Design for Well-Being and Sustainability: A Conceptual Framework of the Peer-to-Peer Sharing and Reuse Platform in the Circular Economy

: To regain overall well-being in the post-pandemic era, the priorities should not be only economic growth but also human physical and mental health. This study investigates how to incorporate the concept of well-being into the circular economy to facilitate the pursuit of individual/personal and social growth, and sustainable consumption. We begin with a systematic search of the literature on well-being and sustainable product–service systems, model the well-being components in peer-to-peer (P2P) sharing and reuse platforms, and propose design guidelines for platform development. According to our ﬁndings, (1) allocentric well-being components (such as gratitude, contribution, and altruism) serve as the antecedents of sharing behaviors, while egocentric components (such as pleasure and attachment) serve as the consequences, and (2) information sharing is crucial to initiating the ﬂow of well-being perceptions and sustainable sharing and reuse behaviors. Based on the ﬁndings, we suggest a data-driven approach and active inference theory to facilitate related studies. This study sheds light on the potential to develop well-being within the circular economy and facilitate the sustainable working of the sharing and reuse ecosystem.


Introduction
The Coronavirus disease 2019 (COVID-19) has led to a global crisis against human well-being and has posed a serious threat not only to human physical health but also to mental health. Social isolation normalizes lives centering around online purchases and working from home. The increase in online shopping and postponing of waste recycling increases landfill and environmental pollution [1]. To regain the quality of life in the post-pandemic era, we should pay attention not only to economic growth but also to well-being and sustainability [2][3][4]. During the lockdown, people increased their use of technology to maintain social interaction [5]. However, the more people rely on the Internet, the more difficult it is to improve their well-being and concerns for the environment, which negatively affects psychosocial development [6]. Thus, it is necessary to investigate how human well-being can be sustained without depleting the environment in the postpandemic period and in the future. Since well-being encompasses personal, social, and environmental perspectives that affect the human quality of life, we should consider our economic activities from a global perspective.
Among the potential solutions to this challenge are giving attention to the sustainable product-service system (PSS), where people have novel patterns of consumption and interaction, and providing great potential to develop social and environmental well-being [7][8][9]. For a sustainable PSS, the sharing economy (or collaborative consumption) and circular economy also need to be considered. Although all of their definitions are broad and their clarifications are beyond the scope of this article, we suggest that the circular economy in Google Scholar; (2) collecting the most relevant publications (4900 studies in total) and deleting the duplications of two datasets, leading to around 300 to 600 publications for each component; (3) eliminating the book, book chapter, non-English text, and unavailable full texts, leading to a decrease in the total number of publications to 617 (for each of the components there are 46,64,107,62,104,45,57,46, and 86 studies, respectively); (4) examining the title and abstracts of the selected literature to determine if the contents are in sharing and reuse contexts, such as information sharing, food sharing, car sharing, and accommodation sharing. After screening the relevant publications, the research targets became 168 publications (9,13,51,11,27,8,14,5, and 30 studies for each respective component); (5) analyzing the nine well-being components based on 168 target publications and organizing the critical links showing the antecedent or consequent relations of sharing and reuse behaviors; and finally (6) developing the motivational cycle and proposing the Hyper-Pyramid-Eco-System Model (HPES Model) based on the findings.
It is important to note that this study does not discuss the literature on the common sharing of language, culture, or memory, or on sharing behaviors among intimate people (such as family and friends). Moreover, well-being components are perceived before, during, and after sharing behaviors, but individuals cannot share well-being "themselves".  [24]. Figure 1. The research methodology of this study [24].
Next, we conducted a systematic literature review on the nine well-being components. The steps were as follows: (1) searching keywords by setting two terms at the same time; that is, combining a well-being component and sharing, such as "pleasure" and "sharing", through the title, abstract, and indexing search in Web of science and keyword in Google Scholar; (2) collecting the most relevant publications (4900 studies in total) and deleting the duplications of two datasets, leading to around 300 to 600 publications for each component; (3) eliminating the book, book chapter, non-English text, and unavailable full texts, leading to a decrease in the total number of publications to 617 (for each of the components there are 46,64,107,62,104,45,57,46, and 86 studies, respectively); (4) examining the title and abstracts of the selected literature to determine if the contents are in sharing and reuse contexts, such as information sharing, food sharing, car sharing, and accommodation sharing. After screening the relevant publications, the research targets became 168 publications (9,13,51,11,27,8,14,5, and 30 studies for each respective component); (5) analyzing the nine well-being components based on 168 target publications and organizing the critical links showing the antecedent or consequent relations of sharing and reuse behaviors; and finally (6) developing the motivational cycle and proposing the Hyper-Pyramid-Eco-System Model (HPES Model) based on the findings.
It is important to note that this study does not discuss the literature on the common sharing of language, culture, or memory, or on sharing behaviors among intimate people (such as family and friends). Moreover, well-being components are perceived before, during, and after sharing behaviors, but individuals cannot share well-being "themselves".

