Tech companies use “persuasive design” to get us hooked. Psychologists say it’s unethical.

Behind the screens of the games we play and digital communities we interact with are psychologists and other behavioral science experts, who are hired to create products that we want to use more and more. Big tech now employs mental health experts to use persuasive technology, a new field of research that looks at how computers can change the way humans think and act. This technique, also known as persuasive design, is built into thousands of games and apps, and companies like Twitter, Facebook, Snapchat, Amazon, Apple, and Microsoft rely on it to encourage specific human behavior starting from a very young age.

While defenders of persuasive tech will say it can have positive effects, like training people to take medicine on time or develop weight loss habits, Chavie Lieber reports in Vox that some health professionals believe children’s behaviors are being exploited in the name of the tech world’s profit. On Wednesday, a letter signed by 50 psychologists was sent to the American Psychological Association accusing psychologists working at tech companies of using “hidden manipulation techniques” and asks the APA to take an ethical stand on behalf of kids.

Lieber interviewed Richard Freed, a child and adolescent psychologist, author of Wired Child: Reclaiming Childhood in a Digital Age, and one of the authors of the letter, which was sent on behalf of the nonprofit Campaign for a Commercial-Free Childhood.