We introduce the 4Ps Framework for Behavior Change as a broad strategy for nudging behavior toward desirable outcomes in specific situations—such as making healthy food choices. Whereas the rich and growing nudge literature offers a cornucopia of unrelated manipulations for effecting behavioral change, the 4Ps—Possibilities, Process, Persuasion, and Person—bring this research together in a framework to facilitate new ideas for both researchers and policy makers. The nudges fall into four broad categories: what choices are offered (Possibilities), how choices are made (Process), how choices are communicated (Persuasion), and how intentions are reinforced (Person). (See Fig. 1 for a summary of the framework.) Below, we discuss the 4Ps and present examples of research findings and types of interventions that fall into each.
“Possibilities” refers to the available options, or composition of the choice set, including the assortment that is offered (items and attributes), how much is offered (quantity), the arrangement (variety and bundles), and changes in the assortment over time. Interventions within Possibilities nudge people toward healthy choices either by making specific options healthier, or by changing the relative attractiveness of the options to advantage healthier ones.
Research shows that mere availability has a strong impact on consumption: people tend to eat whatever is in front of them. In a study of children’s eating habits, availability was the number one driver of consumption of fresh fruits and vegetables . The consumption of convenience foods such as crackers, granola bars, and juice similarly increases when families stockpile them, making those foods more available . In the domain of assortments, one study found that people are more likely to choose a healthy option (a fruit over a cookie) from a larger assortment than a smaller one . Sometimes, options that are already available can be made healthier (e.g., switching from white to whole-grain pasta), or more appealing. In one study, placing fruit in a nice bowl or under a light increased fruit sales by over 100 % .
After the choice set has been determined, the planner must decide how much of each item to offer—how large should the package or portion be? Quantity discounts (supersized pricing) can increase the amount consumed , due to a “unit bias” : people tend to believe the appropriate amount to eat is an entire portion (e.g., plate, bowl, or package). As a result, they serve themselves more and eat more when dishes or utensils are large. In one experiment, nutrition academics at an ice cream social served themselves 31 % more ice cream when given larger bowls and 57 % more when given both larger bowls and larger serving spoons . People also pour and drink more from short, wide glasses than tall, thin ones: children poured 70 % more juice, and experienced bartenders poured 37 % more alcohol into a short, wide glass of the same volume as a tall, thin one .
Not only the options themselves, but also the variety of an assortment impacts the attractiveness of different options, and in turn, their consumption . While people are more likely to choose a healthy option when there is greater variety of them , even mere perceptions of variety affect satiation. People satiate faster if a meal has less variety or if they perceive a consumption experience as less varied . Kahn and Wansink  found people ate fewer M&Ms when a bowl contained fewer colors of them, even though all colors of M&Ms have the same flavor.
In many cases, healthy and unhealthy options may be consumed simultaneously, and creative bundling can nudge people toward health. Bundling a healthy salad with a small portion of fries to create a “vice-virtue” bundle can persuade some people who would have ordered fries instead of salad to choose a bundle of one fourth fries and three fourths salad . Vice-virtue bundles have nudged people to exercise as well—in a field study, Milkman et al.  encouraged people to exercise more by allowing them to listen to tempting audiobooks only while at the gym.
We have shared a number of possibilities for steering people toward healthy choices by modifying the composition of the assortment itself. Once a planner selects the assortment, he or she can then decide how to structure the choice, or how to position the possibilities in physical space. These decisions impact the choice process, to which we turn next.
Process interventions influence behavior through changing the position of options in physical or psychological space, affecting the items’ relative appeal or relative ease of selection. Process interventions can change the physical location of the options (accessibility and order) or the structure of the choice (defaults). Because they involve changes to the context in which a person makes a choice, behavioral economists call Process interventions “choice architecture” .
Accessibility, or convenience, exerts a gentle yet powerful influence on choices. A long-term field study in a hospital cafeteria showed that making water more accessible by placing it at eye-level in refrigerators and in five baskets located near food stations increased water consumption by 26 % . People also drink more water when it is easily accessible on their table, rather than 20 ft away . Conversely, cafeteria visitors purchased fewer junk foods when they were less accessible, requiring waiting in a separate line , and in another study, people were less likely to serve themselves ice cream when it was less accessible, in a closed rather than an open freezer .
