Commercial AI chatbots demonstrate racial prejudice toward speakers of African American English – despite expressing superficially positive sentiments toward African Americans. This hidden bias could influence AI decisions about a person's employability and criminality. "We discover a form of covert racism in [large language models] that is triggered by dialect features alone, with massive harms for affected groups," said Valentin Hofmann at the Allen Institute for AI, a non-profit research organisation in Washington state, in a social media post. "For example, GPT-4 is more likely to suggest that defendants be sentenced to death when they speak African American English." Hofmann and his colleagues discovered such covert prejudice in a dozen versions of large language models, including OpenAI's GPT-4 and GPT-3.5, that power commercial chatbots already used by hundreds of millions of people.