"Younger children are simply not ready to have social media accounts", the letter reads. "They are not old enough to navigate the complexities of online relationships, which often lead to misunderstandings and conflicts even among more mature users".
Facebook's global head of safety Antigone Davis has responded to the letter by saying that the company has made Messenger Kids as safe as possible for kids by collaborating with child health experts.
"Younger children are simply not ready to have social media accounts", the Campaign for a Commercial-Free Childhood, ACLU of Massachusetts, Common Sense Media and others write.
Facebook stressed Messenger Kids contains no advertising and said that parents who use the app say it helps them stay in touch with their children during work hours or when they are away.
However, the group of experts who co-signed the letter believe that encouraging kids to take their friendships online will displace face-to-face interactions, which they say are essential for building healthy developmental and reading skills, as well as an ability to connect with human emotion and engage with the physical world. "Almost half of parents say that regulating their child's screen time is a constant battle", the letter says.
The groups add that the service will spur children to spend even more time online. He pointed to the abuse and hate on the platform, along with foreign attempts to spread misinformation, and social networking's effect on a person's well being. "They can also just pick up a phone".
Today, in the USA, we're rolling out a preview of Messenger Kids, a new app that makes it easier for kids to safely video chat and message with family and friends when they can't be together in person.
Messenger Kids also includes what Facebook has described as a "library of kid-appropriate and specially chosen GIFs, frames, stickers, masks and drawing tools lets them decorate content and express their personalities". Last year, it joined a coalition of advocacy groups protesting an artificial-intelligence-powered home hub aimed at kids by Mattel. Although access to apps can be restricted, in practice there's little to prevent children with mobile devices from creating social media profiles.
And for the past several months, many families at Messenger and Facebook have used the app and helped come up with some of the key features like the easy-to-use parental controls. "Using filters and AR in order to extend the chat will only make it harder for kids to have real conversations without gimmicks in both the short and long run", he says.
Jean M. Twenge is the author of iGen: Why Today's Super-Connected Kids Are Growing Up Less Rebellious, More Tolerant, Less Happy-and Completely Unprepared for Adulthood and a professor of psychology at San Diego State University. We continue to be focused on making Messenger Kids the best experience it can be for families.