Seven Cognitive Concepts for Successful Sustainable Design

Proceedings of the ASME 2012 International Design Engineering Technical Conferences & Computers and Information in Engineering Conference IDETC/CIE 2012 August 12-15, 2012, Chicago, IL, USA

DETC2012-70676 SEVEN COGNITIVE CONCEPTS FOR SUCCESSFUL SUSTAINABLE DESIGN Erin MacDonald Interdisciplinary Research In Sustainable Design Department of Mechanical Engineering Iowa State University Ames, Iowa, 50010 E-mail: [email protected] ABSTRACT For the past forty years, social science researchers have studied how to encourage pro-environmental behaviors such as the adoption of recycling programs, water conservation strategies, and purchase of sustainable products. This article presents a synthesis of these research findings as they relate to the design of sustainable products and technologies. Research from environmental psychology, consumer studies, economics, decision sciences, public policy, and behavioral psychology are organized into cognitive concepts that are crucial to the successful purchase and use of sustainable products. The cognitive concepts reviewed are: responsibility, complex decision-making skills, decision heuristics, the altruismsacrifice link, trust, cognitive dissonance/guilt, and motivation. Product examples are provided to highlight the role of these cognitive concepts in sustainable design. Design recommendations and relevant design methods are discussed. The recommendations require dynamic and on-going coordination between designers, manufacturers, marketers, and government policy-makers to achieve positive changes in individuals’ behaviors. The success of sustainable products depends on the success of this coordination. 1 INTRODUCTION For the past forty years, social science researchers have studied how to encourage the adoption of recycling programs, water conservation strategies, and other individual sustainability efforts. Below is a synthesis of some of these research findings as they relate to the design of sustainable products and technologies. This article first defines the boundaries of the surveyed literature. Then it gives an overview of relevant terms such as “attitude” and “pro-environmental behavior” (PEB). The rest of the article is devoted to exploring the seven cognitive concepts, interspersed with

Jinjuan She Interdisciplinary Research In Sustainable Design Department of Mechanical Engineering Iowa State University Ames, Iowa, 50010 E-mail: [email protected] recommendations for designers and relevant emerging design methods. Consider a continuum of sustainable product success, shown in Fig. 1, as defined by the customer: some individuals actively seek out sustainable products to buy and use (strong purchase criteria); some do not seek them out, but will use a product’s sustainable feature to form a preference for the product over an otherwise identical alternative (weak purchase criteria); some individuals are neutral to sustainable products (neutral); and, unfortunately, some individuals find sustainability to be a drawback (negative purchase criteria)— for reasons to be explored later. Metaphorically speaking, this article aims to create “positive movement” along this continuum by inspiring engineering designers to design sustainable products that encourage such movement. Moving customers along this continuum towards the active pursuit of sustainable products, as conveyed by the arrow in Fig. 1, is advantageous both to the environment and the company producing the product. It is advantageous to policy-makers, as it can reduce the expense of time and money required to institute a new product-related policy. Increased demand, reduced environmental impacts, and easier policy implementation will all spur development of sustainable products. 1.1 Scope of Discussion The discussion here is centered on the design of massmarket sustainable products. The working definition of sustainable product used throughout this article is: a product that is intentionally and methodically designed to decrease environmental impact versus the status quo, be that a competing product or an otherwise-defined baseline, using a scientifically-based environmental impact assessment tool of the designer's choosing. The focus on mass-market indicates (a) products that individual customers can purchase directly; or (b)

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products that individuals can choose to use or accept. The latter could be complex decision, like a farmer allowing a wind turbine to be installed on his or her land, or a seemingly simple decision like deciding to use the air-blow hand dryer instead of paper towels to dry one’s hands.

Negative  Opinion

Neutral

Weak  Purchase  Criteria

Strong  Purchase  Criteria

FIGURE 1. A continuum of customer preference for sustainable products.

This article represents a synthesis of findings from literature in the fields of environmental psychology, behavioral environmental psychology, consumerism, and environmental political science. The literature presented focuses on research conducted in the United States and Europe. Summary and review articles are referenced wherever possible to aid the reader in furthering their education. The references presented should not be taken as a complete list of publications in all relevant fields; but rather a synthesis of the most useful perspectives. For a review of environmental psychology as a discipline, see Ref. [1] and the corresponding special issue of the Journal of Social Science, and a special issue of American Psychologist (see Ref. [2, 3]); for a review of green marketing, see Ref. [4], and note the recent special issue on sustainability from The Journal of the Academy of Marketing Science [5]; for a review of the psychology of forming preferences see Ref. [6]. For a review of motivating behavioral change and environmental policy implications (focused on the United Kingdom) see Ref. [7]. For a review of sustainable design theory in mechanical design see Ref. [8]. To further narrow the discussion, this article assumes that individuals are concerned about the negative impact they have on the environment, instead of attempting to address the equally-important issues of public awareness and environmental education. Guber provides an excellent analysis of public opinion concerning the environment and documents that the level of public concern for the environment varies widely by date and by survey framing [9]. She finds that while the environment is a top concern of U.S. citizens, it is not the top concern when ranked in a list of concerns; and individuals feel ambivalent addressing environmental issues when they consider other values and concerns. This article also does not attempt to solve the problem of accessibility to sustainable products in rural areas and/or people who do not have internet purchasing capabilities. 1.2 Types of Pro-environmental Behavior (PEB)

People have a number of options for acting on their environmental concerns through participating in different types of pro-environmental behavior (PEB). For example, consider that the author is concerned about the negative environmental effects of her use of coal-powered energy: she can diminish her use of electricity by turning off lights when not in use, classified as a curtailing behavior; she can hope to change her electricity source by voting and protesting for clean energy, classified as a political behavior; or she can reduce the electricity needed to perform her usual behaviors; such as installing compact fluorescent light bulbs (CFLs), classified as an efficiency behavior. Curtailing, political, and efficiency behaviors, visualized as influencing and overlapping with each other in Fig. 2, are a commonly used set of classifications for pro-environmental behaviors. The different types of behavior overlap and can be used to reinforce each other, as will be discussed. For a discussion of other classifications, see Ref. [10]. A mix of behaviors is often observed for people engaged actively in sustainability; some people prefer performing curtailing behaviors over efficiency behaviors and vice versa; these preferences correlate with demographic information as explained in [11]. The discussion below is tailored to encourage efficiency behaviors through the design of sustainable products. However, some of the concepts are applicable to all three categories of PEB.

