When the markets are extremely volatile, it is common to want to find a scapegoat. And you might be thinking: It’s got to be the algorithms, right? Two kinds are used in Wall Street trading: those that optimize trades that humans make and those that take risks on their own. Marketplace Tech host Molly Wood talks with Michael Kearns, a professor of computer science at the University of Pennsylvania, who creates algorithms that are used on Wall Street. He said that generally, the algorithms are not to blame for drops in the market.