related to sustainability from the Michelin website were collated and reviewed, and multiple data sources were analyzed to ensure that no new themes emerged and theoretical saturation was reached. By organizing and coding data collected from 380 Michelin Green Star restaurants, five emerging categories pertaining to sustainable diet have been delineated. “Plant-based foods and experiences” indicates the importance of enhancing comprehension and experimentation with plant-based foods, for example “We choose our produce very carefully in both quality of flavour and sustainability aspects (p63-1); Here, chef offers a single tasting menu (long or short, the choice is yours) which changes on a regular basis, and which focuses on the seasons and an almost exclusive use of ingredients from his own kitchen garden (c319-2)”. “Health and knowledge-based education” indicates the potential influence of diet on health and promotion of further research into sustainable knowledge, for example “I am as concerned about the health of my guests as I am about their enjoyment (p140-2); Centred on vegetables, the set menu features dishes with sparse use of oils and fats and light on the stomach (c30-2)”. “Regional ingredient sourcing” indicates the necessity to foster a deeper understanding and selection of local, seasonal, or organic ingredients, for example “We use mainly ingredients from nearby such as herbs, river fish and mushrooms, thus reducing our food mileage (p6-3); For years the outstanding regional, often organically certified produce has been par for the course here (c97-3)”. “Cooking habits and waste reduction” indicates the imperative need for improving culinary waste issues and promoting resource conservation, for example “We use everything—including stems, skins and shoots—and our leftover cuts are transformed into snacks (p58-2); Their uniforms are made from discarded bed linen (c43-3)”. “Social engagement and cultural awareness” highlights the importance of increased participation in social activities and facilitates the dissemination of traditional culture through food, for example “I like to think that my kitchen is a meeting place, it is the expression of the links I nurture with my producers and my environment (p165-1); The food displays influences of indigenous cultures, featuring native ingredients such as mock betel nut and paper mulberry leaf (c22-4)”.

4.1.2. Discussion

These results provide further insight into the interconnection and advancement of diet and sustainability. Based on the definitions of sustainable diet and emotional design, the five categories are subsequently classified. First, the instinctive level pertains to the product itself, specifically “plant-based food and experiences”. Second, the behavioral level encompasses the interactive health effects stemming from diet, particularly “health and knowledge-based education”. Finally, the reflective level embraces the concept of sustainability, specifically the alignment of “regional ingredient sourcing” with economic sustainability, “cooking habits and waste reduction” bring in environmental sustainability, and “social engagement and cultural awareness” support social sustainability. Further research aims to identify and validate specific factors that can influence food choices.

4.2. Experimental Study-Instinctive-, Behavioral-, and Reflective-Level Experimental Analysis

4.2.1. Study 1-1

Process

Participants for Study 1-1 were recruited via the online experimental platform Credamo (https://www.credamo.com (accessed on 5 April 2024)), a survey platform similar to MTurk, yielding a total of 228 participants (59.6% female, M_age = 30.57, SD = 8.33).

After reading the informed consent and answering the basic demographic questions, participants were asked to indicate their level of hunger on a sliding scale ranging from 0 (full) to 100 (hunger). Then, one of the six groups of experimental materials was randomly selected, and participants were invited to read a textual description about a given picture of a dish. The context reads: ‘Imagine that you are preparing to go out for a meal and are selecting the dish you wish to eat from a restaurant’s website page (without considering price), read the introduction text carefully’, and the introduction text simulates the perception of the dish picture through the five senses. Participants were next prompted to respond to a series of questions rooted in the context, where the question pertaining to choice intention [41] consisted of three items (‘How much would you like to consume the dish depicted in the picture given the textual description of the dish?’, ‘If you were inclined to purchase it, would you be more inclined to consume the dish described in the picture?’, ‘To what extent would you consider consuming the dish in the picture based on its description?’, α = 0.88). Participants were then required to respond to the question regarding perceived attractiveness [42], which comprised three items (‘How attractive is the dish presented to you?’ ‘How tempting is the dish presented to you?’ ‘How enjoyable would it be if you ate the dish presented?’, α = 0.73). Participants were thanked for their time and effort, with monetary compensation provided upon completion of the experiment.

Results

The t-test revealed that all five sensory descriptions of the dish significantly increased choice intention, compared with simply introducing the ingredients that comprise the dish (

Table 1. Results of Study 1-1. The impact of sensory simulation on choice intention and the impact of sensory simulation on perceived attractiveness.

Sensory Simulation	Choice Intention				Perceived Attractiveness
	M	SD	t	p	M	SD	t	p
Control	4.29	1.49	-	-	4.14	1.59	-	-
Visual	5.76	0.60	5.41	<0.05	5.70	0.72	5.27	<0.05
Auditory	5.73	0.69	5.14	<0.05	5.56	0.81	4.95	<0.05
Olfactory	5.65	0.72	6.25	<0.05	5.66	0.86	5.27	<0.05
Gustatory	5.96	0.68	4.76	<0.05	5.97	0.71	6.45	<0.05
Tactile	5.60	0.89	5.60	<0.05	5.60	0.85	5.11	<0.05