FIGURE 2. Types of pro-environmental behaviors (PEB). Behavioral psychologists offer insights into the psychological precursors to performing a PEB. For a review of studies, see Ref. [10] whose Value-Belief-Norm theory provides a sympathetic conclusion to the discussion below: the causes for PEB are not always clear and a combination of corrective approaches works best when attempting to change behavior. One may think that positive feelings for the environment would be an indicator of likelihood to perform PEB; however, environmental attitude alone is not a good predictor of PEB [3, 12]. Vining et al. [13] review a number of studies to conclude that “measures of environmental concern are only weakly related to PEB." Intentions formed directly before performing a PEB have been found to be an indicator of PEB, but the strength of the link varies from study to study (Koehn 2006) [14]. Good intentions may not be acted upon because of a lack of knowledge required to address the complexities of PEB [10]. The majority of the population finds

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the required knowledge-gathering challenging, as will be discussed further. There is some evidence of “spillover” between curtailing behaviors. A study by Hutton [15] that found that distributing water-flow restrictors with energy-saving pamphlets to households led to a decrease not only in water usage, but also in energy and heat usage. However, a study of Danish consumers found that there is variable spillover of PEBs, and that the behaviors within different categorizations (such as recycling vs. buying organic food) are not closely related in peoples’ minds [16]. 2 THE SEVEN COGNITIVE CONCEPTS The cognitive path between attitudes and behaviors is indirect, and includes “functions” that influence the performance of PEB. Seven cognitive themes or concepts that influence PEB are particularly relevant to improving the design of sustainable products. These concepts are: responsibility, complex decision-making skills, decision heuristics, the altruism-sacrifice link, trust, cognitive dissonance/guilt, and motivation. This section provides explanations and examples of these cognitive concepts, with recommendations for designers. The examples are used to demonstrate how the recommendations may be applied. Due to the significant influence of public policy on engineering design decisions [17], some recommendations also involve coordination with policy makers. The concepts are presented in an order that allows the logical flow of conclusions and recommendations in the discussion; this order is not meant to suggest a temporal or hierarchical relationship between the concepts. An overview of the concepts, recommendations and corresponding evidence is presented in Table 1. The evidence is classified by its field of research: Design Research (DR), Technology Research (TR), Business Research (BR), Social Science Research (SR), and Research from Other Fields (OR). 2.1 Responsibility An individual sense of responsibility for current environmental problems can be separated into two parts: a sense of responsibility for causing the problems, and a sense of responsibility for solving the problems. The former, when felt as blame and/or guilt, can potentially decrease PEB, as will be discussed in Section 2.6. The latter, when properly guided, increases PEB. The environmental crisis is a duality between common tragedy and individual cause as exhibited in the awarding of the 2007 Nobel Peace Prize, split between the UN’s Intergovernmental Panel on Climate Change, a worldwide organization, and Al Gore, a single individual. The environmental "tragedy of the commons" is famously addressed in a parable by Hardin in Science [18]. There is a common pasture that will deteriorate to uselessness if sheep herders only act in their own short-term best interest. Both in this parable and in the real world of communal resource sharing, it is typically a community action that maintains communal resources, rather than individual ones [19]. The environmental

tragedy of the commons has been remarkably individualized. The individualization began in the 1960s, when naturalists popularized the environmental movement in books such as Silent Spring [20]. These books used generalizations and shock value, a “shame and blame” strategy, to make readers feel an individual sense of responsibility for environmental problems. The environmental movement was later commoditized (i.e. buy a “save the planet” T-shirt) during the individualistic 1980s [21]. The 1990s brought the publishing of best-selling books such as Green Consumer Guide [22, 23]. In Al Gore’s An Inconvenient Truth book [24], out of thirty-four recommendations for “what you personally can do to solve the climate crisis,” only four were community or politicallyfocused, and they were listed last. This duality allows individuals to push the responsibility to the “commons” and avoid difficult personal sustainability decisions and behaviors. The intersection of public policy and personal responsibility causes confusion in resolve: people are concerned enough about the environment to desire government to do something about it, but they themselves would prefer to make only voluntary changes as a result of this public policy [9]. Individuals can conveniently listen to the messages of hardcore environmentalists who undermine a sense of individual responsibility for the problem, viewing individual PEB as ineffective [21]. The majority of U.S. citizens assume that industry and government are already taking responsibility for environmental problems [9]. This avoidance is unfortunate, firstly because individual responsibility and PEB is necessary to initiate wide-scale policy changes efficiently and effectively. It is also unfortunate because an individual’s judgment of the extent to which they can personally prevent environmental destruction gives significant indication of their likelihood to purchase sustainable goods [25]. People feel like they do not have individual control over solving environmental problems— people do not think that their individual efforts will make a difference [26, 27]. Recommendation 1: Instill a sense of personal control of the solution, not responsibility for causing the problem, by designing products with interactive curtailing features. Build features into sustainable products that not only offer efficiency behaviors, but also opportunities to perform curtailing behavior on an elective and repetitive basis. Customers will thereby have multiple approaches to expressing individual PEBs through products. Allowing opportunities to increase the curtailing behaviors of product uses are included in current Design for Environment methods, summarized by Telenko et al. as a single principle: “Incorporate features that prevent waste of materials by the user” [28]. To reinforce a sense of responsibility in the user, the findings from social sciences suggest that an emphasis on features that are active and require participation in waste reduction rather than passive waste prevention will go further to promote PEB. The ideal design would include waste-reduction features that the user interacts with on a regular basis and feels a small reward for

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Toyota Prius panel encourages drivers to achieve higher MPGs Real-time feedback on home electronics increases energy savings

3. Encourage tackling of complex decisions through interaction incentives and designing-in educational feedback

“Clean Air Sticker” cars drive toll-free in carpool lanes CFL incentive programs Highlight simple steps to save energy in a Home Energy Report Reusable coffee mugs designed not to spill Sophisticated transmission system of hybrid car Compare electricity usage amongst neighbors Hygienic automated faucets also conserve water

