The head of a U.S. Senate panel examining social media’s negative effects on young people has dismissed as “a public relations tactic” some safety measures announced by Instagram, the popular photo-sharing platform associated with Facebook. 

Adam Mosseri, the head of Instagram, on Wednesday faced off with senators angry over revelations of how the platform can harm some young users and demanding that the company commit to making changes.

Under sharp questioning by senators of both parties, Mosseri defended the company’s conduct and the efficacy of its new safety measures. He challenged the assertion that Instagram has been shown by research to be