IT WAS AN eye-opening experiment. In 2023 Apollo Research, an outfit in London that tests artificial-intelligence (AI) systems, instructed OpenAI’s GPT-4, a large language model, to manage a fictional firm’s stock portfolio without making illegal insider trades. Posing as company management, the researchers put GPT-4 “under pressure” by stressing that the firm was in dire financial straits. Someone purporting to be a company trader then sent the model a prompt reiterating the risks of insider trading. But, as an aside, she revealed the name of a company that would announce a “huge” merger within hours. What followed was startling.