13. Work with policy makers and marketers to design thoughtfully structured sustainable product purchase incentives

14. Design sustainable products for ease of use

15. Design product with social norms in-mind

[44]SR, [45]TR

[43]TR

[9]OR, [42]SR

[9]OR, [42]SR

[40]DR [41]SR

[38]BR, [39]BR

[37]OR

Authors’ opinion only – more research needed

[27]SR, [33]TR

[35]DR, [36]DR

[2]SR, [33]TR, [34]SR

[32]OR, [9]OR

[30]TR, [31]SR,

[29]BR, [21]BR

[25]BR, [28]DR

Evidence*

* Design Research (DR), Technology Research (TR), Business Research (BR), Social Science Research (SR), and Research from Other Fields (OR). 4 Copyright © 2012 by ASME

Honda Insight gas tank is smaller to emphasize money saved

12. Change PEB from extrinsic to intrinsic with small, well-timed incentives designed into product interactions

Motivation

Example of what not to do: Monitor home electricity usage that shows a penguin on a melting iceberg

Bank web site resembles the visitors’ cognitive styles leading to increased trust

10. Design trust into the product’s interactions using similarity

11. Avoid making customers feel guilty

Vitra Pantan chair

9. Design trust into the product’s form using semantics and heuristics

Office Equipment/Copy machines

8. Apply design for upgradability or adaptability to work-horse products that are known for reliability and are not status symbols

Vitra Vegetal chair

6. Identify perceptual product cues that communicate sustainability Bamboo resin flooring Cold-water detergent

1 CFL = 10 incandescent light bulbs Poor insulation = A hole with the size of a football in the wall Offer sustainability as the default option

5. Identify useful heuristics and use them to educate about the product’s sustainability

7. Offer only “triumphs” and downplay altruism in the product’s design

Green Mountain biodegradable or reusable K-Cups Example of what not to do: Mercury in CFLs

4. Address the customers’ environmental concerns as well as the crucial sustainability issues

Cognitive Dissonance and Guilt

Trust

Altruism-Sacrifice Link

Decision Heuristics

Energy Star program

2. Constrain customers’ product decisions with industry standards

Complex Decisionmaking Skills

Good example: Energy saving mode on a printer Better example: Select-a-size paper towels Best example: Showerhead fingertip shut-off for shampooing

1. Instill a sense of personal control of the solution by designing products with interactive curtailing features

Responsibility

Examples

Recommendations

Cognitive Concepts

TABLE 1. A summary of cognitive principles, recommendations, related examples and supporting evidence.

performing; thereby feeling empowered to become part of the environmental problem solution. A simple example of a curtailing design modification is select-a-size paper towels (Fig. 3); more perforations on paper towels at smaller intervals mean people can choose to tear off a smaller piece of towel for smaller-sized jobs. An energy saving mode on a printer (Fig. 4) enables the customer to lower their environmental impact by performing a curtailing behavior of energy use. The towel/printer can be sustainably manufactured, providing an efficiency behavior, and offer the customer the opportunity to perform a curtailing behavior. While the energy saving mode button is a start, after the user pushes it once, the interaction is over. A repetitive curtailing behavior is a better approach, as it can build an individual sense of responsibility and control. The towels provide this repetition, but the feature is very basic.

FIGURE 3. Select-a-size paper towel.

FIGURE 4. Energy saving mode on a printer. A more complex example is the Eco-Flow spray shower nozzle from Waterpik, as shown in Fig. 5. Not only does this shower head include an internal valve that increases water force and reduces water usage, a preventative waste measure, it also includes a switch that one can flip to reduce water to a trickle when water is not needed during the shower, for example while shampooing. This interactive waste-reduction feature is especially useful in showers where turning the water back on is difficult, such as in tub showers where the temperature of the water must be adjusted using both hot and cold faucet knobs each time the water is turned on again [46]. As in the example above, this recommendation calls for the use of design methods that identify new ways in which a customer can interact with the product. Saunders et al. find that, in general, design interaction has been shown to be an indication of award-winning and innovative products [47]. While the authors review a few methods for identifying and

improving interactive design features, they call for the introduction of more methods, as does this paper.

FIGURE 5. Waterpik low-flow shower head [46]. Corroborating these suggestions, a recent marketing study [48] emphasizes the vital role of consumers in sustainability agenda by raising a consumer-centric sustainability (CCS) framework and identifying opportunities to facilitate mindful consumption from the four Ps of marketing - product, price, promotion, and place. One implication for designers is that careful design might trigger mindset of caring for self, community, and nature, and thus have potential influence on advancing PEB. Specifically, a product can be designed with attributes that help reduce repetitive consumption, such as being made easier to upgrade and repair, affording use by multiple users, or with attributes that foster responsible consumption, such as providing an option to save energy, and enabling built-in educational feedback. 2.2 Complex decision-making skills The average American citizen has limited understanding of environmental problems and risks [14, 49]. They also have limited understanding of the tools engineers use to try to explain relevant information, including eco-labels and Life Cycle Analysis [50, 51]. The “Reasonable Person Model” suggested by Kaplan [52] asserts that the sensation of being overwhelmed by complexity is a central problem in environmental decisions. It asserts that, because of the way humans evolved, we gravitate towards situations where our information processing capabilities are useful, and avoid situations in which they are not useful. A study by Research International [29] found that too much environmental information led to anxiety and confusion. The research agrees with other findings on cognitive complexity, such as the rule of seven [53] and discussions of simplicity [54]. Following the Reasonable Person Model, if people face a complex and unconstrained sustainable product decision, they may attempt to avoid this decision altogether. They may shift to a commons outlook on responsibility, or, alternatively, restructure the decision for simplification. Restructuring may result in the removal of environmental concerns from their decision, an undesirable outcome from the viewpoint of a designer who has spent much effort creating a sustainable product. For example, a “greenwashed” product that excels only on superficial measures might be selected over a carefully designed sustainable product.

