Our well-being can improve when people heed evidence rather than simply follow familiar or charismatic advisors who neglect evidence. We developed the Reasoning through Evidence versus Advice (EvA) scale to measure individual differences in reasoning through evidence like science and statistics versus following advisors such as politicians and celebrities. No existing scales directly measure these tendencies; moreover, it was theoretically unknown whether they reflect a single dimension (from evidence- to advice-based) or distinct tendencies to value or distrust each. Our scale validation process included qualitative interviews and four studies that involved 1583 respondents (753 college graduates, 830 non-college graduates) in which we conducted exploratory and confirmatory factor analyses and tests of convergent validity, discriminant validity, and measurement invariance by gender and education. This process yielded a 16-item EvA scale with four dimensions: Pro-evidence, Anti-evidence, Pro-advice, and Anti-advice. In assessing criterion validity, these tendencies identified individual differences in important, real-world attitudes and behaviors, including susceptibility to health misinformation, adherence to CDC guidelines on social distancing, confidence in the COVID vaccine, science curiosity, and religiosity. The EvA scale extends our understanding of individual differences in reasoning tendencies that shape critical attitudes, decisions, and behaviors and can help promote informed decisions.