USC researchers may have found the biggest influencer in the spread of fake news: social platforms' structure of rewarding users for habitually sharing information. The team's findings, published Tuesday by Proceedings of the National Academy of Sciences, upend popular misconceptions that misinformation spreads because users lack the critical thinking skills necessary for discerning truth from falsehood or because their strong political beliefs skew their judgment. Just 15 per cent of the most habitual news sharers in the research were responsible for spreading about 30 per cent to 40 per cent of the fake news.