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Yet, people are capable of structuring many complex decisions to include difficult-to-assess, but important, criteria. For example, a car purchase decision remains complex without environmental considerations. It is not that environmental decisions are too complex, but rather that people are not equipped with the mental tools required to address them, such as education, heuristics and trust of information, each to be addressed later. Recommendation 2: Constrain customers’ product decisions with industry standards or regulations. Productcategory-wide sustainability constraints remove some of complexity of the individual customer’s product decision. The Energy Star program is a good example of such a standard that has helped customers to simplify product decisions [55]. This follows the commons/individual duality, in that people do want to make choices that are environmentally significant and beneficial, but that they would prefer if these choices be constrained through political action [21]. However, if a designer would like to present their product as superior on sustainability measures to its competition, an industry-wide standard, such as Energy Star, will not help differentiate products if all available products comply, unless the standard is of a graduated type such as the-less-the-better. Recommendation 3: Encourage tackling of complex decisions through interaction incentives and educational feedback. Incentives can be provided to motivate an individual to tackle a complex decision. Designing small incentives into the product to increase motivation to perform PEB is discussed in Section 2.7. Additionally, monetary incentives may encourage a potential customer to increase the complexity of their usual product purchase decision to include sustainability. Real-time feedback on resources consumed by a product during use is a type of interaction. This feedback can be designed as rewarding to the customer. A comprehensive review of residential sector feedback studies on household electricity use suggests that real-time feedback tends to generate an increase of at least 9% energy savings per household in the past decades [30]. This feedback can help the customer to understand the impact of small behaviors and implications of specific end uses and thus promote PEB. The feedback also can improve the user’s trust of the products claims, increase their motivation to continue performing PEBs, and strengthen their sense of responsibility and resolve for performing PEBs [31, 56]. A good example of rewarding incentives combined with feedback is found in the Toyota Prius dashboard display, which makes fuel savings tangible by displaying information about real-time fuel efficiency and also historical graphics, as shown in Fig. 6. Each image is displayed sequentially when buttons on the steering wheel are pushed. During driving, the Toyota Prius Feedback Display encourages drivers to beat their previous Miles Per Gallon record by learning how to drive more efficiently, and provides a small incentive in the form of a

feeling of reward for reaching a new record, and indicating fuel use reduction.

FIGURE 6. 2010 Toyota Prius Hybrid: Images from instrument cluster [57].

2.3 Decision heuristics Decision heuristics are “shortcuts” that exist in one’s mind in order to simplify judgments and decisions [58]. They are simple, general, efficient rules that develop through experiences and are hard-coded via evolution. Heuristics help people make "fast and frugal" decisions [59] and usually lead to good decision outcomes, but they can also lead to irrational and/or erroneous judgments and decisions. For sustainability, heuristics are not well-calibrated. Several established heuristics have negative implications for sustainable product purchase decisions. For example, consider the popularity of bottled water because it is “healthier” in lieu of addressing the larger problem of the waste produced from the bottles. The public’s concern for specific environment threats is not aligned with the actual risk posed by these environmental threats [32]. One explanation is the availability bias and heuristic: people assess the likelihood of a given event occurring based on the ease of recollection of similar events. Oil spills, nuclear plant accidents, and poisoned drinking water have received much media attention over the past two decades. This attention makes these environmental disasters easier to recall. Thus, people assess the resultant threat to the environment as more likely and possibly more severe than lessexposed environmental problems. Guber reports that poll respondents are much more likely to be worried about air and water pollution—perceptible forms of pollution—rather than global warming, ozone depletion, and deforestation [9]. Logging companies specifically keep strips of trees intact next to highways [2], no doubt in order to prevent travelers from using the availability heuristic to judge the level and impact of deforestation. The affect heuristic causes a person to judge the likelihood of a decision outcome occurring based on the explanation of the outcome—a positively-described outcome is assigned a higher likelihood of occurring than a negative one [60]. Much information on sustainable products is framed negatively, in terms of the product's degrading effects on the environment, and therefore people may think that purchasing the product is unlikely to make a difference.

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“Fast and frugal” heuristics help to quickly assess the sustainability of products. For small purchases, customers may rely on them entirely. For expensive sustainable product purchases, customers will use heuristics confirm their decisions. For example if a hybrid car is shaped like a Hummer, its sustainability will come under suspicion. Some sustainable products take advantage of nascent sustainable product heuristics, such as rough unprocessed-looking fabrics, brown paper, the “recycled” symbol on packaging, matte finishes, and neutral colors. Eco-labels can serve as a heuristic to some extent, but, they are not well recognized, trusted or understood [61]. Recommendation 4: Address the customers’ environmental concerns as well as the crucial sustainability issues. Although customers’ environmental concerns do not always align with the most urgent environmental problems, it is important that engineers and designers not ignore them. If a design solution addresses a fundamental environmental problem but worsens or ignores a less-pressing environmental problem that has a media presence or perceptual availability, the sustainability of the product will be questioned. An excellent example of this problem is carbon fluorescent light bulbs (CFL). CFLs contain a small amount of mercury by design. When a CFL breaks, one can see the mercury fall out of the glass tubing (unless it is released as vapor). Because of the availability heuristic, people think about all of the environmental and health concerns associated with mercury and conclude that CFLs cannot be as good for the environment as they claim. The Environmental Protection Agency (EPA) has a website devoted to debunking this myth [62], explaining that the real concern with mercury is when it is released by the burning of coal in power plants. However, educational discussion is not enough to counteract the strong availability effect. CFLs would achieve further design triumph by addressing customers’ fear of mercury by either excluding it altogether or including a containment mechanism if the bulb happens to break. Considerations from both environmental concerns and customer perceptions are critical to successful sustainable product design. Designers should coordinate complex trade-offs by design, rather than assume that education can retrain previously formed heuristics. Another example is the single-serve coffee market, made popular by the K-Cups offered by Green Mountain coffee and the Keurig line of related coffee-makers. There are environmental advantages to this approach to coffee brewing, such as the reduced use of electricity (do not need to keep a pot of coffee warm all day, do not need to brew more than one will drink), but the waste created is noticeable. Realizing that their customers care about the waste created by using single-serving coffee cartridges, Green Mountain is working to use more biodegradable packaging, recycle the cartridges or make them reusable [63]. Recommendation 5: Identify useful heuristics and use them to educate about the product’s sustainability. The energy-

saving aspects of CFLs were most effectively communicated in American marketing campaigns when the energy usage was compared directly to the status quo, incandescent bulbs, e.g., 1 CLF = 10 incandescent (CFL bulbs last about 10 times longer than incandescent bulbs) [33], thus the incandescent bulb provided the needed heuristic and eco-label. The EPA website mentioned above uses this approach as well [62]: “On average, CFLs contain about four milligrams of mercury sealed within the glass tubing. By comparison, older thermometers contain about 500 milligrams of mercury – an amount equal to the mercury in over 100 CFLs.” Winter cites an effective home energy audit that describes the amount of energy loss through poor insulation as "the equivalent of a hole the size of a football in your living room" [2]. Customers are more likely to choose sustainable or green electricity when it is offered as the default from the utility company [34]—selecting the default is a wellestablished bias in decision-making. Recommendation 6: Identify and use perceptual product cues that communicate sustainability. Sustainability can be expressed through the way the product is perceived. For example, the form of the Vegetal chair by Vitra emphasizes Vitra’s commitment to sustainability with a branch-like design, as shown in Fig. 7 – the chair back is shaped like a lattice of branches. Its plant-like structure evokes nature and sustainability. Vitra has a strong commitment to sustainability and many of its products evoke natural forms [64]. Once a person has made a decision to purchase a sustainable product, they will be more observant of perceptual information that confirms their decision, and less observant of information that goes against their decision, an artifact of confirmation bias [65]. This bias will serve to reinforce sustainability cues in products. This is one explanation for why the Prius’ silhouette is now identified with “environmental friendliness” [35].

