Although understanding how causal attributions for performance develop is important to attribution theory, little research has been done on this topic. To explore changes in attributions during task performance for both actors and observers, 90 female undergraduates participated in a procedure in which they received either 80 percent or 20 percent success feedback. After either 5, 20, or 40 trials they computed attribution measures. Subjects were randomly assigned to the role of actor or observer. The task involved raising a ball bearing balanced on a carriage to the top of a platform using a cord and pulley. Unknown to subjects, an electromagnet was used to affect outcome. Results showed that regardless of reinforcement level, at 20 trials observers were more internal than actors; but at 40 trials, actors were more internal than observers, indicating that attributional differences developed over time and developed differently for actors and observers. Actors' focus may shift from the situation toward themselves, and observers' focus may shift from the actor toward the situation. (JAC)