  How will superhuman artificial intelligence (AI) affect human decision
making? And what will be the mechanisms behind this effect? We address these
questions in a domain where AI already exceeds human performance, analyzing
more than 5.8 million move decisions made by professional Go players over the
past 71 years (1950-2021). To address the first question, we use a superhuman
AI program to estimate the quality of human decisions across time, generating
58 billion counterfactual game patterns and comparing the win rates of actual
human decisions with those of counterfactual AI decisions. We find that humans
began to make significantly better decisions following the advent of superhuman
AI. We then examine human players' strategies across time and find that novel
decisions (i.e., previously unobserved moves) occurred more frequently and
became associated with higher decision quality after the advent of superhuman
AI. Our findings suggest that the development of superhuman AI programs may
have prompted human players to break away from traditional strategies and
induced them to explore novel moves, which in turn may have improved their
decision-making.