FIGURE 7. Vitra veretal chair [66]. Creating designs that communicate sustainability requires the development of new research methods. Related fields of study include emotional design [67, 68], product semantics [69], and such books as Norman’s The Design of Everyday Things [68]. MacDonald has previously identified the crux/sentinel product attribute relationship, where crux attributes are those attributes that are “both important and difficult for people to assess” (e.g., ability of paper towel to absorb water, crash-worthiness of a car) while sentinel

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attributes are those that have “a perceived association with crux attributes but are less complex and often easier to evaluate in product purchase decisions” (e.g., quilt pattern on a paper towel, inclusion of airbags in a car) [70]. The related design method presented can be used to identify other product attribute relationships, such as sustainable product cues. The authors are currently working on investigating design methods to communicate sustainability, and the results show that some perceptual design features can communicate sustainability to the customer [36]. Engineering design methods that identify preferences and sentiments associated with a product’s form [35, 71, 72] can be modified to identify product forms that communicate sustainability. Also, shape-search design methods (i.e. [73]) can be modified to search existing design forms to identify forms associated with sustainability. 2.4 Altruism-Sacrifice Link Researchers have found a relationship between willingness-to-pay for sustainability and altruism [74]. Altruism includes an implicit message of self-sacrifice for the sake of others. Kaplan [52] postulates that “[t]he focus on altruism [in PEB] brings with it the implicit message that living with less will result in an impoverished and joyless future,” and wonders how a sustainable product purchase can be seen to serve both a self-interested and an altruistic purpose. Some people perceive a link, a heuristic, between higher levels of consumption and greater happiness [42]. A sustainable product reduces consumption: people may believe this implies a reduction in product performance. It has been shown that customers are unwilling to make sacrifices on the crucial performance metrics of the product in order to improve sustainability [27]. Early products advertised as eco-friendly or green did offer inferior performance at increased prices, only strengthening this unfortunate heuristic. Consider early CFLs; the light bulbs were only a niche residential product until their design specifications in light color and quality approached or exceeded those of incandescent light bulbs [75, 76]. One of the lessons learned in the American CFL programs was to delay launching products rather than ask customers to sacrifice on core design requirements, as first impressions become strong heuristics and are difficult to overcome [33]. Additional benefits of the bulbs, such as reduced heat and fire hazard, are now highlighted in educational and marketing campaigns. Modern sustainable products must fight the stigma created by their predecessors by consistently offering as-good or better performance than the competition. Recommendation 7: Offer only “triumphs” and downplay altruism in the product’s design. Use extreme caution when including a message of altruism in the product’s design or marketing campaign, as the customer could infer that the product is inferior to the competition. A sustainable product should create demand through design benefits to the customer—it should be a triumph, offering performance equal to or better than competing products and extra features. Some sustainable design tools try to consider the needs from

environmental as well as traditional quality points of view, such as House of Ecology [77], Quality Function Deployment for Environment [78] and Function Impact Matrix [79, 80], which confirm that environmental improvements could be made without affecting functional performance. Fitzgerald et al. [81] offers a conceptual design tool that helps designers to resolve functionality-environmental contradictions about the product design, and move the products to the direction of being desired by customers and also excelling from an environmental standpoint. Including luxurious finishes or indulgent design features (while minding product perception) may negate feelings of altruism and sacrifice associated with buying a sustainable product. Warranties, free-samples, and/or trial periods will help to alleviate performance doubts. An example of a sustainable product that has transcended the altruism-sacrifice heuristic is bamboo resin flooring. The flooring has been positioned in the market as modern, durable, and affordable. One brand, Ecotimber, was rated the best in the category of prefinished floors, up against standards such as oak and maple [82]. The sustainability is sold as a bonus feature, second to the price, durability and modern appearance. The sustainability features include VOC-free, non-toxic adhesive as well as renewable bamboo. Coldwater laundry detergents, which can save threequarters of the energy use [83], have been available for several years, but customers are “just skeptical that normal dirt and spots can be washed out with cooler water” and “manufacturers have discovered that coldwater washing is such a hard sell that they have relegated claims about it - and the attendant green benefits - to the fine print, choosing to emphasize other attributes” [83]. Efforts to downplay this altruism-sacrifice link are evident in Tide’s detergent bottle. Fig. 8 shows an old Tide Coldwater detergent bottle (on the left) and a current bottle (on the right). The old one emphasizes its environmental benefit with the green cap design and “nature” labeling. The current Coldwater bottle looks very similar to the rest of the detergents in Tide’s product line. It first reassures customers of the product’s efficacy by the bottle design and energy saving is just an “attendant”, marketed as “Brilliant Clean at Lower Temperatures”.

FIGURE 8. Coldwater detergent bottles. This revamp of Tide’s Coldwater bottle exhibits an important point. The approach taken is in contradiction to Recommendation 7: Identify and use perceptual product cues to indicate sustainability. According to Recommendation 6, the

