We’ve all heard it before — maybe even said it ourselves, or even wrote it in a book, such as I did: “Students learn better when they already know a lot about the topic.” It’s the classic knowledge-is-power hypothesis that a solid knowledge base gives you a leg up when learning something new. It’s backed by theories of expertise, endorsed in teacher training, and often repeated in staff meetings when test scores come in.

But what if that’s not entirely right?

A new experimental study challenges this long-standing belief. Researchers Zachary Buchin and Neil Mulligan set up a clever design: first, they trained students in three of four topics in a domain like psychology or geology. Later, they gave them new material, including one untrained topic in the same domain and four topics from a completely different one. If prior domain knowledge really boosts learning, students should do better on the new topic within the domain they were trained in.

They didn’t.

The result was the same across different measures—final test scores, absolute learning gains, and normalised gains—having more domain-specific knowledge didn’t help students learn the new topic better, not even a little. Bayes factors even gave moderate support for no effect at all.

This matters.

Most earlier studies showing benefits of prior knowledge were correlational, which means we couldn’t tell cause from coincidence. Maybe students who start with more knowledge also have more motivation or better memory. Buchin and Mulligan solved that by randomly assigning students to domains and topics, and keeping everything else constant.

And still, no benefit for new learning.

Yes, students who were trained in a topic remembered more facts about it later — but that’s not surprising. What’s new is that their background knowledge didn’t transfer to help them understand other material in the same domain. Even when they reported the learning felt easier, it wasn’t actually more effective.

So, where does this leave us?

It doesn’t mean prior knowledge is useless — far from it. It still plays a role in comprehension, memory, and reasoning. But maybe its role in new learning is more limited than we assumed. Or more context-dependent. Perhaps it matters more when building deep conceptual schemas than learning isolated facts. Maybe it matters when there’s more time, when learning is self-directed, or when prior knowledge is activated explicitly.

But those are still maybes.

For now, this study reminds us to be careful with educational clichés. Just because something feels intuitively true doesn’t mean it holds up in all situations. Even in education, power comes not from knowledge alone, but from being willing to rethink what we thought we knew.

Abstract of the study:

It is commonly claimed that higher domain knowledge enhances new learning—the knowledge-is-power hypothesis. However, a recent meta-analysis (Simonsmeier et al., 2022) has challenged this idea, finding no overall relationship between prior knowledge and new learning across hundreds of highly variable effect sizes. The authors note that this variability and lack of randomized controlled experiments preclude broad claims regarding the influence of prior knowledge on learning. The present study (conducted in 2020) provides an experimental assessment of the causal effect of prior domain knowledge on new learning. Participants were randomly assigned to receive training in one of two academic domains over 3 days before learning new information about topics in both domains for a later test. Training was specific to three of four topics within that domain, allowing the untrained topic in the trained domain to act as a measure of new learning in that domain. New learning, measured as final test performance or knowledge gains, did not differ between the high and low domain knowledge conditions. Experimentally induced prior domain knowledge did not affect new learning.