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Semmelweis reflex and the innate resistance to data-drivenness

Professor Ignaz Semmelweis is the physician celebrated for his discovery of a relationship of bad hygiene and increased childbirth mortality. His discovery of a need for hand disinfection saved numerous mothers from death with minimal cost and huge returns.

Austrian coin celebrates Ignaz Semmelweis

Nearly two hundred years after his birth he was immortalized in an Austrian 50€ coin and a hungarian university was renamed in his honor in 2000. This guy must have been proud and contempt of his achievements back in 19th century!


Dr. Ignaz Semmelweis died in 1865 after being trapped in and then beaten at Landes-Irren-Anstalt asylum. His remarkable discovery was mostly ignored by the medical community and the original institute of discovery, Vienna’s general hospital, thanked him with an iron hand shake and sacked him.

Most medical lecture halls continue to resound with lectures on epidemic childbed fever and with discourses against my theories. […] In published medical works my teachings are either ignored or attacked. The medical faculty at Würzburg awarded a prize to a monograph written in 1859 in which my teachings were rejected”

Semmelweis reflex

The sad story of Semmelweis has later been shaped into a metaphor. Semmelweis reflex means that people instinctively avoid, reject and belittle any new evidence or knowledge that goes against their established beliefs, practices or values.

This has much to do with organizational change that aims to replace a bit of intuition based (at best) or personal interest based (at worst) decision making with data-driven or data-informed decisions.

It requires tremendous intellectual honesty to avoid Semmelweis reflex. Confirmation bias is another well-recorded psychological phenomenon relevant here. It is complementary to Semmelweis reflex in describing how we are too quick to accept new ideas and facts when they are compatible with our thinking. If they are contradictory, as with Semmelweis, we reject them too easily.

To mention one more shortcoming of human thought against rationality is ownership bias, that is getting so attached to your possessions and ideas that everything else loses value. In my research work, I have demonstrated this preference effect to hold true also for design ideas among professional designers.

From psychological science perspective, we must acknowledge that Semmelweis reflex is founded upon anecdotal evidence. Although it is not theoretically justified, accepting this hypothesis as a useful theory of human psyche, we can derive meaningful guidelines for developing data-driven organizations.

The mental Heimlich manoeuvre against Semmelweis reflex

The very short list of innate biases makes it sound as we’re into bad trouble with trying to promote any data-informed progress anywhere! This is unfortunately true. But there are ways to facilitate the speed of work.

The suggestion comes from Ron Kohavi. He comes from Microsoft and is a long term advocate of data-informed decision making and large scale experimentation. He has also kindly shared many lessons from Microsoft culture of experimentation to the public awareness.

He has presented a view of cultural change that starts from hubris and moves through empirical exploration and acceptance of new findings towards fundamental understanding. Hubris is the stage in which prevailing attitudes and established beliefs keep up and lead to the rejection of new ideas. Semmelweis reflex.

Four levels to full utilization of new findings

Through systematic, reliable and valid empirical exploration new facts can successfully defend themselves against de facto truths and established dogmas. But that involves constant maneuvering against the Semmelweis reflex which actively rejects any new notions.

Later, when the new evidence is approved and incremental research conducted to progress theoretical thinking (hypothetic-deductive approach), fundamental understanding can emerge.

This process well suites the Semmelweis case. With Semmelweis, the fundamental understanding emerged some twenty years later after Ignaz’s empirical findings, when Louis Pasteur identified the bacteria responsible for causing the child fever.

Applications to data-driven organizations

It shouldn’t be hard to see the relevance of Semmelweis reflex for the development of data-driven driven organizations. In short, being data-driven and making data-informed decision requires giving up on decision making based on seniority, intuition or tradition.

It means that anybody who want’s to champion decision making based on data, will have to acknowledge that there will be strong resistance, a reflex, against data that opposes established opinions. Many HiPPOs will fall before the reflex is taunted.

Organization change is challenging also for reasons other than Semmelweis reflex. Resistance to change is a normal reaction, resulting in fallback to established habits and ways of working. Data-driven approach requires both

  1. acceptance of the facts instead of intuitively appealing ideas
  2. changing the way decisions are made, possible the whole management process

What you as a data advocate can do is to articulate and justify your case with as honest and reliable data as possible. Find numbers to stand for the null hypothesis (the present) state and similar evidence that can reveal a better future. Acknowledge the cultural evolution model from Kohavi and accept that convincing data must make the change happen. You should  seek for understanding the reasons behind the numerical effects, but realize it is really the third, not the second step.

Text: Lassi A Liikkanen, Data-Driven Design Specialist, SC5

Images: public domain, ibid.

The semmelweis reflex was brought to my attention by the delightful presentation from Ronny Kovahi. This story is a tribute to him, a thanks for sharing information while he’s still alive!



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