When to trust the experts? Follow these guidelines to evaluate science on any topic

Claims about what “studies show” are often delivered with confidence, whether they are based on early-stage research or many years of study across populations and contexts. (Wikimedia Commons/Gwydion M. Williams), CC BY When to trust the experts? Follow these guidelines to evaluate science on any topic Published: August 24, 2026 11.34am EDT Share article Print article When should we trust the evidence and the experts who interpret it for us? A new study makes headlines. It shows a diet works, a supplement sharpens memory, a teaching method transforms reading scores or a management practice improves team productivity. So we adjust how we eat, parent or work. We follow the science. A few months later, another headline overturns the first. Eggs were bad for us, then good again. Red wine protects your heart, or does it? Dark chocolate, low-fat diets, standing desks, masks during a pandemic: Recommendations based on the science keep changing. Eventually, people stop trusting what “studies show.” But that is how science works: Evidence accumulates; early results get tested and some hold up, others don’t. The problem is that we report and act on evolving evidence as if it is final. In a new article, I argue that this tendency to treat preliminary results as if they were conclusive leads to overconfident policy claims and contributes to the declining trust in science. I offer a new framework to help policymakers classify evidence maturity. The insights can guide all of us to interpret scientific evidence in our daily lives. Mature evidence vs preliminary results Claims about what “studies show” are often delivered with confidence, whether they are based on weak early-stage research or confirmed through many years of study across populations and contexts, accumulating into expert guidance and systematic reviews. Is red wine good for your heart? The research is complex. (Unsplash/Alexandra Torro) While mature evidence has survived years of scrutiny, a surprising preliminary result could easily be overturned tomorrow. Yet, reporters, advocates, marketers and even researchers do not always distinguish between them. Politicians, educators and public health leaders build policy on a promising early result, call it “evidence-based,” and then watch the policy fail to deliver as the science evolves. One study is not enough The framework I have developed — PERLS (Policy Evidence Readiness Levels) — offers policymakers a structured way to classify evidence…