). Among them, visual (t(72) = −5.40, p < 0.05, Cohen’s d = 0.28, M_visual = 5.76 > M_control = 4.29), auditory (t(76) = −5.41, p < 0.05, Cohen’s d = 0.27, M_auditory = 5.73 > M_control = 4.29), olfactory (t(77) = −5.14, p < 0.05, Cohen’s d = 0.26, M_olfactory = 5.65 > M_control = 4.29), gustatory (t(75) = −6.25, p < 0.05, Cohen’s d = 0.27, M_gustatory = 5.96 > M_control = 4.29), and tactile (t(78) = −4.76, p < 0.05, Cohen’s d = 0.27, M_tactile = 5.60 > M_control = 4.29). The t-test also revealed that all five sensory descriptions of the dish significantly increased perceived attractiveness. Among them, visual (t(72) = −5.27, p < 0.05, Cohen’s d = 0.30, M_visual = 5.70 > M_control = 4.14), auditory (t(76) = −4.95, p < 0.05, Cohen’s d = 0.29, M_auditory = 5.56 > M_control = 4.14), olfactory (t(77) = −5.27, p < 0.05, Cohen’s d = 0.29, M_olfactory = 5.66 > M_control = 4.14), gustatory (t(75) = −6.45, p < 0.05, Cohen’s d = 0.28, M_gustatory = 5.97 > M_control = 4.14), and tactile (t(78) = −5.11, p < 0.05, Cohen’s d = 0.28, M_tactile = 5.60 > M_control = 4.14).

To test the mediating effect, a bootstrap test was conducted using Process Model 4, with the number of bootstrap samples set at 5000 and the confidence interval set at 95%. PROCESS is an observed variable OLS and logistic regression path analysis modeling tool [43]. Process Model 4 is suitable for analyzing and testing the process in which independent variables affect the dependent variable through mediating variables. Sensory simulation served as the independent variable (0 = control group, 1 = visual, 2 = auditory, 3 = olfactory, 4 = gustatory, 5 = tactile), perceived attractiveness as the mediating variable, choice intention as the dependent variable, and hunger level as the control variable for analysis. The results revealed that the confidence intervals (CIs) of the ‘visual’ group were [0.68, 1.62] the ‘auditory’ group [0.59, 1.52], the ‘olfactory’ group [0.68, 1.62], the ‘gustatory’ group [0.91, 1.87], and the ‘tactile’ group [0.66, 1.55]. The exclusion of 0 from the results indicated the sensory description simulation of dishes enhances choice intention through an increase in perceived attractiveness.

4.2.2. Study 1-2

Process

A total of 427 participants were recruited (61.2% female, M_age = 30.78, SD = 7.85).

Study 1-2 comprised a 6 (control/visual/auditory/olfactory/gustatory/tactile) × 2 (eating alone/eating together) between-groups experiment, randomly allocating participants to one of 12 experimental groups. After reading informed consent and responding to basic information queries, we invited participants to read a textual description of the given pictures of a dish. We randomly introduced a context and invited participants to imagine either ‘preparing to eat alone, selecting the dish you want to eat from a restaurant’s website page (without considering price), read the introduction text carefully’ or ‘preparing to eat with friends’. The introduction text simulates the five senses perception of the dish picture, consistent with the content of Study 1-1. Following this, a series of questions were answered based on the given situations, including those related to choice intention and perceived attractiveness. Participants were thanked for their participation and compensated with cash at the end of the experiment.

Results

Through a multifactorial ANOVA test, how eating alone or eating together affected the relationship between sensory simulation and perceived attractiveness was analyzed (

Table 2. Results of Study 1-2. The impact of eating alone and eating together on perceived attractiveness.

Sensory Simulation	Perceived Attractiveness				F	η2
	Eating Alone		Eating Together
	M	SD	M	SD
Control	4.76	0.21	4.30	0.19	2.61	0.006
Visual	5.04	0.18	5.46	0.18	2.87	0.007
Auditory	5.71	0.17	5.51	0.17	0.69	0.002
Olfactory	5.91	0.18	5.49	0.17	2.99	0.007
Gustatory	5.47	0.17	5.91	0.18	3.16	0.008
Tactile	5.98	0.17	5.57	0.18	2.85	0.007

). A between-subjects effects test demonstrated a significant moderating effect (F(5, 421) = 2.86, p < 0.1, η² = 0.003). Next, simple effects analyses were conducted for each group. The results indicated that in the ‘visual’ group (F(1, 415) = 2.87, p < 0.1, η² = 0.007) and the ‘gustatory’ group (F(1, 415) = 3.16, p < 0.1, η² = 0.008), the perceived attractiveness of eating together was greater than eating alone. In the ‘olfactory’ group (F(1, 415) = 2.99, p < 0.1, η² = 0.007) and the ‘tactile’ group (F(1, 415) = 2.85, p < 0.1, η² = 0.007), the perceived attractiveness of eating alone was greater than eating together.

To test the moderated mediating effect, a bootstrap test was conducted using Process Model 7, with a sample size of 5000 and a confidence interval of 95%. Process Model 7 is suitable for analyzing and testing the process by which moderating variables affect the relationship between independent and mediating variables, thereby influencing the dependent variable [43]. Sensory simulation served as the independent variable, perceived attractiveness as the mediating variable, choice intention as the dependent variable, eating alone or eating together as the moderating variable (1 = eating alone, 2 = eating together), and hunger level as the control variable for the analyses. The results indicated that the CIs were positive in the ‘visual’ group [0.03, 1.77] and the ‘gustatory’ group [0.03, 1.76]. The CIs were negative in both the ‘olfactory’ group [−1.50, −0.24] and the ‘tactile’ group [−1.51, −0.24], excluding 0. The result in the ‘auditory’ group [−1.27, 0.01], including 0, indicated the invalidity of the moderated mediation effect.

4.2.3. Study 1-3

Process

Participants for Study 1-3 were recruited via Credamo, excluding those who had participated in Studies 1-1 and 1-2. A total of 448 participants were recruited (58.3% female, M_age = 31.17, SD = 8.45). Study 1-3 comprised a 6 (control/visual/auditory/olfactory/gustatory/tactile) × 2 (self-representation/other-representation) between-groups experiment, wherein participants were randomly allocated to one of the 12 experimental groups. We randomly introduced a context and invited participants to imagine ‘preparing to go out for a meal and selecting the dish you want to eat from a restaurant’s website page (without considering price)’. Participants were required to simulate the five senses of perception that they or others could experience, while the remaining processes remained identical to Study 1-1.

