If you ask 10 Americans if they’ve gambled in the past year, 6 of them will say yes.

Gambling is a vice of choice for many, and for good reason. It’s designed to be addictive.

This is in part due to a concept discovered by B.F. Skinner known as a variable schedule of rewards or “variable ratio scheduling”. Skinner conducted tests in the 1950s that concluded: If you build a system which produces a positive result after a random number of responses, you condition the user to respond at a rapid and steady rate.

Skinner learned this by running tests on rats. They were kept in a cage with a lever which delivered food when pressed. When the food was provided at random intervals, the rats would press the lever madly until a reward was received.

Slot machines in casinos replicate this experiment. Gamblers sit in front of the machines for hours, feeding in coins and repeatedly pulling the lever. Slots came way before Skinner’s breakthrough. He made his discovery in 1950s, while the first slot machines had already been invented in 1891.

In gambling, you give up money in exchange for a chance at winning more money. The gamblers behavior follows this equation:

• Money * Random Chance = Random Amount of Money

For the rats, they gave up their time to pull the lever in exchange for a chance at receiving food. The rats behavior follows this equation:

• Lever Pull * Random Chance = Food (Sometimes)

The two above behavior systems mirror a similar behavior most of us engage in daily: Looking at our phones.

We give up our time, attention, and focus in exchange for a chance to get a small hit of dopamine. The dopamine may come from checking email, scrolling social media, or playing a game. Most of our daily behavior follows the below equation:

• Check Phone App * Random Chance = Dopamine (sometimes)

In all of the variable reward systems above, you can increase the response rate in two ways:

1. Lowering the amount of friction required to respond
2. Reducing the # of responses required before getting a positive result

This makes our phone the strongest variable reward systems in existence. We always have it with us. Checking our notifications is as simple as looking at the screen, and the developers of the apps control how often we get positive results. (Which they optimize to make us spend more time on their apps).

For me, I’ve fallen into this trap more times than I would like to admit.

I’ve done it in the past with social media and I do it daily by checking my work email.

If an outcome of any daily habit is random, be wary of it. It can be just as addicting as playing slots.