Back in high school chemistry, I remember waiting with my bench partner for crystals to form on our stick in the cup of blue solution. Other groups around us jumped with joy when their crystals formed, but my group just waited. When the bell rang, everyone left but me. My teacher came over, picked up an unopened bag on the counter and told me, “Crystals can’t grow if the salt is not in the solution.”
To me, this was how science worked: What you expect to happen is clear and concrete. And if it doesn’t happen, you’ve done something wrong.
If only it were that simple.
It took me many years to realize that science is not just some series of activities where you know what will happen at the end. Instead, science is about discovering and generating new knowledge.
Now, I’m a psychologist studying how scientists do science. How do new methods and tools get adopted? How do changes happen in scientific fields, and what hinders changes in the way we do science?
One practice that has fascinated me for many years is replication research, where a research group tries to redo a previous study. Like with the crystals, getting the same result from different teams doesn’t always happen, and when you’re on the team whose crystals don’t grow, you don’t know if the study didn’t work because the theory is wrong, or whether you forgot to put the salt in the solution.
The replication crisis
A May 2025 executive order by President Donald Trump emphasized the “reproducibility crisis” in science. While replicability and reproducibility may sound similar, they’re distinct.
Reproducibility is the ability to use the same data and methods from a study and reproduce the result. In my editorial role at the journal Psychological Science, I conduct computational reproducibility checks where we take the reported data and check that all the results in the paper can be reproduced independently.
But we’re not running the study over again, or collecting new data. While reproducibility is important, research that is incorrect, fallible and sometimes harmful can still be reproducible.
By contrast, replication is when an independent team repeats the same process, including collecting new data, to see if they get the same results. When research replicates, the team can be more confident that the results are not a fluke or an error.
Reproducibility and replicability are both important, but have key differences.
Open Economics Guide, CC BY
The “replication crisis,” a term coined in psychology in the early 2010s, has spread to many fields, including biology, economics, medicine and computer science. Failures to replicate high-profile studies concern many scientists in these fields.
Why replicate?
Replicability is a core scientific value: Researchers want to be able to find the same result again and again. Many important findings are not published until they are independently replicated.
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