Results

A between-subjects effects test demonstrated a significant moderated effect (F(5, 436) = 4.75, p < 0.1, η² = 0.052). Subsequently, simple effects analyses were conducted for each group. The results indicated that in the ‘visual’ group (F(1, 436) = 5.02, p < 0.1, η² = 0.011) and the ‘gustatory’ group (F(1, 436) = 3.57, p < 0.1, η² = 0.008), the perceived attractiveness of other representation was greater than that of self-representation. In the ‘auditory’ group (F(1, 436) = 3.28, p < 0.1, η² = 0.007), the ‘olfactory’ group (F(1, 436) = 3.96, p < 0.1, η² = 0.009), and the ‘tactile’ group (F(1, 436) = 6.20, p < 0.1, η² = 0.014), the perceived attractiveness of self-representation was greater than other-representation (

Table 3. Results of Study 1-3. The impact of self-representation and other-representation on perceived attractiveness.

Sensory Simulation	Perceived Attractiveness				F	η2
	Self-Representation		Other-Representation
	M	SD	M	SD
Control	4.98	0.177	4.41	0.175	5.19	0.012
Visual	5.43	0.168	5.97	0.177	5.02	0.011
Auditory	5.96	0.175	5.53	0.168	3.28	0.007
Olfactory	5.84	0.175	5.34	0.177	3.96	0.009
Gustatory	5.44	0.177	5.92	0.185	3.57	0.008
Tactile	6.03	0.168	5.44	0.168	6.20	0.014

).

To test the moderated mediating effect, a bootstrap test was conducted using Process Model 7, with a sample size of 5000 and a confidence interval of 95%. Sensory simulation served as the independent variable, perceived attractiveness as the mediating variable, choice intention as the dependent variable, self-with-other representation as the moderating variable (1 = self-representation, 2 = other-representation), and hunger level as the control variable for analysis. The results indicated that the CIs were positive in the ‘visual’ group [0.31, 1.93] and the ‘gustatory’ group [0.20, 1.86]. The CIs were negative in the ‘auditory’ group [−1.56, −0.41], the ‘olfactory’ group [−1.63, −0.46], and the ‘tactile’ group [−1.70, −0.57], with none of the results encompassing 0.

4.2.4. Study 1-4

Process

Participants for Study 1-4 were recruited via Credamo and excluded participants in Studies 1-1, 1-2, and 1-3. A total of 810 participants were recruited (61.6% female, Mage = 30.34, SD = 8.24). Study 1-4 comprised a 6 (control/visual/auditory/olfactory/gustatory/tactile) × 2 (eating alone/eating together) × 2 (self-representation/other-representation) between-groups experiment, randomly assigning participants to one of the 24 experimental groups. Randomly introduced contexts in which participants were invited to imagine eating alone or eat together, as well as the experiential perspectives involving the five senses: ‘preparing to eat alone’ and ‘I can experience’; ‘preparing to eat with friends’ and ‘I can experience’; ‘preparing to eat alone’ and ‘others can experience’; ‘preparing to eat with friends’ and ‘others can experience’. The remainder of the procedure was consistent with Study 1-1.

Results

To investigate the co-moderated mediation effect, a bootstrap test was conducted using Process Model 9, with sensory simulation as the independent variable, perceived attractiveness as the mediating variable, choice intention as the dependent variable, eating alone or eating together as the moderating variable 1, self-with-other representation as the moderating variable 2, and hunger level as the control variable for analysis. Process Model 9 is suitable for analyzing and testing the process in which both moderator variable 1 and moderator variable 2 simultaneously affect the relationship between independent and mediating variables, thereby influencing the dependent variable [43]. The results revealed significant effects for both the moderating variable 1 (R² = 0.02, F(5, 791) = 4.33, p < 0.001) and moderating variable 2 (R² = 0.03, F(5, 791) = 6.05, p < 0.001). The confidence intervals (CIs) for eating alone showed positive results for the ‘visual’ group [0.17, 1.29] and the ‘gustatory’ group [0.24, 1.36]; negative results for the ‘olfactory’ group [−1.18, −0.29] and the ‘tactile’ group [−1.10, −0.20], while the ‘auditory’ group showed [−0.94, 0.04]. The confidence intervals (CIs) for self-with-other representation indicated that the ‘visual’ group [0.32, 1.43] and the ‘gustatory’ group were positive [0.17, 1.29], and the ‘auditory’ group [−1.41, −0.52], the ‘olfactory’ group [−1.42, −0.53], and the ‘tactile’ group were negative [−1.26, −0.36].

4.2.5. Study 2-1

Process

Participants for Study 2-1 were recruited via Credamo, yielding a total of 173 participants (66.5% female, M_age = 31.29, SD = 8.03).

The experiment first invites participants to answer some demographic questions, including gender, age, height, weight, dietary habits, and hunger levels. Subsequently, participants are invited to engage in a simulation scenario involving a control group and the selection of food components for four distinction categories. Thereafter, participants are prompted to respond to a sequence of inquiries, encompassing their choice intentions and health perceptions. The measurement of choice intention (α = 0.89) is the same as in study 1-1. The reference framework for measuring health perception [44] comprises the subsequent questions: “If I choose this sandwich, it will make me feel more energetic”, “improve my health”, “reduce my risk of health problems”, “give me more nutrition”, and “benefit me” (α = 0.90).

