Confident investors trade more than less confident investors, but why? Prior research tests the ultimate relation between investor confidence and trading, but does not empirically examine the underlying mechanism that explains why confidence leads to trading. We complement the literature by developing a conceptual framework and presenting empirical evidence on a psychologically plausible mechanism through which confidence leads to trading. Using a combination of individual investors' brokerage records and matching monthly survey data, we show that more confident investors rely more on intuitive judgments when forming beliefs about expected returns. In particular, they rely more on naive reinforcement learning and extrapolate individual retu...