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bottle on the left in Fig. 8 should be the more successful product. However, because of the strength of the feeling of performance sacrifice for “green” detergents, it is necessary to downplay this attribute in the product’s packaging. Not all recommendations will work for all products. Recommendation 8: Apply design for upgradability or adaptability to work-horse products that are known for reliability and are not status symbols. There are a number of sustainable design methods that allow products to be upgraded or adapted to include new features [84, 85]. Xerox makes upgradable office equipment, such as allowing lower version digital copiers to upgrade to a fully networked system. Copiers are an excellent example of a winning upgradeability approach – it is a product category where customers are looking to save money and maximize the useful lifetime of a single product purchase. However, products that are associated with status, such as cell phones or automobiles, or brands with negative reliability stereotypes, such as some printer and automobile brands, must proceed with caution in refurbishment or reuse design strategies. In these special circumstances, designers must be aware of the power of “new” versus “used” in terms of sacrifice and consumption. The customer will likely blame any product failure on the supposed inferiority of reused parts, no matter the cause, due to the altruism/consumption-sacrifice heuristic. The methods mentioned above are both flexible in their incorporation of design constraints, and constraints on user perceptions of reused parts should be included. Notably, Recommendation 8 is the only recommendation included without citation evidence from within the design field or without. The authors chose to include as their own recommendation based on their extensive research on the altruism-sacrifice link. More research is needed to corroborate the authors’ opinion. 2.5 Trust To navigate the above cognitive concepts while actively searching for a sustainable product, a person must trust (a) the science that supports the environmental problems, (b) his or her ability to personally affect the problems with PEB; (c) the sustainability claims made by products; and (d) the up-to-par performance of the sustainable product. It may seem reasonable that a person would seek expert advice to aid their search; however, experts from the environmental movement are not fully trusted by the public. In her analysis of the results of a number of polls, Guber [9] came to the conclusion that “[b]y downplaying environmental progress and using exaggerated doomsday warnings to motivate public awareness and concern, the environmental movement has sacrificed its own credibility by giving into the politics of Chicken Little.” Eco-labels and environmental marketing messages are also not trusted by customers [50, 86, 87]. Eco-labels on products or product packaging are a form of “direct persuasion” advertising, information provided by the products’ manufacturer. Even if the environmental information is accurate and helpful in the purchase decision, customers will

think that the change in purchase habit is in the best interest of the persuader (and perhaps not in their own best interest). Women who are more likely to buy sustainable products are also more likely to find advertising insulting [86]. Direct persuasion advertising may also shift responsibility for the behavior, leading customers to think that ultimate blame for consequences of their environmental decisions rests on another party, namely, the persuader [42]. This is not to say that all eco-labels are useless and do more harm than good, but it is important for designers to note that eco-labels do have drawbacks and are ineffective as the sole conveyance of product sustainability. It is often difficult for customers, and other stakeholders to ascertain the extent to which a firm’s products and processes are sustainable [88]. The firm may have an incentive to deceive on marketing messages, otherwise known as “green washing”, if they wish to appear more committed to sustainable practices than they actually are. Therefore, costly mechanisms such as ISO 14000 certification [89] and investment in sustainable technologies are all examples of signals that can communicate a commitment to sustainability to various stakeholders [90]. For example, considerable investment in a grass roof for a manufacturing plant may make more sense than an eco-labeling program as it is highly observable and costly to imitate [90]. Green Mountain Coffee installed a “huge solar array on the roof of its distribution center” last year [63].

FIGURE 9. Vitra Panton Chair [91]. Recommendation 9: Design trust into the product’s form using semantics and heuristics. Industrial designers have been taught to evoke trust in an object’s form. They utilize the theory and analysis of design semantics [69] to create a perceptible sense of trust in the visual lines of the product. Establishing “trustworthy” heuristics, for example using the abovementioned crux/sentinel attribute identification method [70], will help customers identify sustainable products and reinforce their decision-making approach such that specific forms will become heuristics in future product purchases. The Vitra Panton chair (Fig. 9) distributes load and stress through one single cohesive form. Although the form is unusual, the robust cantilever base reassures customers that they will not tip over. The strong silhouette of the side of a chair is also included in the design, to give trust through a recognizable chair-shape. Wang and Emurian [37] discuss fourteen trust-inducing interface design features that may influence a user’s perception

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of the trustworthiness of an online merchant’s web site. These features are highly correlated with the heuristics people often use to judge credibility, such as well-chosen and good-shot photographs, and relevant domain name—extending such research to product design will require more research. Recommendation 10: Design trust into the product’s interactions using similarity. If a product has a computer interface, a number of studies suggest that the product is considered more trustworthy and persuasive if the interface resembles the user [56]. “Resembles” can refer to the cognitive style in which the information is presented, i.e. visual or verbal [38], or other personality traits, physical traits, or affiliations that resemble the customer [56]. In [39], a study of selling credit card loans on a Web site, people are shown to be more likely to trust a Web site when it resembles the visitors’ cognitive style (analytical vs. impulsive, for example).With further research, it may be possible to use the finding for product design. Cognitive-style dimensions related to design could be, for example, flexible vs. inflexible, innovator vs. traditionalist. 2.6 Cognitive Dissonance and Guilt When an individual performs a behavior with the intent of reducing environmental impact, but later realizes that the behavior is detrimental to the environment, they will experience cognitive dissonance, a mismatch between cognition and action, or value and behavior. They will have a strong need to resolve the mismatch [92]. Changing behavior to match their values resolves the dissonance, so triggering cognitive dissonance can motivate the performance of PEB. For example, a door-to-door campaign in which subjects agreed to send a personal pro-recycling postcard to a friend increased the recycling activities of the subject [2]. Behavior changed to match the intentions the subjects expressed in the postcards. When spillover between pro-environmental behaviors occurs, it may be a resolution of cognitive dissonance; in essence, if you behave sustainably during one activity, all your behaviors must improve in sustainability in order to be consistent. However, people can also resolve cognitive dissonance by changing cognition to match behavior [13, 93]. People can change their values, attitudes, or beliefs about the environment to a position of less concern. Note that resolving cognitive dissonance in this manner for one behavior will affect all other behaviors—the person may fundamentally decrease the importance they place on environmental problems, or their belief that environmental problems exist. A customer may change their decisions about the sustainable products they currently buy. Therefore, attempting to motivate PEB by intentionally triggering cognitive dissonance is not advised. People can experience feelings of guilt about negative environmental impacts if they have formed an individualized sense of responsibility, listened to the “shame and blame” tactics of the early environmental movement, or experienced unresolved cognitive dissonance regarding the products they buy. In motivating pro-environmental behavior, researchers

