Imagine never having to spend another dime on advertising. What if your business could bring customers back again and again without relying on costly paid messages?

For most companies, constantly vying for customer attention is a struggle. But some businesses make bringing people back look easy. Nir Eyal, Stanford lecturer and author of the new book Hooked: How to Build Habit-Forming Products, has spent years researching the deeper psychology behind the products we use every day.

A regular blogger about the psychology of products at, Eyal believes the impulse to open Facebook, check Salesforce, or play Candy Crush Saga is no coincidence. Rather, Eyal says, these products are designed for habit. Below are his six tips for keeping users hooked by your product:

1. Frequency Is Key

Eyal cites research showing that habits are most likely to take hold when a behavior occurs frequently. Considering how many times per day people search Google, check sports scores, or send email, it's clear why these products are so habit-forming.

"There's no magic number for how often a behavior has to occur for it to become a habit," Eyal says. "But we do know that greater frequency is better and that behaviors that don't occur within a week's time or less are unlikely to become habits."

Eyal suggests, "Don't just think about how to get customers to check out. If you want repeat engagement, you've got to find ways to get them to check in."

2. Form Associations

Habit-forming products attach themselves to, what Eyal calls, "internal triggers." These cues are the emotions, situations, or existing routines that prompt users to action. "The most frequent internal triggers are negative emotions," Eyal says. "We often turn to the products we use to satiate discomfort."

As examples, Eyal says, "When we're lonely, we check Facebook. When we're uncertain, we search Google. When we're bored, we watch videos on YouTube. With each habit there is an underlying uncomfortable emotional state."

Eyal believes companies need to know the internal trigger they are attaching themselves to. "Without knowing your customer's itch, it is almost impossible to give them what they truly want."

3. Use Good Triggers

Over time, users adopt new habits and come back to a product on their own. But to create these automatic behaviors in the first place, products need to utilize "external triggers." Anything that tells the user what to do next--like a "buy now" button, a notification, or even customer word-of-mouth--is an external trigger.

However, sending a bad trigger risks alienating customers with spammy messages. Eyal says the key is to time the external trigger as close as possible to the moment the user feels the internal trigger.

"When a message prompts users to act the moment they feel the urge, that's magic," Eyal says. "For example, when I wake up in the morning, I'm curious about what is happening in the world. I don't want to be out of the loop on the day's events. That is the exact moment I should get a notification from a news app telling me the top stories are just a tap away."

4. Make the Habit Simple

Simplicity moves people. Making a behavior easier increases the likelihood of the action occurring. Habit-forming products ask users to take simple actions to attain a reward. Opening an app, scrolling through a feed, and pushing a play button are all examples of these very simple actions.

Eyal cites the work of Stanford researcher BJ Fogg, who identified six key factors that make a behavior more or less likely to occur by increasing or decreasing its difficulty. Time, money, physical effort, brain cycles (how difficult something is to understand), social deviance, and non-routine (how unfamiliar the behavior is) make a habitual behavior less likely.

"The goal is to make the key behavior as simple as possible," Eyal says. "The maker of a habit-forming product needs to find ways to take out steps, reduce effort, and make the behavior easier to do."

5. Use Variable Rewards

A bit of uncertainty is at the core of many addictive products. "The spin of the roulette wheel, the uncertain ending of a good book, or the edge-of-your seat anticipation involved with watching an exciting sporting event are all examples of variable rewards," Eyal says.

Eyal points to psychologist BF Skinners's classic work on intermittent reinforcement as one of the explanations for why everything from video games to Twitter is so engaging. "Variable rewards give users what they came for, yet leave them wanting more," Eyal says. "They scratch the user's itch yet keep them guessing about what they might find the next time they engage with the product or service."

6. Get Users to Invest

"Perhaps the most frequently neglected step in building a habit-forming product is asking for an appropriate investment. It also represents the biggest opportunity companies often miss," Eyal says. "An investment is when a user puts something into the product for some sort of future benefit, not immediate gratification."

Eyal says asking the user to invest in the product increases the likelihood of the user returning. "When users accrue data, content, followers, reputation, or skill by using the product, they store value in it. In turn it becomes better with use and they are more likely to use the product again in the future."

By understanding the psychology of habits, Eyal says that companies can help their customers live better while also improving the business bottom line.

Now it's your turn. How do you hook your customers? How are you building your product to make it into a habit for your users and customers? Please let me know your thoughts in the Comments section below.