Exploring Well-Being in a Sustainable Product-Service System
In the past few decades, a growing number of studies regarding sustainability and well-being have been published, and the design of the product-service system (PSS) has also attracted much attention [16,25,26]. Due to the advancement of information and communication technologies, the possibilities of sharing and reuse have expanded from offline to online and from acquaintances to strangers worldwide [12]. During the 1990s, sharing online, consisting primarily of digital items, allowed people to share information and collaborate in digital spaces, such as Craigslist and Wikipedia. In recent decades, many successful PSS platforms that utilize online communities to connect off-line resources have emerged, including Couchsurfing, Airbnb, Uber, and Freecycle. In 2010, the book What's Mine is Yours: The Rise of Collaborative Consumption shed light on this novel socioeconomic model which provides individual satisfaction, social benefits, and environmental advantages compared to traditional industries. Moreover, a sustainable PSS enables the broad use of company-owned or privately shared products and facilitates a new collaborative lifestyle [12].
However, alongside the increasing interest in the well-being perspectives of the circular economy, there are also criticisms and debates associated with it. The exact social and ecological impacts of a sustainable PSS are complicated and difficult to determine [27]. Several studies indicate that users participate in a sustainable PSS platform more for their own benefit (e.g., cost and reward) than for social and environmental benefits [28]. The issues related to well-being in a sustainable PSS are still challenging; therefore, more research on sustainability and well-being is required for future development.
This section starts by explaining two foundations of this research: the P2P sharing and reuse platform, and well-being components. Whereas the former forms the context that users and participants interact with and constrains the research scope of this study, the latter is the emotions or internal states that direct the flow of the users' behaviors; that is, sharing and reuse, which are the research targets of this study.

The Peer-to-Peer Sharing and Reuse Platform
The peer-to-peer (P2P) sharing and reuse platforms, a type of two-sided platform that enables direct interactions between two different groups of participants (providers and consumers), can provide opportunities for social interaction [29]. In this study, we refer to consumers as receivers, who can receive goods or services from providers with or without money exchange. P2P sharing and reuse platforms can be characterized as follows: (1) exchanges occur between two sides of users through online platform mediation, (2) the two sides of users act as peers without hierarchy, (3) access on platforms is based on an equal exchange or through market mechanisms, and (4) the exchanged assets can be tangible or intangible and can be underutilized, such as idle space or skills (more details in [30][31][32]).
In a P2P sharing and reuse platform, providers and receivers are the most important actors, who exchange goods and co-create value. The platforms serve as the "matchmakers", who intermediate the matching of users, facilitate the exchange of goods or services and social relationships, and establish common norms within the network [33,34]. Three major interactions take place in a P2P sharing and reuse platform ( Figure 2): information exchange, objects (or services) exchange, and currency exchange [33]. Accordingly, we propose that information exchange can be further divided into three different features: user profile, object description, and communication, which may influence trust, pricing, perception of reciprocity, and sharing intentions [35][36][37][38]. In general, providers build their user profiles and list their shared or reusable objects (services), while receivers search that information and interact with providers to gain objects or services on the online platform. Following the completion of the deal and payment through the platform, they share and access the assets offline. However, the exact interaction steps are determined by the platform design and the service they provide.

How the Concept of Well-Being Works in Sharing and Reuse Contexts
The definition of well-being is still being explored, and no unified perspective has been achieved from different disciplines. According to the mainstream research on wellbeing, it can be mainly divided into hedonic well-being and eudemonic well-being, which are rooted in different aspects of human nature. Hedonic well-being is concerned with increasing positive emotions and decreasing negative emotions, while eudemonic wellbeing is concerned with fulfilling one's human potential and achievements [39]. Some researchers structure well-being according to its dimensions or elements. Ryff [40] summarizes well-being into six dimensions of life: self-acceptance, positive social relationships, autonomy, individual growth, environmental mastery, and purpose in life. Moreover, Seligman [41] proposes that well-being is measured in terms of flourishing, specifically a set of elements for a flourishing life: positive emotion, engagement, relationships, meaning, and accomplishment (PERMA). In contrast, some studies propose the multi-level nature of well-being. According to Nelson and Prilleltensky [42], well-being consists of the personal (e.g., self-esteem, independence), inter-personal (e.g., supportive relationships and engagement in society), and collective levels of well-being (e.g., ability to acquire community resources). They emphasize that well-being involves not only an individual's own well-being but also how that individual interacts with others and lives in a particular environment. In our view, well-being is correlated with human needs and motivations. Maslow [43] states that people fulfill various needs according to a hierarchical structure, which includes physiological needs, safety, love and belonging, esteem, cognitive needs, aesthetic needs, self-actualization, and transcendence. Additionally, Maslow's hierarchy of needs illustrates the hedonic and eudemonic perspectives on human needs.
In this study, we intend to integrate and simplify the various perspectives and explore three aspects of well-being, namely, intra-personal, inter-personal, and extra-personal aspects [24], to integrate well-being components into a sustainable PSS. Based on the perspectives of Nelson and Prilleltensky [42], and Calvo and Peters [24], we exemplify the intra-personal, inter-personal, and extra-personal aspects of well-being in a sustainable PSS and connect them with Maslow's hierarchy of needs [43]; see Figure 3.
• Intra-personal: The well-being components are experienced within the self or with an inanimate object. The affective experience is independent of the presence of others, such as pleasure and attachment toward an object, which can be a product or service, tangible or intangible.