stressed that inducing feelings of guilt should be avoided, as guilt can cause a change in behavior, but it can also cause a disguise or denial of the target behavior [29]. One researcher who implemented a recycling program noted that a man who chose not to participate in the program saw his neighbors’ recycling buckets waiting for pickup and decided to put some of their recycling into his bucket—an entertaining example of a disguise of target behavior [13]. Recommendation 11: Avoid making customers feel guilty. Be cautious of product interactions that trigger guilt or cognitive dissonance. Work with marketers to remove these concepts from marketing campaigns. Emphasize responsibility and control for solving the problem, not for causing it. As mentioned in Section 2.1, the majority of individuals believe that the industry is already working to promote sustainability. Before introducing a new sustainable product, it is important to study the customers’ impressions of the sustainability of current product offerings. If they believe the current products are sustainable, introducing a new sustainable product may cause them to feel cognitive dissonance about the product they currently purchase. Avoid this situation by separating the two products so they are not directly compared, using features, pricing, and branding. Be careful of product interfaces that induce guilt. At a recent sustainable design workshop, an electronics company displayed a prototype interface for monitoring home electricity usage that showed a penguin on an iceberg. The iceberg melted and eventually disappeared if the homeowner used too much electricity. This type of interface should be avoided because it will trigger guilt and may result in customers changing their level of concern for the environment. Interfaces such as these should highlight accomplishments and not shortcomings. This is consistent with Lilley’s recommendation for the design of sustainable devices. Lilley explored the design strategies for changing mobile phone user behaviors in public and investigated the acceptability and effectiveness of these potential strategies with design professionals. The interviewed design professionals agreed that “in order to be accepted, the product would need to support, not contradict, user’s values” which led to her recommendation to “Use predominately positive, rather than negative reinforcements” when trying to change user behavior [40]. Flora discusses behavior change in general, not just related to sustainability, and concludes positive reinforcement is more effective than criticism overall [41]. Praising pro-environmental behavior will facilitate learning and positive motivation better than criticism of behaviors with damaging environmental impact [42]. 2.7 Motivation Applied behavior analysis is a sub-field of psychology that researches how to motivate change in behavior. Vining and Ebreo [13] review the three types of behavior motivation: (1) intrinsic motivation, in which a person derives satisfaction from performing the behavior; (2) extrinsic motivation, in which

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person derives satisfaction from a reward given when the behavior is performed; and (3) a motivation, in which a person receives no satisfaction from the behavior, and is unsure why they are performing the behavior. One could expect that a personal norm or feeling of moral obligation provides a strong intrinsic motivation for PEB, but this is not always the case [94]. People are most likely to participate in PEB through extrinsic motivation: when there is a tangible incentive and personal sacrifice is slight [9]. Financial incentives are extrinsic motivators. Guilt and/or cognitive dissonance are examples of extrinsic motivators—correcting behavior gives the reward of the removal of an unpleasant cognitive state, but as discussed they can lead to unwanted consequences. The applied behavior analysis literature directed at promoting PEB indicates that specific extrinsic motivators must be tailored to the desired behavior change. Sustainable product purchase decisions are best motivated with incentives that are short-term, repetitive, and small in size: “[r]eward schedules that are just sufficient to initiate behavior change are more likely to produce longer-term behavior change than more powerful rewards” [42]. The reason for this is that people attribute the reason for behavior change based on the relevant circumstances and the size of the reward. A large, one-time incentive to motivate PEB causes a person to attribute the behavior to the efforts of the one providing the incentive. Small, repetitive incentives cause a person to eventually attribute the behavior to their own volition, thus shifting from extrinsic to intrinsically-motivated PEB [42]. This transition is important to achieving repeat sustainable product purchases and effective use. Note that addressing the environmental tragedy of the commons, offers only long-term and subtle results; naturally-occurring short term rewards are sparse. Recommendation 12: Change PEB from extrinsic to intrinsic with small, well-timed incentives designed into product interactions. Sustainable products that have long-term environmental impact reduction goals can be designed to include features that provide near-term benefits, such as including fair trade or locally-produced materials [94]. Delight in product features can also be considered a short-term incentive. Design methods that discover delighting product attributes can be used to investigate what attributes can provide short-term incentives via product use [88, 95]. The proper spacing of incentives to achieve the transition from extrinsic to intrinsic motivation requires design creativity. Smaller and more fuel-efficient hybrid cars like the Honda Insight are fitted with smaller gas tanks. Due to the high MPG, the driver might fill the tank as often as other car drivers, but buys less gasoline, i.e. 10 gallons. The driver is delighted by needing to pay less for gas and driving the same distance, an incentive that is received every time he or she fills the tank. Honda could have designed the Insight with tank similar to non-hybrid cars, and instead of having cheaper fill-ups allow customers to drive further in between fill-ups. But, in this case, the drive would not receive this same feeling of delight. It is likely he or she would not notice the change in fill-up

frequency as vividly as the change in the cost of gas per tank, and would not feel the same sense of reward. A nightclub in Netherlands uses a new type of dance floor that harvests the energy generated by jumps and gyrations and transforms it into electricity to supply the energy need of the whole club. The dance floor, which functions through piezoelectricity technology, motivates customers’ PEB with enjoyment [96]. Recommendation 13: Work with policy makers and marketers to design thoughtfully-structured sustainable product purchase incentives. An example of a good incentive for transitioning from extrinsically to intrinsically motivated PEB is California’s “Clean Air Sticker” program [97]. California issued eighty-five thousand clean air stickers to hybrid and low-emission vehicles that allowed the driver to use carpool lanes with only one passenger in the vehicle. Every time the owner drives the vehicle, they receive a small incentive: a faster commute time and savings of $2.00 to $4.00 if they are crossing a toll. The vehicles with stickers have also retained a higher resale value. A large, one-time financial incentive in the form of a rebate on a new car purchase (i.e. the U.S. “Cash for Clunkers” program) is unlikely to spur future PEB [98]. Public policy has played a crucial role in developing CFLs from a niche lighting product into a mass product in the residential market [33, 75]. A variety of incentive and educational programs have been used in different countries to encourage adoption [76]. However, no country made the transition to CFLs by passing a law that mandated all light bulbs for sale in the residential market be CFLs, or at the other extreme, only putting the bulbs on the shelves in retail stores and waiting for customers to purchase them based on economic merits alone. Governments and manufacturers introduced CFLs through policies that encourage their use on an elective basis by individuals. When CFLs are widely adopted, stricter use laws can be instated, such as California’s Title 24 Residential Lighting Building Code that imposes strict efficiency requirements on built-in lighting fixtures [99]. Policy-makers benefit from motivating individuals to perform pro-environmental behavior [7]. Sustainable technologies are more cost-effective and faster to implement when individuals are willing to accept the technologies and even demand them. The coordination of perspectives is recognized as important—there is now a bill under consideration in the U.S. Senate to add a social and behavioral science office to the Department of Energy [100]. The impact of policy on design decisions has been explored in the literature (i.e. [101, 102]). Recommendation 14: Design sustainable products for ease of use. A rationale that people frequently give for not performing pro-environmental behaviors is that they are hard to do [14]. One study demonstrated that perceived behavior barriers to transportation (e.g., low frequency of public transport, transfers necessary with public transport, reduced time budget) are closely associated with increased automobile

