Two leading hypotheses for why individuals unintentionally share misinformation are that 1) they are unable to recognize that a post contains misinformation, and 2) they make impulsive, emotional sharing decisions without thinking about whether a post contains misinformation. Much of the literature on interventions to counter misinformation focuses on the first hypothesis and tests interventions that educate social media users about reasoning-based techniques employed in social media posts to mislead them; however, other work shows that emotions are important for the spread of and belief in misinformation, supporting a focus on the second hypothesis and emotion-based techniques. To learn whether interventions to counter reasoning- or emotion-based techniques are more effective, or whether the approaches are complementary, we evaluate three distinct versions of a five-day, low-cost, and scalable text message educational course in a field experiment with approximately 9,000 participants in Kenya. We assess the impact of the courses through a pre-post survey design eliciting intentions to share, finding that all treatment courses work, decreasing misinformation sharing 28% on average relative to no text message course. Treating the emotional drivers of misinformation sharing in the “Emotions” course is more effective than teaching about reasoning-based techniques either alone in the “Reasoning” course or in combination with emotion-based techniques in the “Combo” course. Moreover, the Emotions course performs best on misinformation posts that use emotion-based techniques, and does no worse than the Reasoning or Combo courses on misinformation posts that use reasoning-based techniques. In a follow-up experiment approximately two months later, 88% of the treatment effect of the three courses on misinformation sharing persists.