How the Concept of Well-Being Works in Sharing and Reuse Contexts
The definition of well-being is still being explored, and no unified perspective has been achieved from different disciplines. According to the mainstream research on well-being, it can be mainly divided into hedonic well-being and eudemonic well-being, which are rooted in different aspects of human nature. Hedonic well-being is concerned with increasing positive emotions and decreasing negative emotions, while eudemonic well-being is concerned with fulfilling one's human potential and achievements [39]. Some researchers structure well-being according to its dimensions or elements. Ryff [40] summarizes well-being into six dimensions of life: self-acceptance, positive social relationships, autonomy, individual growth, environmental mastery, and purpose in life. Moreover, Seligman [41] proposes that well-being is measured in terms of flourishing, specifically a set of elements for a flourishing life: positive emotion, engagement, relationships, meaning, and accomplishment (PERMA). In contrast, some studies propose the multi-level nature of well-being. According to Nelson and Prilleltensky [42], well-being consists of the personal (e.g., self-esteem, independence), inter-personal (e.g., supportive relationships and engagement in society), and collective levels of well-being (e.g., ability to acquire community resources). They emphasize that well-being involves not only an individual's own well-being but also how that individual interacts with others and lives in a particular environment. In our view, well-being is correlated with human needs and motivations. Maslow [43] states that people fulfill various needs according to a hierarchical structure, which includes physiological needs, safety, love and belonging, esteem, cognitive needs, aesthetic needs, self-actualization, and transcendence. Additionally, Maslow's hierarchy of needs illustrates the hedonic and eudemonic perspectives on human needs.
In this study, we intend to integrate and simplify the various perspectives and explore three aspects of well-being, namely, intra-personal, inter-personal, and extra-personal aspects [24], to integrate well-being components into a sustainable PSS. Based on the perspectives of Nelson and Prilleltensky [42], and Calvo and Peters [24], we exemplify the intra-personal, inter-personal, and extra-personal aspects of well-being in a sustainable PSS and connect them with Maslow's hierarchy of needs [43]; see Figure 3.

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Inter-personal: The well-being components depend on the interaction between the self and others. Through a P2P platform, users exchange and communicate with each other and experience positive affects (e.g., trust, empathy, gratitude). • Extra-personal: The well-being components are transcendent concerns or actions for goods, beings, and cosmos beyond the self. In such an experience, one feels the unity of all things and aims to fulfill one's full potential (e.g., engagement, compassion, and altruism). To examine the relationship between the providers, receivers, and shared objects, we reviewed and integrated related literature concerning psychological, social, and environmental motivations or needs in various sharing and reuse contexts. The following is the list of nine essential well-being components in the sharing and reuse contexts (also see Table 1), for which we adapt the well-being factors for positive computing from Calvo and Peters [24] to fit the contexts of a sustainable PSS. This list is not exhaustive, but we detail the research evidence for and applications of each component below: • Pleasure: This is a positive influence that is fundamental and essential to the perception of well-being [44]. The need for pleasure ensures that animals are attracted to food, sex, or social interactions, leading to survival and reproduction [45]. Since owning and sharing possessions induces pleasure, scholars emphasize sharing and reusing rather than owning in the new era [46]. In addition, sharing tangible and intangible things generates pleasure. For example, sharing food online and offline facilitates social connections, and increases pleasure [47,48] and the appeal of food [48]. Furthermore, sharing home-grown food fosters social connections and motivates residents to share more [40]. By sharing intangible things (such as information, images, and ideas), people also feel the altruistic pleasure of helping others [47,[49][50][51], etc. • Attachment: This is the close bond developed between a baby and a mother (or a caregiver) through which the baby feels connected and secure [52]. In the sharing and reuse context, attachment can be extended toward inanimate things, such as an object or an environment. A strong attachment to an object motivates people to take good care of it and increases well-being [53]. Sellers who have a higher attachment to used products are more likely to offer discounts to buyers who will be able to use them appropriately [54]. For example, the presence of personal objects that evoke perceptions of the host's presence can improve guests' attachment to their hosts [55]. Attachment toward an accommodation can increase the intention to use recommendation sharing [56], etc.

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Trust: This can be defined as an attitude in which a person relies on and believes another to behave as expected in an uncertain and vulnerable situation [57]. Trust allows people to perceive security, support, and comfort, and facilitates pro-social behavior [58]. It plays a crucial role in P2P platforms [59,60], where users share • Intra-personal: The well-being components are experienced within the self or with an inanimate object. The affective experience is independent of the presence of others, such as pleasure and attachment toward an object, which can be a product or service, tangible or intangible.