Order, too influences choice outcomes. Different positions are privileged in different contexts, but overall, privilege is determined by ease: choice shares are higher for options which are easiest to reach, remember, see, or rationalize. At a conference breakfast, the same seven dishes were served in two buffet lines, ordered either from healthiest to least healthy or vice-versa. Conference participants randomly assigned to one of the two lines filled two thirds of their plate with the first three dishes. As a result, those who reached the healthy items first served themselves more fruit and yogurt—and less cheesy eggs, bacon, and fried potatoes . Similarly, children in a school cafeteria took more vegetables when the vegetables were placed at the front of the line . Being first on a list helps too: featuring healthier sandwiches prominently on the first page of a menu can increase choice share . In a set of three options, the middle item holds the privileged spot. When options are ordered by an alignable attribute such as size, people with weak preferences tend to compromise by choosing the middle option because it is easier to rationalize .
A final technique for influencing the choice process is through defaults . Due to the powerful and pervasive bias toward the status quo , defaults have proven extremely effective in guiding choices even in domains as weighty as organ donations  and retirement savings , as well as food choices. In one study at a Chinese takeout restaurant, patrons were asked whether they would prefer a half-serving of rice (thereby cutting 200 cal out of their meal) without receiving a price discount. A quarter of all customers chose this option, which had always been available, but had not occurred to them when the 400 cal serving of rice was offered as the implicit default . However, defaults are less effective when preferences are strong. When preschool children were provided apple slices as the default side but allowed to switch to French fries, their strong preference for fries led the vast majority to reject the default apples .
In addition to improving the possibilities and the choice process, there are many opportunities for nudging people toward healthy choices through persuasive communication. We next turn to interventions in this domain—Persuasion.
Interventions through Persuasion change behavior by providing information and persuasive messages, as well as relying on social norms. Persuasive messaging covers what information is presented, how it is framed and communicated, at what moment it is presented, and who delivers the message. Persuasion interventions include visuals, descriptors, and “moments of truth.”
Persuasion through visual images targets System 1, and can make healthy options more tempting, or unhealthy items aversive. For example, viewing a vial of fat from a gallon of whole milk stimulated a disgust response, motivating a switch to skim . Simple visual classification systems provide a heuristic System 1 can easily apply. Thorndike et al.  found that a simple green/yellow/red (traffic light) color-coding scheme increased the sales of healthy items (green) and reduced sales of unhealthy items (red) in a large hospital cafeteria.
Names can speak to the intuitive system as well. Researchers have found that using vivid adjectives such as “succulent” or “homemade” makes foods more appealing, tastier, and even more filling . In a national Healthy Lunchrooms initiative, vivid names such as “Florida Fresh Oranges” increased fruit consumption in school cafeterias by 26 % . Naming also impacts a meal’s perceived healthfulness, and hence the amount that people eat. People tend to eat more pasta salad when it is called the “salad special” than the “pasta special” . Similarly, people eat more when portions are called “small” or “medium”—although they believe they have eaten less .
Successful persuasive communication requires sending the right message at the time when the individual will be most receptive to it. Although an individual pursues many goals, only a small number are active in any particular moment . Planners can time persuasive messages to coincide with “moments of truth” in which the relevant goals are salient, or they can try to cue the relevant goals. A planner wishing to remind people to take the stairs might place signs next to or on the elevators, when people are thinking about their goal of getting upstairs. Stair prompts with messages such as “Burn calories, not electricity” have been found to be highly effective, increasing stair use by as much as 40 %, even 9 months later . A planner intending to cue a goal such as dieting must be careful what stimuli they use, since some will cue differing, even opposite responses across people with differing goals. One study found that exposing dieters to images of diet foods instead of non-food images successfully reduced subsequent snack consumption, presumably because these images made their diet goal salient. However, the same images increased snack consumption among non-dieters, presumably because seeing pictures of food cued the desire and goal to eat .
