CAR Model

Your sleep habits aren’t the best, especially as the weekend comes to a close and the Sunday scaries set in. It seems so simple: go to bed at an earlier time to build better sleep habits. Yet there are some aspects of your environment—like your roommate washing dishes late at night, inconsistencies in your routine, and a lack of reward when you do get to sleep on time—that seem to get in the way. To change this, you might consider applying the cue-action-reward (CAR) model. 

The CAR model, also known as the habit loop, breaks down habits into three distinct parts: cue, action (routine), and reward. According to its creator, Charles Duhigg, the habit loop shows us how and why habits form.¹ Drawing from behavioral theories from psychology and neuroscience, Duhigg was the first to introduce the habit loop in his 2012 book, The Power of Habit.² Whether you’re looking to break a bad habit or hoping to form a good one, the CAR model might be the tool for you. The more that someone engages in the habit loop, the more ingrained a habit becomes.³ Let’s take a closer look at the three parts of the CAR model and consider a fourth component that serves as a natural expansion of the original framework.

The Cue 

Sometimes labeled as a reminder, the cue acts as a trigger, initiating the habit loop by signaling when and where a specific behavior should occur. You can probably think of many cues that relate to your poor sleep habits—your own internal thoughts but also external factors like the temperature of your bedroom, the noisiness of your roommates, or the softness of your pillow. A handful of common cue categories may include, but are not limited to:

1. Time
2. Place
3. Emotions
4. Others around you
5. Your most recent action 

For instance, the sound of your alarm clock in the morning: is it a favorite song, birds chirping, a tolerable default alarm noise, or something else? That noise is what you associate with waking up, signaling that it's time to get ready for work, which elicits certain feelings. Perhaps your weekend alarm is a different sound—or no sound at all, so it has a different association from your weekday wake-ups. 

The Action 

Often referred to as routine, the action is the behavior performed in response to the cue. The action forms the core of the habit loop. These actions are often unconscious, like checking your text messages first thing in the morning after turning off the alarm on your phone. Whether a habit is conscious versus unconscious makes a difference, especially when it's time to use the habit loop to make a change. While your reaction to your alarm clock is rather unconscious, where you choose to get your morning coffee may be more deliberate depending on how you’re feeling. 

The Reward 

The reward provides positive feedback, reinforcing the behavior and increasing the likelihood of repetition in the future. Rewards are effective at cementing habits so that they actually stick. For each of us, the types of rewards that are most beneficial may be highly subjective. No matter what reward works best for you, we shouldn’t underestimate our brain’s ability to form associations between cues, actions, and rewards—which combine to form the habit loop. It is key to be aware that some “rewards” can be detrimental. When it comes to bad sleep, there may likely be a trend of “bad” rewards keeping you up at night, such as scrolling for hours, promising yourself you’ll watch just one more TikTok. 

Adding Another C onto CAR: the Craving

In addition to the original three components of the CAR model, a fourth step may be considered: the craving.⁴ This would be the second step in the loop, representing the motives behind all of your habits. In the absence of motivation, it is unlikely that the proceeding step of an action will occur. Cravings may be understood as a wish to change internal feelings that arise due to a cue. For example, you crave the sugar rush you get from eating a Kit Kat. Of course, we don’t all have the same cravings—nor are we all tempted by the same cues. Not everyone has a sweet tooth like you, but someone else may have just as strong of a desire for a nice crunchy pickle. 

The Habit Loop and its Phases

A habit forms when an action feels sufficient at all four stages. Without a cue, there is no habit, or if a craving is weak, there won’t be enough motivation. With the addition of the latest element of the habit loop, cravings, let’s take a closer look at the loop in action.

The depiction of the cue-action-reward model as circular makes it easy to understand each stage of the loop. It goes as follows: a cue causes a craving, which motivates an action or behavior, which grants a reward that fulfills a craving, eventually forming an association with the cue.4 The habit loop can be seen as a neurological feedback loop that results in habitual behaviors when these steps are combined and repeated. 

We can divide the four steps into two larger categories known as the problem phase and the solution phase. The former captures the cue and craving, which create a desire to act, whereas the latter explains how the response and reward reinforce or modify the habit. Let’s dive into our Kit Kat example to sort out how the problem and solution phases appear in real situations:

Forming Good Habits and Breaking Bad Ones 

Whether it's about making new constructive habits or trying to eliminate old harmful ones, there is a framework we can apply to our behavior. The Four Laws of Behavior Change provide rules for addressing both good and bad habits, each influencing the actions you decide to take.⁴ When these laws are set up in a way that works for an individual, making good habits becomes easy—but if they aren’t in alignment with your goals, good habits feel unreachable. 

Let’s look at these laws for creating good habits first:⁴

In contrast, the laws can be inverted for breaking bad habits:⁴