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Inter-personal: The well-being components depend on the interaction between the self and others. Through a P2P platform, users exchange and communicate with each other and experience positive affects (e.g., trust, empathy, gratitude). • Extra-personal: The well-being components are transcendent concerns or actions for goods, beings, and cosmos beyond the self. In such an experience, one feels the unity of all things and aims to fulfill one's full potential (e.g., engagement, compassion, and altruism).
To examine the relationship between the providers, receivers, and shared objects, we reviewed and integrated related literature concerning psychological, social, and environmental motivations or needs in various sharing and reuse contexts. The following is the list of nine essential well-being components in the sharing and reuse contexts (also see Table 1), for which we adapt the well-being factors for positive computing from Calvo and Peters [24] to fit the contexts of a sustainable PSS. This list is not exhaustive, but we detail the research evidence for and applications of each component below:

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Pleasure: This is a positive influence that is fundamental and essential to the perception of well-being [44]. The need for pleasure ensures that animals are attracted to food, sex, or social interactions, leading to survival and reproduction [45]. Since owning and sharing possessions induces pleasure, scholars emphasize sharing and reusing rather than owning in the new era [46]. In addition, sharing tangible and intangible things generates pleasure. For example, sharing food online and offline facilitates social connections, and increases pleasure [47,48] and the appeal of food [48]. Furthermore, sharing home-grown food fosters social connections and motivates residents to share more [40]. By sharing intangible things (such as information, images, and ideas), people also feel the altruistic pleasure of helping others [47,[49][50][51], etc. • Attachment: This is the close bond developed between a baby and a mother (or a caregiver) through which the baby feels connected and secure [52]. In the sharing and reuse context, attachment can be extended toward inanimate things, such as an object or an environment. A strong attachment to an object motivates people to take good care of it and increases well-being [53]. Sellers who have a higher attachment to used products are more likely to offer discounts to buyers who will be able to use them appropriately [54]. For example, the presence of personal objects that evoke perceptions of the host's presence can improve guests' attachment to their hosts [55]. Attachment toward an accommodation can increase the intention to use recommendation sharing [56], etc.
• Trust: This can be defined as an attitude in which a person relies on and believes another to behave as expected in an uncertain and vulnerable situation [57]. Trust allows people to perceive security, support, and comfort, and facilitates pro-social behavior [58]. It plays a crucial role in P2P platforms [59,60], where users share belongings with strangers, especially while sleeping at others' homes [61][62][63][64][65]. Möhlmann and Geissinger [66] identify six design features that establish trust in the sharing economy: peer reputation, digitalized social capital, information provision, escrow services, insurance cover, and certification/external validation. Additionally, one study indicates that the quantity of information and communication between a provider and a receiver [65], the duration of self-description and diversity of topics of hosts in self-disclosure [36], and the humanization of profile pictures [38] are important factors to build trust. Moreover, the trustworthiness of the host's personal photo increases the listing price and the probability of its being selected [35].

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Empathy: This is regarded as the mental process of eliciting emotions in response to others' traits and conditions, as well as understanding the reasons behind these emotions [67]. Empathy is an emotional response based on the perception of others' well-being [68]. In the sharing and reuse context, the empathy of receivers toward providers increases their willingness to make a purchase [69]. In addition, business and personal information disclosures between a seller and a buyer have a positive impact on empathy and business performance [70]. There is evidence that empathy prevents customers from leaving negative reviews [71,72]. • Contribution: The concept of contribution refers to a person's positive impact on others and their fulfillment of the basic psychological needs of autonomy, relatedness, and competence [73]. It can strongly predict the eudemonic well-being of oneself [74].
Concerning the sense of contribution in the sharing and reuse context, self-worth serves as an important intrinsic motivation to promote sharing of mobile coupons in social media [75]. Another study has shown that an organizational sense of contribution positively correlates with the intention of information system personnel to share knowledge [76].

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Gratitude: This is a feeling of appreciation when one receives favors, kindness, help, and support from others [77]. One can feel gratitude for not only inter-personal relationships but also for an object or an experience, such as artwork or a trip [78].
Research shows that practicing gratitude improves well-being (e.g., [79][80][81]). Gratitude appeal encourages word-of-mouth for sustainable luxury brands [82]. Furthermore, posting grateful reviews of firms will encourage other consumers to reward firms [83]. The gratitude between a salesperson and customer fosters the prosocial behaviors (e.g., information sharing) of a salesman, thus developing long-term buyer-seller relationships [84]. • Engagement: This refers to the state of being immersed in an activity or experience. It is also regarded as an optimal experience, "flow" [85,86]; moreover, it is defined as an exceptional and enjoyable experience that leads to the attainment of well-being [87]. Scholars indicate that a sense of ownership is the antecedent to engagement, including loyalty to a brand (or platform), contributions to its reputation, service functionality, and community-oriented sharing [88]. Additionally, inter-personal contamination (e.g., bad hygiene, intrusion of privacy) has negative effects on engagement in accommodation sharing, but the authenticity (e.g., providing more information about hosts, sharing their living space, and building a closer relationship between the host and the guest) can alleviate these negative effects, improving the engagement in sharing experiences [89,90].

