Previous research has demonstrated that implicit evaluations can be reversed with exposure to a single impression-inconsistent behavior. But what exactly is changing when perceivers encounter diagnostic revelations about someone? One possibility is that rapid changes are occurring in the extent to which perceivers view the person positively or negatively. Another possibility is that they override the expression of initial evaluations through control-oriented processes. We conducted three studies (one preregistered) that used multinomial process trees to distinguish between these possibilities. We find consistent support across two different implicit measures that diagnostic behaviors result in rapid changes in evaluative processes. We obtained only inconsistent evidence for effects on more control-oriented processes. These findings thus help to reveal the cognitive processes underlying rapid implicit revision. Implications for theoretical perspectives on implicit attitudes are discussed.