Results

According to t-test analysis, compared with the control group, carbohydrate (t(70) = −4.05, p < 0.05, Cohen’s d = 0.28, M_carbohydrate = 5.73 > M_control = 4.59), protein (t(72) = −3.87, p < 0.05, Cohen’s d = 0.28, M_protein = 5.67 > M_control = 4.59), dietary fiber (t(65) = −2.23, p < 0.05, Cohen’s d = 0.34, M_{dietary fiber} = 5.34 > M_control = 4.59), and fat (t(69) = −3.32, p < 0.05, Cohen’s d = 0.28, M_fat = 5.54 > M_control = 4.59) will significantly increase the choice intention. In addition, compared with the control group, the carbohydrate (t(70) = −6.66, p < 0.05, Cohen’s d = 0.25, M_carbohydrate = 5.96 > M_control = 4.26), protein (t(72) = −6.11, p < 0.05, Cohen’s d = 0.24, M_protein = 5.76 > M_control = 4.26), dietary fiber (t(65) = −3.26, p < 0.05, Cohen’s d = 0.32, M_{dietary fiber} = 5.31 > M_control = 4.26), and fat (t(69) = −4.94, p < 0.05, Cohen’s d = 0.27, M_fat = 5.57 > M_control = 4.26) will enhance health perception (

Table 4. Results of Study 2-1. The impact of nutrition on choice intention and the impact of nutrition on health perception.

Nutrition	Choice Intention				Health Perception
	M	SD	t	p	M	SD	t	p
Control	4.59	1.45	-	-	4.26	1.34	-	-
Carbohydrate	5.73	0.85	4.05	<0.05	5.96	0.71	5.96	<0.05
Protein	5.67	0.86	3.87	<0.05	5.76	0.65	5.76	<0.05
Dietary fiber	5.34	0.87	2.23	<0.05	5.31	0.67	3.26	<0.05
Fat	5.54	0.85	3.32	<0.05	5.57	0.81	4.94	<0.05

).

To test the mediating effect, a bootstrap test was conducted using Process Model 4, with the number of bootstrap samples set at 5000 and the confidence interval set at 95%. The results of each nutritional element showed that the carbohydrate group (95% CI [0.27, 1.34]), protein group (95% CI [0.57, 1.57]), dietary fiber group (95% CI [0.68, 1.70]), and fat group (95% CI [0.44, 1.46]) did not include 0.

4.2.6. Study 2-2

Process

Participants for Study 2-2 were recruited via Credamo and excluded participants in Study 2-1. A total of 350 participants were recruited (68.6% female, M_age = 30.99, SD = 7.98). Study 2-2 comprised a 5 (control/carbohydrate/protein/dietary fiber/fat) × 2 (process/outcome) between-groups experiment, randomly assigning participants to one of the 10 experimental groups. Participants were required to simulate a scenario that includes selecting food ingredients corresponding to the same nutrients as Study 2-1. In addition, descriptions of the process or outcome of nutrients on the body have been added. Then, participants were invited to answer questions about health perception (α = 0.85) and choice intention (α = 0.83), with the same measurement as in study 2-1.

Results

The results indicated a significant interaction effect between mental simulation and food ingredient replacement (F(4, 340) = 2.38, p < 0.1, η² = 0.030), whereby the influence of result simulation on health perception surpassed that of process simulation. The results of the control group were not significant (F(1, 340) = 2.34, p > 0.1, η² = 0.001). The results of each experimental group were significant, the carbohydrate group (F(1, 340) = 4.17, p < 0.1, η² = 0.013), protein group (F(1, 340) = 2.84, p < 0.1, η² = 0.010), dietary fiber group (F(1, 340) = 2.78, p < 0.1, η² = 0.012), and fat group (F(1, 340) = 3.76, p < 0.1, η² = 0.011) among the experimental groups (

Table 5. Results of Study 2-2. The impact of process and outcome on health perception.

Nutrition	Health Perception				F	η2
	Process		Outcome
	M	SD	M	SD
Control	4.82	1.09	4.53	0.83	2.34	0.001
Carbohydrate	5.56	0.98	5.96	0.46	4.17	0.013
Protein	5.62	0.70	5.93	0.55	2.84	0.010
Dietary fiber	5.45	0.64	5.81	0.77	2.78	0.012
Fat	5.58	0.78	5.94	0.51	3.76	0.011

).

To test the moderated mediating effect, a bootstrap test was conducted using Process Model 7, with a sample size of 5000 and a confidence interval of 95%. The results of each nutritional element showed that the carbohydrate group (95% CI [0.14, 1.16]), protein group (95% CI [0.09, 1.15]), dietary fiber group (95% CI [0.16, 1.22]), and fat group (95% CI [0.13, 1.19]) did not include 0.

4.2.7. Study 2-3

Process

Participants for Study 2-3 were recruited via Credamo and excluded participants in Studies 2-1 and 2-2. A total of 315 participants were recruited (68.3% female, M_age = 30.89, SD = 8.34). Study 2-3 comprised a 5 (control/carbohydrate/protein/dietary fiber/fat) × 2 (benefit/harm) between-groups experiment, randomly assigning participants to one of the 10 experimental groups. Participants were required to simulate a scenario that includes selecting food ingredients corresponding to the same nutrients as Study 1-1. In addition, referring to Ahn [45], the benefit description introduces the benefits that ingredients can bring to the body, while the harm description introduces the reduction of negative effects on the body. Then, participants were invited to answer questions about health perception (α = 0.84) and choice intention (α = 0.85), with the same measurement as in study 2-1.