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Compassion: This is an attitude of caring for others and a willingness to assist them in their suffering [91,92]. Additionally, treating oneself, others, and the environment with compassion improves individuals' well-being and mental health [92][93][94]. Empathy and compassion are fundamental for the prosperity of social relationships. Furthermore, compassion enables people not only to share others' emotions but also to help oth- ers [95]. According to a study, people who have high levels of trust and compassion for others are significantly more willing to share shelters and vehicles following disasters. In addition, the role of people (volunteers in past disasters and members of community organizations) rather than idle resources influences willingness to share [96].

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Altruism: This is regarded as a behavior rather than an emotion that gives benefits to others at the expense of oneself [97]. Altruism is based on empathy and compassion [68,98], which encompasses both inter-personal and extra-personal actions. In the sharing context, altruism and trust attract considerable attention. There is evidence that trust improves knowledge-sharing intentions, and altruism has a positive impact on the relationship between trust and knowledge-sharing intentions in teacher communities [99]. In particular, the trait of altruism impacts sharing intentions and lowers the need for trust [100]. Volunteers for the Wikipedia Foundation found that altruism motivates them to contribute to society continuously [101,102].

Intrapersonal Pleasure
A positive effect that is fundamental to the perception of well-being [44].

Attachment
A close bond between a baby and a caregiver to feel connected and secure [52].
Interpersonal Trust An attitude in which a person believes and relies on one another to behave as expected in an uncertain and vulnerable situation [57].
Empathy A mental process in which emotions are elicited by others' traits and conditions, and the reasons behind these emotions [67].

Contribution
A positive impact on others that fulfills one's human needs of autonomy, relatedness, and competence [73].

Gratitude
A feeling of thankfulness when one receives favors, kindness, help, and support from others [77].

Extrapersonal Engagement
A state of being immersed in an activity or experience, and the optimal condition can be called a "flow" [85,86].

Compassion
A caring attitude and willingness to help others who are suffering [91,92]. Sharing shelter, relief supplies [96], etc.
Altruism A behavior rather than an emotion, which benefits others at the expense of oneself [97].

The Motivational Cycle of Well-Being in a Sustainable PSS
As we have discussed previously, the results from several related studies demonstrate that each well-being component may be antecedent or consequent of sharing behavior. As shown in Figure 4, the perception of gratitude and contribution have a positive impact on the motivation to share information. After information sharing, users perceive a sense of trust and empathy toward others as well as attachment toward the shared objects. The feelings of trust and empathy facilitate the feeling of compassion, while attachment influences the sense of ownership, which in turn evokes the feeling of engagement in sharing objects. Ultimately, the sharing of objects arouses a feeling of pleasure and a sense of contribution. The findings of the relationships of well-being components in the sharing contexts mainly are two: (1) the antecedents of sharing behaviors are inclined to the allocentric well-being components (gratitude, contribution, compassion, altruism, and engagement) and the consequents are rather egocentric, which are trust, empathy, attachment, pleasure; (2) contribution occurs at two times in the whole process, at the beginning and at the end. As a result, the sharing process is formed into a cycle, and the potential to develop sustainable sharing is demonstrated.
jects. The feelings of trust and empathy facilitate the feeling of compassion, while attachment influences the sense of ownership, which in turn evokes the feeling of engagement in sharing objects. Ultimately, the sharing of objects arouses a feeling of pleasure and a sense of contribution. The findings of the relationships of well-being components in the sharing contexts mainly are two: (1) the antecedents of sharing behaviors are inclined to the allocentric well-being components (gratitude, contribution, compassion, altruism, and engagement) and the consequents are rather egocentric, which are trust, empathy, attachment, pleasure; (2) contribution occurs at two times in the whole process, at the beginning and at the end. As a result, the sharing process is formed into a cycle, and the potential to develop sustainable sharing is demonstrated. In addition, to facilitate users' sustainable behaviors, we develop the motivational cycle based on the habit loop (cue-routine-reward loop) [106] and our findings ( Figure 5). In the beginning, the users focus more on their egocentric benefits, so they are motivated to achieve their expected utility. At the same time, this can be designed as a cue to initiate the process of matching their expected utility by sharing information about their needs. For example, when students want to buy a cheap textbook, an online second-hand store is akin to a cue popping into their heads. In the following, the well-being components and the object-sharing behaviors are aroused as well. The cycle inside is a well-being cycle through which people can perceive positive emotions and develop the routine. The platform can facilitate the perception of trust and empathy during information sharing. For example, the ride-sharing service, blablacar, shows the drivers' pet preferences and music habits to facilitate a closer relationship. After having the sharing behaviors, which provide people the feeling of contribution, the cycle continues to circulate when people experience intrinsic and extrinsic motivation; that is, the actual utility. Here, it is worth noting that a platform can be designed to facilitate the tangible or intangible rewards. Since people expect to gain achievements, platforms can provide some gamification systems, such as badges, points, or leader boards, to visualize the contribution as a reward. This motivation Figure 4. The relationships among well-being components in sharing and reuse contexts [35,47,48,55,65,70,75,76,82,84,88,90,96,99].
In addition, to facilitate users' sustainable behaviors, we develop the motivational cycle based on the habit loop (cue-routine-reward loop) [106] and our findings ( Figure 5). In the beginning, the users focus more on their egocentric benefits, so they are motivated to achieve their expected utility. At the same time, this can be designed as a cue to initiate the process of matching their expected utility by sharing information about their needs. For example, when students want to buy a cheap textbook, an online second-hand store is akin to a cue popping into their heads. In the following, the well-being components and the object-sharing behaviors are aroused as well. The cycle inside is a well-being cycle through which people can perceive positive emotions and develop the routine. The platform can facilitate the perception of trust and empathy during information sharing. For example, the ride-sharing service, blablacar, shows the drivers' pet preferences and music habits to facilitate a closer relationship. After having the sharing behaviors, which provide people the feeling of contribution, the cycle continues to circulate when people experience intrinsic and extrinsic motivation; that is, the actual utility. Here, it is worth noting that a platform can be designed to facilitate the tangible or intangible rewards. Since people expect to gain achievements, platforms can provide some gamification systems, such as badges, points, or leader boards, to visualize the contribution as a reward. This motivation cycle structures the behavioral mechanism of users and demonstrates how to share and reuse objects prosperously and sustainably.

