The habit loop, consisting of a cue, routine, and reward, is the foundation of all habits. The author explains that habits are formed when the brain creates a neurological pathway that connects the cue, routine, and reward. The cue is the trigger that initiates the habit, the routine is the behavior itself, and the reward is the positive consequence that reinforces the habit. The habit loop is so powerful that it can override rational thinking and conscious decision-making.

The author illustrates how the habit loop works through various anecdotes, such as the story of Claude Hopkins, a famous advertising executive who used the habit loop to increase sales of a toothpaste brand. Hopkins discovered that people brushed their teeth for the feeling of cleanliness, so he added a minty flavor to the toothpaste, creating a sensation of freshness that became the reward for brushing. This created a habit loop, which resulted in increased sales of the toothpaste brand.

Understanding the habit loop is essential for changing habits. The author suggests that to change a habit, one must identify the cue, routine, and reward that make up the habit. By doing so, one can change the routine while keeping the same cue and reward. The author gives the example of a woman who wanted to quit smoking. She identified that her cue was a feeling of stress, her routine was smoking a cigarette, and her reward was the feeling of relaxation. She changed her routine to going for a short walk instead of smoking, but kept the same cue and reward. This allowed her to break the habit of smoking.

In summary, the habit loop is the fundamental building block of all habits. By understanding the cue, routine, and reward that make up a habit, one can change the routine while keeping the same cue and reward. The author provides numerous anecdotes and examples that illustrate the power of the habit loop, making it clear that changing habits is possible by understanding and manipulating the habit loop.