Before doctors examine patients, they’re trained to wash their hands, preventing the spread of germs.

History teaches us that a French chemist, Louis Pasteur, made this discovery, but that’s not entirely accurate.

Years before Pasteur, Ignaz Semmelweis, a Hungarian physician and scientist, tried to stop the spread of “childbed fever,” also known as puerperal fever, which was common during the mid-1800s in mothers giving birth, often proving fatal.

Semmelweis concluded from his experience delivering babies that the cause of the childbed fever outbreak might have been due to doctors not washing their hands from birth to birth — ultimately carrying germs and infecting mothers.

At Vienna General Hospital, in the obstetrical ward, Semmelweis then had all doctors wash their hands before and after each delivery. Quickly, the death rate dropped below 2 percent, and childbed fever was no longer a factor.

Despite the success, Semmelweis's hand-washing practices conflicted with the established scientific and medical opinions of the times. Semmelweis was mocked and ridiculed for his conclusions because he could offer no “theoretical proof” to the medical world.

The rejection drove him into a deep state of depression. Eventually, Semmelweis had a nervous breakdown and was admitted into an asylum. Fourteen years later, Semmelweis died from beatings he suffered while in the sanctuary.

Meanwhile, when Pasteur and Joseph Lister confirmed Semmelweis's “germ theory,” they were hailed as geniuses.

So why did the medical community laugh at Semmelweis and applaud Pasteur and Lister? In large part, because of a concept called “Belief Perseverance.”

Belief perseverance is the tendency to maintain one’s beliefs despite evidence contradicting these. There are three different types of belief perseverance:

1. Self-Impressions: A belief about yourself, such as your athletic skills, knowledge, body image or how well you get along with others.

2. Social Impressions: A belief about specific other people, such as beliefs about a best friend, mother or least-favorite teacher.

3. Social Theories. These are beliefs about how the world works, including the causes of war or poverty, stereotypes about teenagers, lawyers or other cultures and other social theories.

Belief perseverance is difficult to overcome, but learning about this bias and thinking of explanations that support an opposing perspective can help reduce it.

Most of us tend to resist change or believe the prevailing opinion. However, being a contrarian all the time doesn’t solve this problem, or as Howard Marks of Oaktree Capital once said about being a contrarian: “Just because most people think it’s a bad idea to stand in front of a bus and you’re a contrarian thinker, it doesn’t mean it’s a good idea to stand in front of a bus.”

Being too rigid in the face of facts won’t work. Being a contrarian won’t either. Therefore, if we recognize our belief perseverance issues, we can work to solve the problems at hand.

Next time you practice “germ hygiene,” think of Ignaz Semmelweis — and the pitfalls of belief perseverance.

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