Results

The results indicated a significant interaction effect between regulatory focus and food ingredient replacement (F(4, 305) = 3.55, p < 0.1, η² = 0.040), whereby the influence of benefit simulation on health perception surpassed that of harm simulation. The results of the control group were not significant (F(1, 305) = 2.48, p > 0.1, η² = 0.001). The results of each experimental group were significant: the carbohydrate group (F(1, 305) = 3.58, p < 0.1, η² = 0.010), protein group (F(1, 305) = 3.10, p < 0.1, η² = 0.010), dietary fiber group (F(1, 305) = 6.16, p < 0.1, η² = 0.020), and fat group (F(1, 340) = 3.60, p < 0.1, η² = 0.040) among the experimental groups (

Table 6. Results of Study 2-3. The impact of benefit and harm on health perception.

Nutrition	Health Perception				F	η2
	Benefit		Harm
	M	SD	M	SD
Control	4.68	1.03	5.03	0.94	2.48	0.001
Carbohydrate	5.89	0.61	5.41	0.85	3.58	0.010
Protein	6.02	0.45	5.64	1.04	3.10	0.010
Dietary fiber	5.84	0.53	5.45	0.98	6.16	0.020
Fat	6.02	0.48	5.29	1.09	3.60	0.040

).

To test the moderated mediating effect, a bootstrap test was conducted using Process Model 7, with a sample size of 5000 and a confidence interval of 95%. The results of each nutritional element showed that the carbohydrate group (95% CI [−1.36, −0.16]), protein group (95% CI [−1.37, −0.15]), dietary fiber group (95% CI [−1.38, −0.21]), and fat group (95% CI [−1.66, −0.48]) did not include 0.

4.2.8. Study 2-4

Process

Participants for Study 2-4 were recruited via Credamo, and excluded participants in Studies 2-1, 2-2, and 2-3. A total of 680 participants were recruited (66.9% female, M_age = 30.68, SD = 7.98). Study 2-4 comprised a 5 (control/carbohydrate/protein/dietary fiber/fat) × 2 (process/outcome) × 2 (benefit/harm) between-groups experiment, randomly assigning participants to one of the 20 experimental groups. Participants were required to simulate a scenario that includes selecting food ingredients corresponding to the same nutrients as Study 2-1. The remainder of the procedure was consistent with Study 2-1, including answering the question about health perception (α = 0.86) and choice intention (α = 0.84).

Results

To investigate the co-moderated mediation effect, a bootstrap test was conducted using Process Model 9, with nutrition as the independent variable, health perception as the mediating variable, choice intention as the dependent variable, mental simulation as the moderating variable 1, and regulatory focus as the moderating variable 2. The results of each nutritional element showed that the carbohydrate group (95%CI₁ [0.29, 1.08]; 95%CI₂ [−0.91, −0.13]), protein group (95%CI₁ [0.20, 0.98]; 95%CI₂ [−0.90, −0.13]), dietary fiber group (95%CI₁ [0.26, 1.04]; 95%CI₂ [−0.94, −0.15]), and fat group (95%CI₁ [0.24, 1.02]; 95%CI₂ [−0.88, −0.11]) did not include 0.

4.2.9. Study 3-1

Process

Participants for Study 3-1 were recruited via Credamo and a total of 680 participants were recruited (62.3% female, M_age = 31.18, SD = 8.87). After reading the informed consent, participants initially responded to general demographic questions including gender, age, education, occupation, prior concerns regarding sustainability, and hunger levels. Subsequently, participants were randomly allocated to one of four experimental contexts (control group/economic/social/environmental) and were prompted to imagine the scenario of preparing to dine out and selecting the dish from a restaurant’s website, together with a picture of a plant-based dish. Following this, participants responded to a series of questions pertaining to choice intention (α = 0.86), questions assessing senses of self-worth (α = 0.93), and a statement, ‘Choosing this dish makes me feel that: it would contribute to addressing sustainability-related issues, create new opportunities for addressing sustainability issues, enhance sustainable development processes, boost sustainable development practices, help to achieve sustainable development goals, and the benefits to sustainable development make me feel more responsible’ [46]. Participants were thanked for their time contribution with a cash reward upon completion of the experiment.

Results

According to t-test analysis, compared with the control group, economic (t(72) = −2.65, p < 0.05, Cohen’s d = 0.26, M_economic = 5.73 > M_control = 4.97), social (t(72) = −2.35, p < 0.05, Cohen’s d = 0.28, M_social = 5.63 > M_control = 4.97), and environment (t(72) = −2.87, p < 0.05, Cohen’s d = 0.26, M_environment = 5.72 > M_control = 4.97) will significantly increase the choice intention. In addition, compared with the control group, the economic (t(72) = −5.86, p < 0.05, Cohen’s d = 0.25, M_economic = 5.73 > M_control = 4.28), social (t(72) = −2.35, p < 0.05, Cohen’s d = 0.29, M_social = 5.25 > M_control = 4.28), and environment (t(72) = −4.73, p < 0.05, Cohen’s d = 0.27, M_environment = 5.57 > M_control = 4.28) will enhance sense of self-worth (

Table 7. Results of Study 3-1. The impact of context on choice intention and the impact of context on sense of self-worth.

Context	Choice Intention				Sense of Self-Worth
	M	SD	t	p	M	SD	t	p
Control	4.97	1.42	-	-	4.28	1.42	-	-
Economic	5.73	0.64	2.65	<0.05	5.86	0.73	5.86	<0.05
Social	5.63	0.90	2.35	<0.05	5.73	0.95	2.35	<0.05
Environment	5.72	0.87	2.87	<0.05	4.73	0.74	4.73	<0.05

).

To test the mediating effect, a bootstrap test was conducted using Process Model 4, with the number of bootstrap samples set at 5000 and the confidence interval set at 95%. The results of each element showed that the economic group (95% CI [0.31, 1.08]), social group (95% CI [0.15, 0.90]), and environment group (95% CI [0.48, 1.23]) did not include 0.

