While AI can perform incredibly well with tasks that have clear parameters, such as a game of chess, humans are still better at making the tough calls and dealing with unpredictable situations. Gray shares the example of Uber wanting to verify its drivers' identities with a current selfie matched against a photo on file. A machine trained in facial recognition can match faces fairly reliably, but it can't compare to a human eye when it comes to added variables -- a mask or a new beard, for instance. Humans, therefore, remain at the core of things like removing objectionable content from Facebook or interpreting special instructions in your GrubHub order. Gray suggests there are millions of people doing this "ghost work," but we don't actually have firm numbers.