The document summarizes research on whether "filter bubbles" and "echo chambers" are real phenomena on social media and search engines. It finds that while some individual communities or pages can be ideological echo chambers, comprehensive studies show that users are generally exposed to a diversity of views. Polarization is driven more by a small number of ideological groups rejecting mainstream views than by technology fragmentation. The problem is political polarization in society, not communicative isolation due to algorithms or design. Further research is needed on understanding and combating polarization.