4.2.10. Study 3-2

Process

Participants for Study 3-2 were recruited via Credamo and excluded participants in Studies 3-1. A total of 292 participants were recruited (53.7% female, M_age = 32.50, SD = 9.20). Study 3-2 comprised a 4 (control/economic/social/environment) × 2 (step-by-step/all-at-once) between-groups experiment, randomly assigning participants to one of the eight experimental groups. Participants were required to simulate a scenario that includes selecting food ingredients corresponding to the same nutrients as Study 3-1. The textual descriptions forms drew from Wu [47] and manipulated into either four-step or whole paragraphs. The step-by-step description underscores the causal relationship between paragraphs, utilizing transitional phrases such as “First”, “Second”, “Next”, and “Finally”. Then, participants were invited to answer questions about health perception (α = 0.83) and choice intention (α = 0.93), with the same measurement as in study 3-1.

Results

The results revealed a significant interaction effect between sustainable descriptions and textual form (F(3, 284) = 2.46, p < 0.1), η² = 0.003). Step-by-step descriptions (M_step-by-step = 16.20, SD = 1.08) were more likely to enhance the sense of self-worth compared to all-at-once descriptions (M_all-at-once = 5.80, SD = 0.65). In the control group, the results were not significant (F(1, 284) = 2.45, p > 0.1, η² = 0.009). In the experimental group, the results for the economic (F(1, 284) = 2.87, p < 0.1, η² = 0.010), social (F(1, 284) = 2.76, p < 0.1, η² = 0.010), and environmental results (F(1, 284) = 2.80, p < 0.1, η² = 0.010) were significant (

Table 8. Results of Study 3-2. The impact of step-by-step descriptions and all-at-once descriptions on sense of self-worth.

Context	Sense of Self-Worth				F	η2
	Step-by-Step		All-at-Once
	M	SD	M	SD
Control	4.00	1.47	4.42	1.41	2.46	0.009
Economic	5.87	0.58	5.47	1.17	2.87	0.010
Social	5.57	0.78	5.18	1.25	2.76	0.010
Environment	5.96	0.57	5.55	0.83	2.80	0.010

).

To test the moderated mediating effect, a bootstrap test was conducted using Process Model 7, with a sample size of 5000 and a confidence interval of 95%. The results of each element showed that the economic group (95% CI [−1.52, −1.03]), social group (95% CI [−1.52, −0.15]), and environment group (95% CI [−1.58, −0.18]) did not include 0.

4.2.11. Study 3-3

Process

Participants for Study 3-3 were recruited via Credamo and excluded participants in Studies 3-1 and 3-2. A total of 571 participants were recruited (66.2% female, M_age = 31.11, SD = 8.62). Study 3-3 comprised a 4 (control/economic/social/environment) × 2 (step-by-step/all-at-once) × 2 (photo/painting) between-groups experiment, randomly assigning participants to one of the 16 experimental groups. Participants were prompted to imagine that they were preparing to dine out and selecting the dish on a restaurant’s website, alongside a picture of a plant-based dish. The experimental materials and textual descriptions pertaining to the basic instructions of dishes remained consistent with those utilized in Study 3-2. Photos were searched based on textual descriptions, and artists were commissioned to render the photographs in a painting format for picture manipulation purposes. The measurement of choice intention (α = 0.87) and sense of self-worth (α = 0.91) remained consistent with those in Study 3-1.

Results

To test the moderated mediation effect, a bootstrap test of PROCESS model 11 was conducted with a sample size of 5000 and a confidence interval of 95%. Process Model 11 is applicable for analyzing and testing the impact of moderator variable 2 on moderator variable 1 in influencing the relationship between independent and mediating variables, thereby affecting the process of the dependent variable [43]. Sustainability descriptions as the independent variable, textual and pictorial forms as moderating variables, sense of self-worth as the mediator, and choice intention as the dependent variable. The results showed that the mediation effect was established (95% CI [0.09, 0.38]). In addition, the mediating effect of “sustainable description → self-worth → choice intention” holds true under the condition of photo form (95% CI [0.11, 0.35]) and also holds true under the condition of painting form (95% CI [0.09, 0.31]).

4.2.12. Discussion

The experimental results at the instinctive level indicate that mental simulations of the five senses enhance choice intention. Moreover, influenced by eating together and the visual and gustatory perceptions of others, and simulations of personal olfactory and tactile perceptions further enhance choice intention. Individuals’ auditory perception can likewise motivate choice intention. The behavioral-level experimental results reveal that providing healthier choices aligned with nutritional elements boosts choice intention, particularly when emphasizing the positive outcomes of replacement, thereby achieving the highest impact on health perception. The experimental results of the reflective level indicated that incorporating a sustainable background explanation encompassing the economy, environment, and society augments choice intention for plant-based dishes through sense of self-worth, and a step-by-step introduction and accompanying photos are optimal for providing authenticity.

The factors influencing food selection as well as the conditions under which these factors can maximize their value have been identified through experiments. Consequently, the validated and effective influencing factors will serve as the themes of the cards, while the conditions necessary for achieving the optimal solution will be incorporated into the explanatory content for the prototype design of the card set.