Interventions in the Person category shift the focus from the individual decision in a particular context to helping decision makers make better choices across contexts. Most attempts to change people’s general behavior are purely informative, offering advice . However, we have already discussed why in the case of food decisions, intentions and actions are not always consistent—primarily because resisting temptation requires resources such as attention and willpower, which are often in short supply. Fortunately, there are a few simple ways to support healthy intentions, relying less on System 2 processing and willpower. The specific routes we suggest for influencing a person to help them make healthy choices are goals, habits, and precommitment.
Setting explicit goals can increase healthy choices by reducing the thinking required for engaging in a healthy behavior. Effective goals are motivational and measurable—challenging, specific, and concrete . For example, a concrete goal to lose 10 lb in 5 months or to run 3 mi three times a week for the next 5 months would be more effective than a general goal to “lose weight,” where progress is not measurable and there is a lack of feedback. In addition, goals are more manageable and effective when they are broken into smaller steps. Tracking small wins along the way builds momentum: feeling progress towards a goal is motivating .
While setting goals and tracking progress encourages healthier behavior by appealing to intrinsic motivation, planners can also encourage healthy behavior through extrinsic motivation, or incentives. Incentives shift the relative balance of costs and benefits toward a desired option, and in some cases, the behavior continues habitually even after the incentive period has ended. Paying participants to regularly go to the gym boosted gym attendance even after the monetary incentive was removed , and paying people to quit smoking has been shown to be effective as well . Promotions such as loyalty cards can be particularly effective because they link the financial incentive with a sense of progress towards a goal, combining extrinsic and intrinsic motivation .
Unlike goals, which require conscious focus and effort to stick to them, a habit is a behavior that is initiated effortlessly and automatically, triggered by a relevant cue in the environment . Habits have become automatic over time through repetition, and they can be modified by changing environments or cues . Research shows that environmental cues are extremely powerful in shaping habits, and in many cases, environmental cues trigger unhealthy food habits. For example, entering a movie theater can cue a mindless popcorn consumption habit. In one study , habitual popcorn eaters consumed just as much popcorn while watching a movie if the popcorn was stale as if it was fresh (despite complaining about it), while non-habitual eaters ate less when the popcorn was stale.
Given that habits are cued by the environment with minimal decision making, successful interventions involve disrupting those environmental factors. Behavior can be modified by changing environments or cues , although overcoming habits is hard. Eradicating poor habits is most effective when people change their environment: while traveling, after a move, or in periods of change or restructuring .
A final way to encourage people to make healthy choices is through precommitment—committing to a future course of action. Precommitment works by reducing reliance on willpower, allowing people to choose for the future when they are in a “cold state” rather than choosing for the present, in a “hot state” . A commitment device commits a person to a future course of action, preventing or penalizing divergence from it. In an elementary school field study, children who pre-ordered their lunch entrée were nearly twice as likely (29 vs. 15 %) to choose the healthier option .
Another form of precommitment, “temptation bundling,” allows people to restrict their use of a tempting option (e.g., listening to enjoyable audiobooks) to coincide only with their engaging in a virtuous behavior (e.g., exercise) . In one large field study using a penalizing precommitment, more than a third of grocery store customers chose to risk losing money when they precommitted to increasing their purchase share of healthy items —and they subsequently purchased a greater share of healthy foods than did a control group who had made the same choice hypothetically. People are even willing to pay money for commitment devices: smokers pay a premium to buy smaller packs of cigarettes to ration their smoking .
We have considered different angles through which planners can impact the individual decision maker: both internal and external motivation to set goals, ways to gradually change habits, as well as commitment devices that decision makers can use to better adhere to their goals. These three approaches have potentially high payoffs because, by influencing people’s patterns of behavior, they produce a long-term impact. Interventions focusing on the person can build healthy patterns of behavior over time, which can sometimes lead to these positive behaviors becoming habitual.
In this section we have introduced a novel unifying framework—the 4Ps Framework for Behavior Change—that serves as a useful way to organize research findings in psychology, behavioral economics, and marketing in order to stimulate new ideas among researchers and to help planners make healthy choices easier. In the next section, we discuss some challenges for future research on encouraging healthy behavior as well as some fruitful areas for future research.