Two leading hypotheses for why individuals unintentionally share misleading information online 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. The strategies to counter each of these drivers of misinformation sharing differ by the techniques that they are designed to address. We categorize techniques according to whether they use misleading reasoning to make recognizing misinformation more difficult (reasoning-based) or manipulate emotions to encourage impulsive sharing decisions (emotions-based). To learn whether interventions designed to counter reasoning- or emotion-based techniques are more effective or whether the approaches are complementary, we evaluate three distinct versions of a low-cost and scalable five-day text message educational course. We assess the impact of the courses in a field experiment with approximately 9,000 participants in Kenya. We measure outcomes using a pre-post survey design that elicits intentions to share and find that all treatment courses work, decreasing misinformation sharing 28% on average relative to no text message course. The treatment designed to counter emotion-based techniques, 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 emotional manipulation, 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.