Some researchers have theorized that emotions while reading science texts influence learning in a wholistic way, such that overall positive or negative affect leads to different learning outcomes. Other researchers have envisioned that emotions fluctuate during reading such that the degree of cycling impacts the learning outcomes. In this study, participants read both expository and refutational science texts sentence-by-sentence. They described how each sentence made them feel and why. They completed the Force Concept Inventory before and after reading. The amount of positive emotions predicted conceptual growth for both types of texts. Students who tended to switch their emotions more often and had a variety of emotions also tended to learn more than other students. These results suggest that both types of theories could be true. An overall positive affect might be best, but the most effective students cycle through short periods of negative emotions as well.