There's a difference between green engineering and green design.

Green engineering reduces people's ecological impact without requiring them to change their habits--for instance, replacing coal power with wind power; the consumer still just flicks the light switch, and their lights turn on just the same.

Green design reduces people's ecological impact by changing their habits--for instance, better urban design lets people walk to work rather than driving to work. Everything has a user interface, even cities. How easy is it to find transit, how close does it go to where you want and when you want? Is there a corner store a block away, or just a big-box store five miles away?Both green engineering and green design are vital for creating the bright green future of sustainability, prosperity, and health that we all want. Green engineering is much better understood than green design, so let's push the green design conversation forward a bit. One strategy for it that's powerful -- but almost wholly unused -- is persuasive design.

Persuasion is a science; newborn and inexact, but a science nonetheless. Advertisers and marketers know this; designers should, too. Persuasive design is not marketing or advertising, it is crafting a product's user experience so that the user's actual interaction with the product changes their behavior. Stanford lecturer and researcher BJ Fogg invented the field of study, with two books on the subject (the first simply called Persuasive Technology and the other focusing on Mobile Persuasion). So far those are the only must-read resources on the subject, but the field is rapidly growing, and the fourth annual Conference on Persuasive Technology is happening at the end of this month in Claremont, California. Proceeds from the previous conferences can be bought, though they are expensive.

Fogg has isolated over a dozen principles of persuasion, and grouped them into three main avenues: tools, media, and social actors. Each of them apply more to some kinds of products than others would, and since he is primarily a computer scientist, they are weighted heavily towards software and electronics. We need more physical-product designers in this field. Here are most of the strategies, in a nutshell:

Persuasive Tools

Tools seem objective, but they're not. A hammer makes you want to pound things, while a screwdriver doesn't, because that's what the hammer was designed for. Here are the ways that tools can persuade:

- Make a behavior easier or more convenient. This can mean doing work for you, such as Google Transit figuring out what buses you should take to get from point A to point B, something that can take hours of sifting through paper schedules and route maps to figure out. It can also mean defaults or shortcuts, like laptops that come with energy-saving sleep functions turned on; most people never bother changing defaults. Finally, it can mean leading the user through the process when you want to encourage behavior that's complicated, multi-step, or otherwise daunting to the first-timer. Again using Google Transit, it doesn't just tell you what routes to take, it lists everything step-by-step, telling you to walk to a certain bus stop, get on a certain bus, get off at another stop and walk to the train station, etc., flagging each mode change with colors and icons, both on the map and in a list.

- Calculate / simulate / measure. It's one thing to say, "global warming is a risk." It's another thing to say, "an atmospheric CO2 level of 450ppm will cause sea level to rise 1 - 3 meters." The latter argument is not only more credible, but it is specific and actionable, and tells you the consequences of inaction. There are even multiple Google Maps applets that will simulate this world, showing you what a 1m (or 3m, or 20m) sea level rise would do to the place you live. (Just zoom out to find your home.) There are a slew of carbon footprint calculators, life cycle analysis programs, and other tools to help you quantify your impacts. Many of these tools (like LCA) even help you compare the impacts of different strategies, so you can make more intelligent design decisions and know your priorities better.

- Give feedback. Nobody wakes up wanting to despoil the Earth; but heretofore product interfaces have hidden all the scary ugly environmental impacts from us. That helps us sleep easier, but it doesn't help us make informed decisions. Knowing how products are performing in real time can make a big difference in people's impacts. The best-known example of this is the Prius mileage screen: just seeing how many miles per gallon they get in real time causes people to drive more fuel-efficiently.

Persuasive Media

Media tells a story, and any product with a screen or a speaker can act like media; all packaging can act like media, too. As such your devices and packages can utilize all the tricks of the advertising and marketing trades. Here are the main ways media can persuade:

- Cause-and-effect simulations. Letting users try different choices and see the different outcomes can be very motivating. A robot pet like a Tamagotchi can train a user to feed and care for it properly by appearing happy, sad, or sick at the right times. With simple print media, the book 1984 took real socio-political forces and extended them into a possible future so vivid it has influenced politics for decades.

- Rehearse behavior. Performing actions in a virtual world or with a physical product get the user accustomed to performing those actions, which is one of the most powerful techniques of persuasion. Even without cause-and-effect simulation, a videogame where turning out lights gets you points will train you to remember to turn out lights in real life.

- Environment simulations. Virtual worlds can train people to go beyond their normal comfort zones, either by making activities more fun or interesting, or making them safer. If exercising on a stationary bicycle is boring, it can be juiced up by getting to explore a virtual terrain while pedaling. As the videogame industry knows well, an environment that would be overwhelming or dangerous in real life can be harmless, and even quite fun, in a virtual world where no real harm can come to you, or where you can pause and step out of the world when it is too much. The game "A Force More Powerful" trains players to overthrow oppressive governments through peaceful opposition, an activity quite frightening and dangerous in the real world.