4.3. Prototype Conception—Emotional Design Card Themes

4.3.1. Results

Eighteen cards were designed, comprising five theme cards corresponding to three parts, with a catalog card for each part. The first part, titled “product”, explores how increasing attention to sensory perception of plant-based foods can enhance the dietary experience, including ‘visual experience’, ‘auditory experience’, ‘olfactory experience’, ‘taste experience’, and ‘tactile experience’. The second part, “promotion”, delves into the impact on health and knowledge-based educational behaviors, comprising five themes: ‘dietary fiber’, ‘protein’, ‘carbohydrates’, ‘fats’, and ‘health’. The third part, “profit”, explores the profound connection between diet and sustainability: ‘regional food sources’, ‘social participation and cultural awareness’, ‘cooking habits and waste management’, ‘sustainable information utilization’, and ‘food safety precautions’. The front (recto) of each theme card features the theme name, logo, inspirational questions, and category, while the reverse side (verso) comprises question prompts, usage suggestions, and the corresponding category (as shown in Figure 3).

4.3.2. Discussion

A prototype of the card set was generated, and the findings from the case analysis and experimental study were thoroughly utilized. The independent variables in the experiment serve as the “theme name”, the manipulations act as the “keywords” for the “question”, and the mental simulation effect mechanism results constitute the “answer” to the “question”. Further research is required to assess the utility and identify avenues for the improvement of the cards in targeted problem-solving contexts.

4.4. User Testing—Card Application Testing and Improvement

4.4.1. Results

The results indicated that each card stimulated the interest and attention of participants to varying degrees, with 76.9% of participants paying greater attention to the “product” category, aiming to comprehensively enhance the sensory utilization of the food itself at the instinctive level. Participants remarked that “the cards can increase my innate interest in plant-based foods, make me more willing to eat vegetables, and want to share these feelings with my family”. As to whether the card enhances existing meals, greater attention was given to the “promotion” category, comprising 61.5% of the participations, with the majority of those opting for improvement believing that health and nutrition should be prioritized at the behavioral level: participants remarked that “the health and other information pertaining to food is well presented, showing aspects that we usually overlook”, while a minority believed that it could enhance the sensory experience. Participants who did not opt for improvement argued that they had already achieved nutritional balance. For the novel food-related knowledge provided by the cards, 69.2% of the participants asserted that the “profit” category imparted greater insight at the reflective level, particularly in its implications for society and the economy: participants mentioned that they gained “a fresh perspective on the relationship between sustainability and food, I had previously overlooked the influence of food sources on the local market, yet I now perceive that food culture exerts a profound impact on society, and the specialties in each locale vary”. Expectations for future food design encompassed greater diversity in food presentation, enhanced nutrition, and greater environmental friendliness. The impact on food choices in the next week comprised a more nuanced understanding of the food itself at the instinctive level (“utilizing the freshest ingredients to accentuate the natural sweetness”), advancements in health at the behavioral level (“selecting organic foods that promote bodily wellness”), and aspirations for sustainable food sources at the reflective level (“prioritizing locally grown, seasonal foods wherever possible in the next week”).

4.4.2. Discussion

The results indicate that each theme of the cards stimulated the participants’ understanding and imagination of sustainable diet in various ways. To a certain extent, the cards facilitated modifications in participants’ diet plans, which has the potential to influence both immediate decisions, such as altering the current meal (“the dishes initially appeared mundane, yet subsequent to the change, I enriched the color palette”; “before the change, I didn’t pay attention to auditory sensations, but after the change, I increased the crunchiness of the food”; “the majority of dishes consisted of meat, yet subsequent to the change, I incorporated vegetables and fruits, thereby enhancing the nutritional value”; “I frequently left the faucet running during cooking, yet subsequent to the change, I became mindful of conserving water usage”), and future ones, such as meal planning for the next week (“enhance consideration of diverse nutritional facets and derive greater enjoyment from food through visual, auditory, and other sensory modalities”; “attend to food storage techniques and cultural contexts”; “promote nutritional diversity, with a preference for plant-based protein sources”). However, there remained several issues, such as the ambiguous comprehension of the correlation between sustainability and diet (e.g., the misconception that economic and social sustainability are unconnected to dietary practices), as well as the unclear manner of utilizing the cards (e.g., unclear associations between catalog cards and theme cards). The next step entailed refining the design of these elements.

4.5. Card Set—Sustainable Diet 3P Emotional Design Method

Several participants indicated their unfamiliarity with the definition of sustainability, asserting that the connection with sustainability beyond environmental protection was comparatively minor and thus affirming a prior ambiguous interpretation of the sustainable diet concept [13]. After further conceptual clarification, participants came to understand that the concept of sustainability can be broadened to encompass the entire food system [37], and intangible cultural heritage, such as food preparation techniques, is intricately linked to daily food consumption, constituting a crucial aspect of social sustainability. Following the explanation, the participants gained a deeper understanding and recognition of the concept of a plant-based sustainable diet, and argued that the card should incorporate an introductory section on the sustainable diet concept as well as a distinct introduction to the card’s utilization.

In addition to making modifications to address this content, the final version has undergone a more rigorous format review, refining any awkward or unclear statements. The final card set comprises 20 cards, encompassing a cover card (the front is “Plant-based Sustainable Diet 3P Emotional Design Method”; the reverse is the purpose of the card design), a definition card (the front is “Instructions for Use”; the reverse introduces the definition, the three levels of emotional design, and how to use the card), and 3 catalog cards (the front is the category logo and name; the reverse is the category theme logo, keywords, and inspirational questions, as shown in Figure 4), as well as 15 theme cards. The enhanced cards have been recognized and familiarized to all users tested, and everyone expressed a desire to utilize the card set for longer-term sustainable diet plans.

