Without evidence of benefit, an intervention should not be presumed to be beneficial or safe.

- Rogue Medic

Confirmation Bias and EMS

The Wikipedia Article of the Day for today/tomorrow, depending on where you are in relation to Wikipedia time, is Confirmation Bias.[1]

This is not the shortest article in Wikipedia, but it is a complex subject. Perhaps a short explanation can be better provided by the full version of the abbreviated quote they provide from Francis Bacon, one sentence at a time.

The human understanding when it has once adopted an opinion (either as being the received opinion or as being agreeable to itself) draws all things else to support and agree with it.[2]


We are all biased.

I do not know of anyone who thinks, but does not have biases.

And though there be a greater number and weight of instances to be found on the other side, yet these it either neglects and despises, or else by some distinction sets aside and rejects, in order that by this great and pernicious predetermination the authority of its former conclusions may remain inviolate.[2]


We tend to believe things that support our biases.

We tend not to believe things that do not support our biases.

And therefore it was a good answer that was made by one who, when they showed him hanging in a temple a picture of those who had paid their vows as having escaped shipwreck, and would have him say whether he did not now acknowledge the power of the gods — “Aye,”[2]

Clearly, if all of these people survived because they prayed to the gods, this is excellent proof of the power of the gods.

. . . or is it?

asked he again, “but where are they painted that were drowned after their vows?”[2]

We do not know how many prayed to the gods, yet still drowned, so we do not have complete information.

What if those who survived only claimed to have prayed to the gods, because that would be the acceptable thing to do under those circumstances?

What if more of those who prayed to the gods drowned than survived?

What if praying to the gods interfered with activities that would have increased their chances of survival? Even if many of those who survived prayed, maybe the praying decreased the number who survived.

Swim this way!

After I pray! (Last words before drowning.)

And such is the way of all superstition, whether in astrology, dreams, omens, divine judgments, or the like; wherein men, having a delight in such vanities, mark the events where they are fulfilled, but where they fail, though this happen much oftener, neglect and pass them by.[2]


There are plenty who defend MAST/PASG, or Trendelenburg position, or flying everyone with auto damage, or claim to be competent at intubation even though their last intubation was months ago on the third attempt and if the patient had not already been dead – that would have finished the patient off, or those who claim that intubation saves lives, or epinephrine raises the dead, or any of dozens of other EMS myths, are always quick to point to the cases they are sure would have died, if not for their magical treatment.

Research, which is designed to minimize the effect of bias (when done properly), does not support these magical treatments.

Some of these may be true, but they are not supported by well done research.

Any claim that these save lives is an example of Confirmation Bias.

Most of these are clearly not true, because this is demonstrated by well done research.

Any claim that is contrary to the good research disproving the efficacy of treatment is an example of Confirmation Bias.

When we look at well done research, we cannot just look at those who survive, we have to include those who do not survive.

In well done research, when we look at those who survive, we need to look at those who survive beyond the doors of the ED (Emergency Department).

If we are including all of the patients dying in the emergency department as survivors, we have a very distorted view of what survival is.

A treatment that only delays declaration of death until arrival at the ED is really only treating the documentation, it is not treating the patient. The only things that change are the location and title of the person pronouncing the patient dead.

But with far more subtlety does this mischief insinuate itself into philosophy and the sciences; in which the first conclusion colors and brings into conformity with itself all that come after, though far sounder and better.[2]


This can be so habitual, that we do not realize it that we are doing it. This is why we need to aggressively try to remove the influence of these biases, when we make important decisions.

Besides, independently of that delight and vanity which I have described, it is the peculiar and perpetual error of the human intellect to be more moved and excited by affirmatives than by negatives; whereas it ought properly to hold itself indifferently disposed toward both alike.[2]


We ignore the ability to learn from our mistakes, when we try to get all of our information to support our biases.

If we do not learn from our mistakes, we get more opportunities to learn from our mistakes.

Our patients may not be lucky enough to survive our mistakes.

If we are going to be making decisions that affect our patients’ lives, we need to be as sure as possible that we are not ignoring more accurate information.

Indeed, in the establishment of any true axiom, the negative instance is the more forcible of the two.


Francis Bacon is not being a cynic. He is only realizing that this bias is a part of human nature. He is realizing that we need to be wary of our tendency to give more value to the information that makes us happy than to the information that, while more accurate, may displease us.

If I touch a flame, I quickly learn that fire can be painful.

Other types of negative feedback may not be as hard to ignore.

If I use a certain treatment and my patient dies, it is easy to make the excuse that the patient would have died anyway. It is easy to come up with an excuse that allows me to avoid learning from my mistakes, even though I am killing patients.

Confirmation Bias is alive and well in EMS.

We need to kill off Confirmation Bias.

We need to question the information we are presented with.

Do I believe that because it makes me feel good, or because there is good evidence to support it?

See also:

EMS Mythology Starter Kit

and warm cuddly bears



[1] Confirmation Bias
Article of the Day

The full quote is no longer at the Wikipedia page, but the link below is to the book and I copied the full aphorism from the site. Update 01/29/2017. I have not changed any of the text, other than to switch to footnotes, provide the correct footnotes, and to correct the YouTube link.

[2] Aphorism 46
Francis Bacon
Novum Organum 1620
Basil Montague, ed. and trans.
The Works, 3 vols. (Philadelphia: Parry & MacMillan, 1854), 3: 343-71
Book at Hanover.edu

46. The human understanding, when any preposition has been once laid down, (either from general admission and belief, or from the pleasure [Page 348] it affords,) forces every thing else to add fresh support and confirmation; and although more cogent and abundant instances may exist to the contrary, yet either does not observe or despises them, or gets rid of and rejects them by some distinction, with violent and injurious prejudice, rather than sacrifice the authority of its first conclusions. It was well answered by him who was shown in a temple the votive tablets suspended by such as had escaped the peril of shipwreck, and was pressed as to whether he would then recognise the power of the gods, by an inquiry; “But where are the portraits of those who have perished in spite of their vows?” All superstition is much the same, whether it be that of astrology, dreams, omens, retributive judgment, or the like; in all of which the deluded believers observe events which are fulfilled, but neglect and pass over their failure, though it be much more common. But this evil insinuates itself still more craftily in philosophy and the sciences; in which a settled maxim vitiates and governs every other circumstance, though the latter be much more worthy of confidence. Besides, even in the absence of that eagerness and want of thought, (which we have mentioned,) it is the peculiar and perpetual error of the human understanding to be more moved and excited by affirmatives than by negatives, whereas it ought duly and regularly to be impartial; nay, in establishing any true axiom, the negative instance is the most powerful.




  1. i was shocked fox news had such old viewers considering all their young, hip ads for walk-in bathtubs and mesothelioma lawyers

  2. What’s worse, stress eating, or the GUILT from stress eating?


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