In bistable perception, several interpretations of the same physical stimulus are perceived in alternation. If one interpretation appears to help the observer to be successful in an auxiliary task, will that interpretation be seen more often than the other? We addressed this question using rivalrous stimuli. One of the elicited percepts presented an advantage for a separate visual search task that was run in close temporal proximity to the rivalry task. We found that the percept that was useful for the search task became dominant over the alternate percept. Observers were not aware of the manipulation that made one percept more useful, which suggests that usefulness was learned implicitly. The learning influenced only the first percept of each rivalrous presentation, but the bias persisted even when the useful percept was no longer useful. The long-lasting aspect of the effect distinguishes it from other documented attentional effects on bistable perception. Therefore, using implicit learning, we demonstrated that task usefulness can durably change the appearance of a stimulus.