Maybe you’re one of the more than 10 million people who’ve set up an account on Robinhood, the highest-profile example of apps that say they’re increasing access to the stock market by making trades free. Critics say they’re “gamifying” trading, with psychological nudges and push notifications that encourage frequent, and potentially risky, trades. There are few controls or limits for users who may be inexperienced. Jack Stewart speaks with Vicki Bogan, founder of Cornell University’s Institute for Behavioral and Household Finance.