The Conceptual Framework of Well-Being in a Sustainable PSS
After reviewing the related studies, we explore these components based on human needs to propose a preliminary framework of a sharing ecosystem with well-being and

The Conceptual Framework of Well-Being in a Sustainable PSS
After reviewing the related studies, we explore these components based on human needs to propose a preliminary framework of a sharing ecosystem with well-being and organize the motivations of sharing and reuse. Specifically, we investigate the relations between the egocentric and allocentric perspectives of well-being.

The Hyper-Pyramid-Eco-System Model (HPES Model)
Referring to Figure 3, the five upper components of allocentric well-being, namely, contribution, gratitude, engagement, compassion, and altruism, are found to be the antecedents for increasing the willingness to share and reuse (Figures 4 and 5). Moreover, contribution and gratitude motivate information-sharing behavior, while engagement, compassion, and altruism facilitate object sharing. Inter-personal components (trust, empathy, and contribution) serve as the pivots which are the consequents of information sharing and the antecedents of object sharing. In contrast, the two lower components of intra-personal well-being, pleasure, and attachment are consequences of sharing. This finding suggests that how we foster sharing and reuse should be geared more toward inter-personal and extra-personal well-being than intra-personal well-being.
Thus, we propose the conceptual model to shed light on how to facilitate users' transition from intra-personal to inter-personal and extra-personal motivation in a comprehensive vision. We develop the Hyper-Pyramid-Eco-System model of the P2P sharing platform (HPES model), which illustrates the whole view of well-being equipped in the circular economy ( Figure 6). A thorough understanding of the HPES model can be gained by looking at it from the inside to the outside. The inside of the pyramid displays the fundamental relationship among the four main actors (self, other, object, and platform). The links between actors illustrate the aspects of relationships (i.e., intra-personal, inter-personal, and extra-personal aspects). The self-object link is an intra-personal relationship, the self-other is an inter-personal relationship, and the other-object is an extra-personal relationship. Moreover, they correspond to the well-being components, namely, the self-object link to pleasure and attachment, the self-other to trust, empathy, contribution, and gratitude, and the other-object to engagement, compassion, and altruism. The two circular arrows (blue and orange arrows) around the four actors illustrate egocentric and allocentric motives that demonstrate the process of moving from owning an object (the representation of ), sharing it with others to obtain social interaction (the representation with), and helping others in pursuit of higher goals, such as self-actualization (the representation for). Three elements on the outside of the pyramid (well-being, society, and the environment) portray what people are surrounded by and how we can interact with them. Accordingly, well-being is connected to the self, society is the other, and the environment is the object. In addition, these three elements serve as life goals that can be pursued to attain sustainable development. Using this model, we can construct a global and local view of how the sharing economy can be used to interact with individuals, society, and the environment. These findings of well-being components in the P2P platform are expected to not only motivate the actors (providers, receivers, and platforms) to consider well-being but also to encourage them to share and reuse objects prosperously and sustainably.

Well-Being-Based Design Guidelines for P2P Sharing and Reuse Platform
Based on the core functions (pulling, facilitating, and matching) of platform design [33], we propose design guidelines to foster sharing and reuse sustainably. In the P2P sharing and reuse platforms, where users have the potential to develop social relationships and pursue self-actualization, we anticipate proposing additional values of well-being to elevate the P2P sharing and reuse ecosystem. the object. In addition, these three elements serve as life goals that can be pursued to attain sustainable development. Using this model, we can construct a global and local view of how the sharing economy can be used to interact with individuals, society, and the environment. These findings of well-being components in the P2P platform are expected to not only motivate the actors (providers, receivers, and platforms) to consider well-being but also to encourage them to share and reuse objects prosperously and sustainably. Figure 6. The Hyper-Pyramid-Eco-System model of the sustainable product-service system.

