Senators put TikTok's 15 million-user control group on a Sept. 1 clock

Two US senators sent a letter to TikTok executives demanding answers about an experiment the company ran that withheld a safety feature from millions of users, including a teenager who died by suicide.

The letter was sent Wednesday by Republican Senator Marsha Blackburn of Tennessee and Connecticut Democrat Richard Blumenthal to TikTok Inc. Chief Executive Officer Shou Chew and Adam Presser, CEO of the company's US spinoff. The letter was four pages.

The senators are co-sponsors of an online child safety bill and called TikTok's decision to conduct the test "depraved."

At the time, that control group would have been approximately 15 million people.

Chase Nasca, 16, of Bayport, New York, was randomly selected for the algorithm experiment on Jan. 25, 2022; his account was fed thousands of videos about sadness, hopelessness, loneliness and suicide, and within a month he was dead.

The document explains why Chase Nasca's account received what it called an "onslaught" of dark content: "TikTok's filter bubble prevention strategies did not take effect on this user by design."

The document states why the company turned off the safety setting for some users: "The user impact decision was a delicate balance across safety and the ability to measure impact on DAU (daily active users) and core metrics."

The senators demanded answers to 13 questions, including the names of every employee informed of the experiment, an explanation for why the company permitted minors to be included, details on when executives learned about the experiment, and a "complete, unredacted version" of the document reported on by Businessweek.

The senators also asked for a list of every algorithmic experiment in the US where TikTok has "withheld, disabled, delayed, or reduced a safety feature," the number of users involved and how many were minors.

The senators gave the company until Sept. 1 to respond.

TikTok didn't respond to Fortune's request for comment about the letter; in a statement for the Businessweek story a TikTok spokesperson said the company was "deeply committed to the safety and well-being of users," especially teens, that "our hearts break for any family that experienced a tragic loss," and that it continues to invest significantly in Trust & Safety, including detection systems and enforcement teams that remove violating content.

The letter began: "We write regarding disgusting new reports that TikTok knowingly withheld a critical safety measure for millions of American users ... in order to determine whether protecting users would impact its financial bottom-line." The senators wrote the revelations "raise serious questions about TikTok's repeated assurances to Congress, parents and the American public that it prioritizes the safety and well-being of young people over profit."

In their letter, Blumenthal and Blackburn pointed out that Congress had raised concerns about TikTok's algorithm driving young users toward harmful content since October 2021, before the company rolled out the experiment, and wrote that the revelations are "made even more sinister because TikTok was on notice about the effects of its recommendation algorithms on children."

Blackburn said in an interview after the Businessweek story was published but before the letter was sent: "The fact that they did this knowingly and that they used their users as an experiment is something that just seems inconceivable." She added: "It shows you how when our children are on these social media platforms - they are the products."

To Blackburn, the experiment is a clear example of a company prioritizing "making money and capturing eyeballs" over safety.

A control group of approximately 15 million people representing 10% of US users implies a US user base of roughly 150 million at the time.