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driving frequency [43]. At a recent webcast offered by Department of Energy, Gainesville Regional Utilities (GRU) with Opower reported their success of a Home Energy Reporting Program, where simple steps to save energy are always highlighted [103], e.g., weatherization and sealing and using CFL bulbs. These tips are easy to follow and thus prompt people to be more likely engaged with their energy-savings. Sustainable products should be easy to use and understand. Product heuristics, or emotional design, that read as "easy" or "simple" can be built into design features to provide further encouragement. Some examples include: perforations on selecta-size paper towels (Fig. 3); spill-proof reusable coffee mugs; and sophisticated hybrid transmission systems that simplify the process of shifting and sharing power among the engine, electric motors and wheels—with no special driving techniques required. Recommendation 15: Design product with social norms inmind. Normative social influence has a powerful effect on behavior, especially in defining what constitutes correct behavior—“We view a behavior as correct in a given situation to the degree that we see others performing it” [104]. That explains why infomercials always demonstrate people from various walks of life happily buying and using the advertised products. An experiment [44] studied what motivated people to save energy by placing door-hangers containing different persuasive appeals around a mid-size Californian community. The appeals emphasized to residents that turning off an air conditioner and turning on fan: (1) saves money; (2) helps the environment; or (3) benefits society; or (4) is a common practice in their neighborhood (appealing to social norms). Upon examining the actual energy usage, the social-norms appeal has significantly higher impact on reducing energy consumption [44]. Gainesville Regional Utilities (GRU) with Opower employed social norms in conjunction with its innovative home energy reports by comparing residential utility customers’ electricity use to that of their neighbors [105]. In sustainable product design, designers are challenged to take social norms into consideration and encouraged to go out and watch people in their normal environment to find what they believe and do [106]. Automated faucets provide the convenience of hands-free on/off activation and help to conserve water. The normative value embedded into the automation technology, a more automated faucet is also a more hygienic one, motivates customers to use the product, and repeated use shapes their behaviors [45]. 3 CONCLUSION Compiling diverse research findings from a broad disciplinary scope, we converge on seven cognitive concepts that are important to consider in consumer-driven design, namely: responsibility, complex decision-making skills, decision heuristics, the altruism-sacrifice link, trust, cognitive dissonance/guilt, and motivation. These are summarized with examples and supporting evidence in Table 1, Section 1, and shown illustratively in Fig. 10.

Recommendations 2-5, 7-10, and 12-15 are not evidenced by design research but instead by research and opinions from publications outside the design community. Recommendation 8 is noted as the authors’ own opinion only. These recommendations are beneficial as a starting point to inspire designers on sustainable design from a multi-perspective view, but further work is needed to validate them in design research.

FIGURE 10. Sustainable design recommendations derived from the seven cognitive concepts.

The concepts have implications when used in conjunction with some concept-generation design methods that focus on understanding the customer perspective. For example, a study of these concepts during conceptual design would work well in conjunction with an empathic design approach [107], as it is important to feel and experience as the target customer with respect to the seven concepts. Sustainable design paired with a lead user approach [108] may yield dissatisfactory results. Lead users are at the forefront of the market demand, and, for sustainable product demand, likely to be well-versed in sustainability evaluation and willing to sacrifice functionality for the benefit of the environment. A better approach might be to target “lag users,” for example, someone particularly frustrated with understanding information about sustainable products, or someone who has had negative experiences with many sustainable products in the past and stopped using them. Design decision literature has many methods to offer for addressing this multi-pronged, multi-perspective design problem (i.e. [109-111]). A systems and interdisciplinary perspective is recommended for both addressing and teaching

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sustainability in the literature, and the findings here further emphasize the importance of this approach [112-114]. The recommendations also highlight the need for new design methods that treat customers not as a static source of design criteria, but as dynamic and interactive members of a larger social system. Customers’ preferences and assessments of sustainable products will change as their behaviors change. The manner in which customers use products to curtail environmental impacts and the heuristics customers form to help them judge the sustainability of products will change over time. Quantitative methods are needed to affect these changes, specifically in developing product interactions, influencing product heuristics, and designing motivational incentives. Future sustainable design studies must focus on achieving positive change in individuals’ behaviors using a combination of approaches. The recommendations above require coordination between designers, manufacturers, marketers, and government policy-makers. The success of sustainable products depends on the success of this coordination. ACKNOWLEDGMENTS This work was partially supported by a National Science Foundation Graduate Research Fellowship, the Donald C. Graham Chair Endowment at the University of Michigan, the University of Michigan Rackham Graduate School, and the 2050 Mack Challenge Scholar program at Iowa State University. REFERENCES [1] Gifford, R., 2007, "Environmental Psychology and Sustainable Development: Expansion, Maturation, and Challenges," Journal of Social Issues, 63(1), pp. 199-212. [2] Winter, D. D. N., 2000, "Some Big Ideas for Some Big Problems," American Psychologist, 55(5), pp. 516-522. [3] McKenzie-Mohr, D., 2000, "Fostering Sustainable Behavior Through Community-Based Social Marketing," The American psychologist, 55(5), pp. 531-537. [4] Peattie, K., and Charteris, W., 2008, "Green Marketing," The Marketing Book, M. Baker, and S. Hart, eds., Oxford. [5] M. Hult, ed., 2011, The Journal of the Academy of Marketing Science, 39(1), Springer. [6] Slovic, P., 1995, "The Construction of Preference," American Psychologist, 50(5), pp. 364-371. [7] Jackson, T., 2005, "Motivating Sustainable Consumption, Center for Environmental Strategy," University of Surrey, http://www.sd-research.org.uk/wpcontent/uploads/motivatingscfinal_000.pdf, Accessed 1/9/2012. [8] Ramani, K., Ramanujan, D., Bernstein, W. Z., Zhao, F., Sutherland, J., Handwerker, C., Choi, J. K., Kim, H., and Thurston, D., 2010, "Integrated Sustainable Life Cycle Design: A Review," Journal of Mechanical Design, 132(9), p. 091004. [9] Guber, D. L., 2003, The Grassroots of a Green Revolution : Polling America on the Environment, MIT Press, Cambridge, Mass.

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