It’s no secret that Facebook does everything in its power to keep users engaged. The company announced just last week a series of miniscule tweaks to its News Feed to make the content even easier to consume. However, as Quartz points out this week, there is a fine line between usability and addiction.

A 2014 study suggests that about six percent of the world’s population has an Internet addiction—and sites like Facebook do everything possible to make that the case. (Another study in 2016 even compared Facebook addiction to cocaine addiction.) Two professors and experts on the topic told Quartz that the platform’s News Feed acts “like a slot machine for the brain” with colorful notifications that act like rewards.

“When the interaction is smooth and requires no thought or difficult-to-remember steps, the behavior will more likely and easily become automated and rewarding,” the professors told Quartz. “[Facebook’s] ultimate objective with these moves is to retain users’ attention and keep them scrolling, posting and using their sites.”

Of course, all of this begs the question: is that an ethical design practice? There’s no denying that Facebook is subtly manipulating us via its design without our consent. In effect, it’s hacking our brains for its own purposes—and that’s a scary thought.