July 9, 2020 Reading Time: 3 minutes

A popular link circulating on the internet shows the results of a demonstration. Dr. Richard Davis sneezed, sang, talked, and coughed into agar cultures wearing a standard surgical mask, and again using no mask. The result is a powerful image: The cultures without the mask clearly show more microorganism growth. 

The strongly worded conclusion from the post’s author? Wear a mask. That way, “Lives will be saved.” 

A picture is worth a thousand words, but a picture is not a good substitute for thoughtful analysis. Does the image actually support the conclusion? Or even worse, is the image misleading, steering you to an incorrect conclusion?

Indeed, Dr. Davis’ own conclusion of his demonstration is considerably less emphatic than the author’s: “A mask preventing your spit & breath from flying out of your mouth, even if doesn’t catch it all, will stop some spread of bacteria (see [in this demonstration]) AND LIKELY VIRUS (not seen [in this demonstration]).” ~ Rich Davis, PhD, D(ABMM), MLS June 27, 2020, emphasis in the original.

That’s far less powerful. First, as Dr. Davis is careful to say, the cultures show bacterial growth, not viral growth. Bacteria are much larger than viruses, so a test showing that a mask blocks bacteria gives us no direct evidence that masks help block COVID-19 and other viral infections, such as the flu. 

This doesn’t mean the demonstration is necessarily irrelevant for viral infections. But to inject a dramatic photo of bacterial cultures into the COVID-19 conversation is at best misleading. Masks may or may not be a good idea for you, but Captain Michael Doyle, the commanding officer of a coronavirus testing site, says, “The only mask that the CDC considers safe from you getting the coronavirus, the only way to actually prevent you from inhaling it, is the N95 mask.”  

So, based on Captain Doyle’s statement, should we not bother to wear a mask? Again, masks may or may not be a good idea for you, but his statement is also potentially misleading: Although Captain Doyle is absolutely correct, he is discussing whether the mask protects the wearer. Perhaps we should consider those around us. 

Do you remember what we were taught even before we attended elementary school? “Cover your face with a tissue or handkerchief when you cough or sneeze!” Returning to the sneeze image, a more informative demonstration of bacterial protection would be for Dr. Davis to compare a surgical mask with a simple handkerchief. 

Yet, even that wouldn’t give direct evidence of whether a mask protects either the wearer or others against a virus. The demonstration, after all, uses bacteria and not viruses.

The point is not whether you should wear a mask, or even whether someone should be allowed to force you to use a mask. By now, enough credentialed sources have weighed in on both sides of the issue. As recently as May 22, 2020, the New England Journal of Medicine wrote: “We know that wearing a mask outside health care facilities offers little, if any, protection from infection.” Still, you can find ostensibly reputable sources to support your opinion. Rather, the point is that you should think about that evidence. What does a story, demonstration, or test really say? Does it support the stated conclusion or advice? Does it even bear on your question, or is it simply irrelevant? 

You can always find someone willing to tell you what to do. With so much evidence on both sides of a question, you’d do better to think for yourself.

Ramon P. DeGennaro

Ramon Paul Degennaro

Ramon P. DeGennaro is the Haslam College of Business Professor in Banking and Finance at the University of Tennessee.

Dr. DeGennaro’s current research involves financial markets and institutions, financial regulation, small-firm finance, and public policy. He has published 50 refereed articles on financial market volatility, small firm finance, the term structure of interest rates, financial institutions, prediction markets, and investments. Dr. DeGennaro earned his Ph.D. in Finance from The Ohio State University.

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