Residual expertise - or why scientists are amateurs at most of science

Jeff Leek

Editor’s note: I have been unsuccessfully attempting to finish a book I started 3 years ago about how and why everyone should get pumped about reading and understanding scientific papers. I’ve adapted part of one of the chapters into this blogpost. It is pretty raw but hopefully gets the idea across. 

An episode of_ The Daily Show with Jon Stewart_ featured physicist Lisa Randall, an incredible physicist and noted scientific communicator, as the invited guest.


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Near the end of the interview, Stewart asked Randall why, with all the scientific progress we have made, that we have been unable to move away from fossil fuel-based engines. The question led to the exchange:

Randall: “So this is part of the problem, because I’m a scientist doesn’t mean I know the answer to that question.”


** Stewart: ”Oh is that true? Here’s the thing, here’s what’s part of the answer. You could say anything and I would have no idea what you are talking about.”

Professor Randall is a world leading physicist, the first woman to achieve tenure in physics at Princeton, Harvard, and MIT, and a member of the National Academy of Sciences.2 But when it comes to the science of fossil fuels, she is just an amateur. Her response to this question is just perfect - it shows that even brilliant scientists can just be interested amateurs on topics outside of their expertise. Despite Professor Randall’s over-the-top qualifications, she is an amateur on a whole range of scientific topics from medicine, to computer science, to nuclear engineering. Being an amateur isn’t a bad thing, and recognizing where you are an amateur may be the truest indicator of genius. That doesn’t mean Professor Randall can’t know a little bit about fossil fuels or be curious about why we don’t all have nuclear-powered hovercrafts yet. It just means she isn’t the authority.

Stewart’s response is particularly telling and indicative of what a lot of people think about scientists. It takes years of experience to become an expert in a scientific field - some have suggested as many as 10,000 hours of dedicated time. Professor Randall is a scientist - so she must have more information about any scientific problem than an informed amateur like Jon Stewart. But of course this isn’t true, Jon Stewart (and you) could quickly learn as much about fossil fuels as a scientist if the scientist wasn’t already an expert in the area. Sure a background in physics would help, but there are a lot of moving parts in our dependence on fossil fuels, including social, political, economic problems in addition to the physics involved.

This is an example of “residual expertise” - when people without deep scientific training are willing to attribute expertise to scientists even if it is outside their primary area of focus. It is closely related to the logical fallacy behind the argument from authority:

A is an authority on a particular topic

A says something about that topic

A is probably correct

the difference is that with residual expertise you assume that since A is an authority on a particular topic, if they say something about another, potentially related topic, they will probably be correct. This idea is critically important, it is how quacks make their living. The logical leap of faith from “that person is a doctor” to “that person is a doctor so of course they understand epidemiology, or vaccination, or risk communication” is exactly the leap empowered by the idea of residual expertise. It is also how you can line up scientific experts against any well established doctrine like evolution or climate change. Experts in the field will know all of the relevant information that supports key ideas in the field and what it would take to overturn those ideas. But experts outside of the field can be lined up and their residual expertise used to call into question even the most supported ideas.

What does this have to do with you?

Most people aren’t necessarily experts in scientific disciplines they care about. But becoming a successful amateur requires a much smaller time commitment than becoming an expert, but can still be incredibly satisfying, fun, and useful. This book is designed to help you become a fired-up amateur in the science of your choice. Think of it like a hobby, but one where you get to learn about some of the coolest new technologies and ideas coming out in the scientific literature. If you can ignore the way residual expertise makes you feel silly for reading scientific papers you don’t fully understand - you can still learn a ton and have a pretty fun time doing it.