- Telling the backstory. This one is not part of Fogg's book, but is an important point for sustainable products and packaging. The products on the shelf in the store are anonymous as strangers on the street. Where did they come from? Who made them, and how well were the workers treated? How much energy, water, and materials were used to make them? How much waste and toxicity did they produce, and how much will they produce in your home? How long will they live? If we knew the story of all the products on the shelf, many people's buying habits would instantly change. Some people are pushing the creation of detailed eco-labels to make the backstory told more.

Persuasive Social Actors

Both real and imagined social actors can be persuasive--persuasive technology can leverage the persuasiveness of real people by multiplying their outreach, and products themselves can behave as social actors. People personify many of the products in their lives. Does your car have a name? Is your computer cranky, or well-behaved? Even when we know objects to be simple conglomerations of steel and plastic and electronics, we still tend to imbue them with personalities. We react to them not as if they were fully human, but as if they had some character and "elan vital"--as if they were social actors. Here are the ways social actors can persuade:

- Rewards / punishments. This is the most obvious persuasive interaction, straight out of behavioral psychology. If alarm klaxons went off every time you left a room without turning off the lights, you'd quickly learn to always turn them off, and save energy through better habits. More realistically, many software tools that involve long complicated procedures (Such as TurboTax or many install wizards) will give users a "Congratulations!" at the end to make them feel better about having gone through the process.

- Liking / attractiveness. Attractive people don't need interesting personalities for people to want to hang around them; likewise, attractive products don't have to perform that well for people to want to use them. This has been the cause of decades of frivolous garbage in the ID world, but it can also be leveraged to promote sustainable products. One of the reasons the second-generation green wave is stronger than the first is that it is aesthetically slick and polished rather than being a hairshirt. Many green products have become aspirational, rather than embarrassments.

- Reciprocity. One of the most fundamental and universal human values is that if you do something nice for me, I should do something nice for you. A product that performs better for a user can get the user to do more for it (perhaps maintenance and upgrades, or data collection, or other environmentally beneficial actions). This can be used to extend product life or change user habits.

- Nagging. Gentle but persistent, reminders to take a certain action can be very effective. Nearly all shareware software uses nagging to get users to pay for it. However, nagging can get annoying rapidly, so it is important not to overuse.

- Modeling a behavior / attitude. Seeing someone else behave a certain way, or propound a certain outlook, can convince people to behave or think that way. This is by far the most effective with social actors whom your users are attracted to or identify with (including aspirational attraction and identification). Countless nonprofits and political activist groups use technology such as email, websites, twitter, and text messages to leverage the modeling actions and attitudes of a few people in writing their senators, voting a certain way, or boycotting certain products.

- Social support. People are more confident and comfortable behaving or thinking in ways that they know are shared by others. Having a community also helps people work out the bugs in their own pursuits by asking questions or having discussions. Every application with "Web 2.0" functionality--WiserEarth, Ask Nature, even this news site--leverages real people's social support by connecting them together.

Levels & Locations of Persuasion

Persuasion can happen on different levels, as well. Fogg divides things into two levels: "macrosuasion" and "microsuasion". Macrosuasion is when the sole purpose of the device or website or whatnot is to persuade you. (He uses the example of Quitnet, a website dedicated to helping people stop smoking.) But sometimes subtler persuasion can be even more effective. Microsuasion is when the persuasive feature is a small part of a larger product or software. (For instance, in Google Maps, you can click a button to get transit directions or walking directions, instead of driving directions. Originally Google Transit had its own separate page, but it is used and viewed by far more people as a button on an already-popular tool than it ever was or would be as a separate site. As a result, it persuades more people to take public transit even though it's a less dominant tool.)

Persuasive design in mobile devices can be especially powerful, because it can present you with exactly the right information or suggestion at exactly the right time and place for it to be most relevant and actionable. For instance, the transit function in Google Maps on the iPhone lets you find a bus route to your destination without you even having to know where you are, just using the phone's built-in GPS to find you and tell you where the nearest or soonest bus will be. Armed with this knowledge, you know you don't have to drive or use a taxi to get back home reliably, and in the process of using it you start to learn the local transit lines most relevant to you, so eventually you won't even need the tool for common trips.

Persuasive Design for Sustainability

Persuasive design can be an extremely powerful tool in the green designer's tool belt. It shouldn't be the only tool, certainly, but it can do things impossible for engineering, and can also complement green engineering that requires new habits or heightened awareness from the user. Persuasive technology isn't inherently green--in fact, we are already living in a world with design biases that push our behavior towards overconsumption, irresponsibility, and shortsightedness. We need to short circuit those existing persuasions, and steer users in the right direction. Knowing how objects persuade can help us do this, and using persuasive strategies can encourage more sustainable user habits in everything from building design to transportation design, from computers to coffee makers to clothing.

One last thing to consider about persuasive design is the ethics of the tactics you use, and the agendas which your persuasion promotes. Use your super-powers only for good. There can be a fine line between making things convenient and making things constrictive, or between educating the user with knowledge and manipulating them with propaganda. In our efforts to create a brighter greener future, we have to remember the means are as important as the ends, because by the definition of sustainable design, better means are the ends we seek.

image credit: Amazon.com