Well-Being-Based Design Guidelines for P2P Sharing and Reuse Platform
Based on the core functions (pulling, facilitating, and matching) of platform design [33], we propose design guidelines to foster sharing and reuse sustainably. In the P2P sharing and reuse platforms, where users have the potential to develop social relationships and pursue self-actualization, we anticipate proposing additional values of wellbeing to elevate the P2P sharing and reuse ecosystem.

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Pulling: This attracts providers and receivers to join in the sharing and reuse platforms, and regularly revisit them. In the beginning, it is challenging for a platform to attract users because of the "chicken-or-egg" problem, where users will not come to a platform if they feel there is no value, and a platform cannot create value without users [33]. Therefore, the platform design must address how to overcome this problem first and increase the number of users to initiate the network effect. The perception of contribution and gratitude are found to play significant roles in initiating users to share information when combined with the findings of the well-being components and the sharing behaviors. After sharing and reusing, people can perceive achievement and contribution naturally. Thus, platforms can encourage new providers to join the platform, with emphasis on contribution as well to facilitate circulation. For example, the commercials may focus on "contributing to society" instead of "saving cost", and nudge users with messages, such as "Share knowledge with your colleagues, contribute to the whole campus".

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Facilitating: This removes barriers and encourages value-creating interactions, such as sharing and collaboration. The mission is to ensure that the providers and receivers interact and exchange values properly. The well-designed platform adheres to the principles of transparency and insurance to ensure the safety of its users. Since platforms attract a wide range of users, they require governance and management to establish trust, equity, and security [33]. In the previous section, we found that information sharing is the key interaction between the two sides of users, serving as a Figure 6. The Hyper-Pyramid-Eco-System model of the sustainable product-service system.

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Pulling: This attracts providers and receivers to join in the sharing and reuse platforms, and regularly revisit them. In the beginning, it is challenging for a platform to attract users because of the "chicken-or-egg" problem, where users will not come to a platform if they feel there is no value, and a platform cannot create value without users [33]. Therefore, the platform design must address how to overcome this problem first and increase the number of users to initiate the network effect. The perception of contribution and gratitude are found to play significant roles in initiating users to share information when combined with the findings of the well-being components and the sharing behaviors. After sharing and reusing, people can perceive achievement and contribution naturally. Thus, platforms can encourage new providers to join the platform, with emphasis on contribution as well to facilitate circulation. For example, the commercials may focus on "contributing to society" instead of "saving cost", and nudge users with messages, such as "Share knowledge with your colleagues, contribute to the whole campus". • Facilitating: This removes barriers and encourages value-creating interactions, such as sharing and collaboration. The mission is to ensure that the providers and receivers interact and exchange values properly. The well-designed platform adheres to the principles of transparency and insurance to ensure the safety of its users. Since platforms attract a wide range of users, they require governance and management to establish trust, equity, and security [33]. In the previous section, we found that information sharing is the key interaction between the two sides of users, serving as a pivot for allowing the users to get to know each other, engaging in social interaction, and developing a sense of well-being in the sharing platforms. Additionally, we conclude that information disclosure promotes trust and empathy. It is interesting to note that providers with a higher attachment toward objects intend to provide more benefits to receivers if they know that the receivers will treat their objects with care [54].
Since the receiver uses the shared objects appropriately, it reflects the sympathy and understanding between providers and receivers. Empathy serves as the key element to link the provider's and the receiver's mind. Therefore, we assume that empathy from receivers can arouse providers' positive intentions and encourage them to disclose more information. In addition, trust and gratitude are found to positively impact users' intentions to be "prosumers" on the sharing platforms [107]. It means that one-side users are more motivated to join the other side, i.e., a provider becomes a receiver and vice versa. Trust should be fostered to increase engagement among two sides of users in the sharing contexts. We believe it is not just the reputation score, but also the profile texts, personal photos, and communication, which create attached, reliable, and familiar experiences that can influence how others trust and develop empathy. Moreover, communication between a provider and a receiver is crucial to increase empathy and altruism, especially when a receiver asks questions instead of receiving one-way communication from a provider [108]. Therefore, we suggest that the design of the user profile, object description, and communication should nudge users to have more well-being-based information sharing to arouse positive perceptions. • Matching: It builds an efficient mechanism to match the relevant providers to receivers. The platforms accurately match the needs of users with objects or services based on the information provided by them. The information can be statistical (such as gender, nationality) or dynamic (such as date, location). Additionally, platforms utilize a large amount of data to refine matching algorithms and filter the information exchange between providers and receivers [33]. We suggest the platform design should be devoted to matching users who experience more empathy and trust. For example, similar background users can arouse more empathy, and people who have more authentic self-disclosure can increase trust. After a provider and a receiver share information, as well as build trust and empathy toward each other, the perception of compassion and altruism can be aroused as follows. Users maximize the utility for not only their own benefits, but also the well-being of objects, society, and the environment. Thus, the platform should support users to increase positive interactions, and maximize utility through sharing and reusing objects. Finally, the well-beingbased guidelines can arouse behavior changes in users from exchanging information, reusing, and sharing an object, to engaging sustainably.

