When an MIT professor called Joseph Weizenbaum created one of the first chatbots in the mid-1960s, he received two shocks in quick succession. The first was how readily people anthropomorphised the rudimentary program, which he called Eliza. “What I had not realised is that extremely short exposures to a relatively simple computer program could induce powerful delusional thinking in quite normal people,” he wrote in his 1976 book Computer Power and Human Reason. But something else troubled him even more: how swiftly people began to envisage what technology like this could do one day, without pausing to ask what it...