Models of reinforcement learning (RL) are prevalent in the decision-making literature, but not all behavior seems to conform to the gradual convergence that is a central feature of RL. In some cases learning seems to happen all at once. Limited prior research on these "epiphanies" has shown evidence of sudden changes in behavior, but it remains unclear how such epiphanies occur. We propose a sequential-sampling model of epiphany learning (EL) and test it using an eye-tracking experiment. In the experiment, subjects repeatedly play a strategic game that has an optimal strategy. Subjects can learn over time from feedback but are also allowed to commit to a strategy at any time, eliminating all other options and opportunities to learn. We find that the EL model is consistent with the choices, eye movements, and pupillary responses of subjects who commit to the optimal strategy (correct epiphany) but not always of those who commit to a suboptimal strategy or who do not commit at all. Our findings suggest that EL is driven by a latent evidence accumulation process that can be revealed with eye-tracking data.epiphany learning | eye tracking | pupil dilation | beauty contest | decision making H ow organisms learn is a central question in the behavioral sciences. Much of the literature has focused on reinforcement learning (RL) (1-3), where organisms gradually adjust their behavior in response to the outcomes of prior actions. However, there are other situations where organisms seem to suddenly and dramatically alter their behavior (4-7), often without any external input (8). This "epiphany" learning (EL) is characterized by an unexpected moment of insight, often portrayed in cartoons by a light bulb appearing over a person's head, and was first introduced to economics in ref. 9.The sudden, unexpected, and irreversible nature of EL makes it inherently difficult to predict or to study. Unlike with standard RL, where the decision maker's choices provide insight into the underlying mechanism, here decisions provide little to no insight into the mechanism underlying the generation of epiphanies, other than to establish that they have occurred ex post (9, 10). An understanding of the EL process thus remains elusive.Here, we sought to tackle this challenging problem with a combination of computational modeling and measures of the choice process. In particular, we use a model from the class of sequential-sampling models (SSMs) (11,12) to capture the unconscious accumulation of evidence toward the epiphany and eye-tracking technology to study this process (13)(14)(15)(16)(17)(18)(19)(20).SSMs have received much attention in the decision sciences for their ability to capture choice outcomes, response times (21-23), and, more recently, eye-tracking and neural activity in perceptual and value-based decision making (24-28). These models assume that at the time of choice the decision maker evaluates the available options and accumulates evidence for each one until there is sufficient relative evidence for one option over the others....