Prospective Approaches for Modeling Well-Being Components in a Sustainable PSS
To understand the overall users' thoughts and behaviors under the P2P sharing and reuse contexts, we suggest the following two approaches: data-driven and computational neuroscience. Both approaches can be tested and integrated into different methods to improve the design for the sustainable PSS [109,110]. The difference is that the datadriven approach is executed in the existing platform, while the computational neuroscience approach is suitable for testing in an experimental environment.

Data-Driven Approach
The data-driven approach can provide a direct way to analyze and compare the providers' and receivers' behaviors by using real-life datasets. As the previous section mentions, some research examined the trust based on providers' personal photos [35,38], the topics, and lengths of profiles [36], and thus determine price [37]. Similarly, other interpersonal components (such as attachment and empathy) can be examined in a data-driven approach. The providers showing attachment to their possessions and the receivers stating positive intentions can arouse empathy between them and increase the possibility of sharing the objects. Therefore, the parameters, such as sharing intentions, lengths, and details of object description, reviews, and prices, can be compared among similar exchange cases. It should be noted that the results may reveal unexpected information either in a good or a bad way under a data-driven environment. In this kind of method, the researchers can test hypotheses on real-world data extracted from extant platforms. For example, the well-being components can be tested based on the similarity of the providers' and receivers' characteristics, such as age, income, or income divisions [23], to understand the intensities of empathy.

Computational Neuroscience Approach
Compared to the data-driven approach that extracts external information based on human behaviors, the computational neuroscience approach provides a different perspective to research on human internal states. Active inference as a united approach to explaining the human brain and mind has gained growing popularity recently. It models the neurocognitive processes inside humans and the reactions between humans and the environment (i.e., perception and action) [111]. Active inference can show not only the human's internal states but also the contextual and social factors which affect human perception and action. In addition, based on the concepts that all the adaptions of organisms need to minimize free energy [112], it applies the free energy principles to explain how we predict, perceive, and react based on our generative models, beliefs of hidden states, and observation of the world. Active inference helps explain human emotions [20,21,113,114], communication [115], and subjective well-being [116]. Especially, in the past, well-being was mainly evaluated by selfreport, but the free energy principles and active inference provide computational ways of explaining the complex mental mechanisms and how people attain higher well-being [116]; these principles are rather new and have the potential to be developed. In the setting of active inference experiments, researchers can design the platform layouts and test the participants' behaviors and subjective assessments to examine the perception and inference of well-being components. Taking empathy as an example, participants receive virtual sharing information and may infer that an other-sided user who has a similar background is more empathetic and intentional to share with.

Conclusions
This study investigated how to infuse well-being components into the circular economy. Based on the literature review, we organized and analyzed the extant evidence of related well-being-based research to develop an ecosystem model of a sustainable PSS, especially a P2P sharing and reuse platform, and examined the potential relationships among all well-being components and sharing behaviors. We proposed that both egocentric growth and allocentric growth of well-being need to be considered in a sustainable PSS. We intended to encourage users who are motivated by egocentric benefits to adopt an allocentric perspective. Thus, we provided the HPES model and well-being-based design guidelines to draw people's attention to the inter-personal well-being (trust, empathy, and contribution) and extra-personal elements (compassion and altruism) present on P2P sharing platforms to circulate sharing and reuse behaviors. In addition to structuring the well-being components, we also found that information sharing was crucial for initiating a flow of perceptions of well-being and sharing behaviors. Information exchanged on platforms can be enhanced by improving user profiles, object descriptions, and communication. Finally, we discussed the data-driven and active inference approaches for further study.
This study has certain limitations that should be considered when interpreting the results. First, the relevant literature was screened by searching for established well-being keywords; however, there may be other relevant keywords that were not considered. Second, the books, book chapters, unavailable full-texts, and publications written in non-English were excluded from the literature review, but the omitted literature may have relevant information needed on this topic. Thirdly, the proposed frameworks in this research are based on the findings published by different studies. The motivational cycle and the HPES model are concepts and still need to be examined further in the identical sharing and reuse context. Despite these limitations, this study has provided insight that will guide practitioners and researchers to adopt a well-being perspective in P2P sustainable business models. The major contributions of this study are that the well-beingbased motivational cycle and the HPES model shed light on the novel perspective to focus on the flows and interactions among each role in the sustainable PSS; the study can provide directions for improvements to individual well-being and promote the sustainability of society and the environment. Funding: This research is part of the results of Value Exchange Engineering, a joint research project between R4D; Mercari, Inc. and RIISE.
Institutional Review Board Statement: Not applicable for this study since it does not involve humans or animals.
Informed Consent Statement: Not applicable for this study since it does not involve humans.

Data Availability Statement:
No new data were created or analyzed in this study. Data sharing is not applicable to this article.