5. General Discussion

Adopting a plant-based sustainable diet can yield benefits to individuals, including health improvements, and to the planet, such as supporting sustainable development. Therefore, promoting plant-based sustainable diets is deemed an integral component in supporting future development. Emotional design harnesses the influence of psychological emotions, enabling individuals to make spontaneous product decisions, and it can also be employed to promote plant-based sustainable diet choices. Card sets, as potential design tools for concept generation, have demonstrated their efficacy in addressing a range of issues. Based on the conditions outlined above, this study developed a “Plant-based Sustainable Diet 3P Emotional Design Method” card set that enables individuals to design their own sustainable diet plans. During the card design process, we conducted experimental research into the mechanisms influencing food choices and designed the card content accordingly, and this was validated through iterative user testing in facilitating novel food-related awareness.

Based on the experimental conclusion at the instinctive level in the second step of card set development, perceptual simulation of the five senses in plant-based dishes can enhance choice intention, which is influenced by varying the numbers of diners and diversity in dining perspectives. Drawing from the conclusion, we pose the following thematic questions in the third step: How can plant-based foods be visually harmonized? What auditory experiences do they afford? What advantages does plant aroma offer? How might we amplify the taste? And what tactile engagements arise? During the user test in the fourth step, participants expressed keen interest in this content, aiming to refine their dietary design with the aid of prompts and to encounter novel sensory representations of dishes during dining experiences.

Given the behavioral-level experimental conclusion in the second step of card set development, the selection of healthier ingredients that correspond to nutritional elements impacts health perception. Explaining the outcomes that offer benefits has the most significant impact. Therefore, we have structured the content pertaining to key nutritional elements, highlighting the significance of health in the third step. The provocative questions for designing a prototype of the card set include: How do we optimize the retention of protein nutrition? How can we augment the proportion of dietary fiber in a meal? Which unseen healthy fats can be harnessed? What are the more prevalent sources of carbohydrates? What factors dictate whether a meal is deemed healthy? During user iteration testing in the fourth step, it was observed that some participants had already been equipped to give adequate consideration to health and nutrition, but a significant proportion of participants had indeed neglected health factors and expressed a desire to experiment with healthier choices in the future.

The analysis of the reflective-level experiment in the second step of card set development revealed that the integration of sustainable food-related content exerts a significant influence on sense of self-worth. Considering the inclusion of photos for illustrative purposes in the step-by-step description is crucial, as it constitutes the optimal combination that influences choice intention. In the third step of the card prototype design, the card content poses the following questions: What benefits accrue from selecting regional ingredients? How are food, society, and culture interconnected? How can cooking mitigate its environmental impact? How can sustainable information be harnessed to foster novel experiences? What are the potential food safety concerns in daily life? In subsequent trials in the fourth step, some users responded that their initial comprehension of sustainability contrasted with the novel concept, acknowledging the wider-reaching implications of food, and they expressed a desire to acquire further knowledge pertaining to sustainability.

This study contributes to the literature on sustainable development and sustainable diet through a multidimensional analysis of emotional design. The research innovatively integrates emotional design with sustainable diet research. Previous studies have explored the application and impact of emotional design on food packaging [8], as well as analyzing the design elements that appeal in relation to the food itself, such as enhancing the selection of plant-based foods through aesthetics [18]. However, there is a lack of systematic analysis of the use of affective design for promoting plant-based sustainable diets. The findings of this study demonstrate the effectiveness of integrating the two and have resulted in the development of a design card set. The study uncovered the underlying psychological mechanisms that influence food choice. It analyzed the factors that influence the final decision-making process at the instinctive, behavioral, and reflective levels, and further delved into previous discussions regarding the impact of visual factors on psychological changes under various conditions [48]. It identified pertinent psychological impact mechanisms, encompassing the sensory perception of food, nutrition, and health, as well as economic, environmental, and social sustainability factors. The study provides design approaches for individuals to transition towards a healthier and more sustainable lifestyle. At the instinctive level, methods have been proposed to enhance the sensory experience of plant-based foods. At the behavioral level, it is recommended to consider the impact of diet on health and acquire further nutrition-related knowledge. The reflective level points out the profound connection between diet and sustainability, facilitating the development of plant-based sustainable dietary plans for individuals through the rational utilization of sustainable knowledge. The user test results of the card set affirm that sustainable diets can be propelled by emotional design. It is also crucial to exercise judicious utilization of attention cues across diverse emotional planes while acknowledging the paramount importance of exploring the psychological underpinnings and influential variables that shape dietary decisions.

Furthermore, there are also some limitations to the research. Firstly, the content derived from the card set exhibits a limited scope in addressing economic, social, and environmental sustainability, as each section encompasses diverse yet narrowly focused aspects. In this study, only aspects related to the plant-based sustainable diets were considered. Future research could enhance the integration of sustainability with various aspects and delve deeper into social-level content. Secondly, the focus on the instinctive, behavioral, and reflective levels is relatively limited, and this study only considers the individual effects of each factor. Future research could explore the inclusion of additional emotional elements and undertake a more thorough analysis of the combined impacts of diverse factors. Finally, the influence of the card set on the formulation and modification of long-term dietary habits necessitates empirical validation. Future research can conduct longer-term tracking surveys on an annual basis.

6. Conclusions

Heightened awareness of the nexus between food and sustainability serves as a cost-effective strategy to promote sustainable development. This study developed an emotional design card set aimed at promoting plant-based sustainable diet to support future development through a five-step process: case analysis, experimental study, prototype conception, user testing, and improved design. The results indicate that the card set has had an impact on enhancing awareness of the connection between food and sustainability, enabling individuals to make immediate dietary decisions, to plan for future dietary choices, and to shape longer-term food design expectations. Furthermore, the card set can facilitate individuals in generating their own personalized plant-based sustainable diet plans, encompassing the enhancement of sensory appreciation for plant-based foods at the instinctive level, fostering greater engagement with the health implications of food choices at the behavioral level, and promoting a broadened perspective, alongside habit modifications, pertaining to economic, social, and environmental sustainability at the reflective level.