Wall Street professionals tell everyday investors what stocks to buy. But now they have to follow some of these amateurs for signs of where the market is headed next.

Venerable institutions Goldman Sachs and Morgan Stanley are tracking the retail trading frenzy, and hedge funds in New York and London have employees combing through the internet forum of Reddit, Twitter or chat startup Discord in search of trading opportunities. They turned to these sources following a period of market mayhem dominated by amateurs on Reddit’s WallStreetBets and the Robinhood Markets trading app who collectively boosted the shares of GameStop and other companies that had fallen out of Wall Street’s favour.