Emergency medicine and paramedicine, one can argue, are highly cognitive professions. One of the pitfalls to this specialty however is the level of risk involved.

Medical error is the 6th leading cause of death in North America, and some studies have shown that cognitive error or some flaw in decision making – as opposed to lack of knowledge – is present in about 95% of cases where there was a medical error. MoreoverThe most recent institute of medicine report says, that as a patient, it’s not if you’ll be subjected to a diagnostic error, but when.

Dr. Vanessa Bohn is a Pediatric Emergency Medicine physician at the Children’s Hospital of Eastern Ontario (CHEO). She graduated from the Royal College of Surgeons in Ireland in 2013. Dr. Bohn then completed her pediatric residency at the Northern Ontario School of Medicine (NOSM) in Thunder Bay, Ontario. She was the chief resident of the pediatrics program from 2015-2016. In 2016, Dr. Bohn started fellowship in pediatric emergency medicine at the CHEO. During her fellowship, she completed a Master in Medical Science of Medical Education at Harvard Medical School. Her academic interests are in all things medical education, curriculum development and how the standardization of clinical practice affects medical learners.

Errors can thus be broken down into 3 subtypes

  • No fault errors
  • Systemic errors
  • Cognitive errors

Cognitive Errors

  • There are hundreds of cognitive errors, and we are particularly prone to cognitive errors when any aspect of  ourreptilian brain is activated, so if we’re hungry, stressed or tired  

To start off, we’re going to consider the Cognitive Reflection Test. The purpose of this test is to measure someone’s tendency to override their gut instinct and be reflective in their thought process. Don’t feel bad if you didn’t do well. These questions are meant to trip you up. The economists who created this test asked a random selection students at MIT, and only 48% got all three questions right. When they asked a random sample of people watching a fireworks display in Boston, only 26% got all three questions right. You’re brain tricks you into making a fast, decision without really examining your thought process.  

  1. A bat and ball cost 1.10$ in total. The bat costs a dollar more than the ball. How much does the ball cost?
  2. It takes 5 machines 5 minutes to make 5 widgets, how long does it take 100 machines to make 100 widgets?
  3. In a lake there is a patch of Lilly pads, every day the patch doubles in size. If it takes 48 days for the patch to cover the entire lake, how long would it take for the patch to cover half the lake?

To further illustrate this:

  1. What is the world’s deadliest animal?
  2. If a coin is tossed 10 times, and the first 9 times it came up heads. Whats the chance of it coming up heads on the 10th toss?

To understand the concept, we must talk about the concept of metacognition. This was developed by two psychologists Daniel Kahneman, who was subsequently awarded a Nobel prize for this work,  and Amos Taversky, who unfortunately passed away before it was awarded.  They developed this concept called dual process theory. Which basically says our brain has two modes of thinking.

There’s System 1 thinking, which is quick, intuitive and automatic, while System 2 thinking are much more reliable, but slower, analytical, effortful, complex, and resource intensive.  Psychologists think we spend about 95% of our time in System 1, which is really dependant on intuition or heuristics, but is prone to error.



Cognitive Bias & Debiasing


While there are hundreds of cognitive biases, but there are some that a bit more relevant for our area of practice.

  • Diagnostic Momentum: The tendency for a particular diagnosis to become established without adequate evidence.
    • Debiasing strategy:
      • Exercise extreme caution in patients that present pre-labelled
      • Especially important at handover
      • Constantly evaluate and re-evaluate
      • Assess patients appropriately.
      • Consciously decide to arrive at your diagnosis or differential diagnosis independent of the labels applied by others.
      • Taking a diagnostic “time out” to reconsider the differential diagnosis may be helpful.
  • Premature Closure: very similar to diagnostic momentum, but premature close bias happens when we adopt a diagnosis without appropriate evidence, whereas diagnostic momentum involves several individuals. 
  • Confirmation Bias: when we look for and selecting data that supports a particular hypothesis, and ignores information that disproves your hypothesis
    • Debiasing strategy:
      • Deliberating looking for data that refutes that hypothesis


  • Search Satisfying: The tendency to call off a search once a finding has been made
    • Debiasing strategy:
      • Look for additional findings once the first finding has been made
      • “The most common missed fracture is the second fracture”
  • Gambler’s Fallacy: When we experience an unusualrun of independent events, and we believe it lowers the probability of a subsequent event
    • Debiasing strategy
      • When unusual runs or sequences are experienced, remind yourself of the laws of probability 
  • Hindsight Bias: when a situation is re-evaluatedin retrospect, it’s impossible to be objective about what decisions you would’ve made at that time if you were in that position  
    • Be kind to one another and your colleagues. Don’t judge too harshly the decisions that were made in a specific situation and context. All we can do is identify errors, try and learn from them and prevent them from happening again
  • Bounded Awareness: Overlooking critical, easily accessible and relevant information

  • Anchoring Bias: Focusing on one particular symptom, sign, or piece of information, or a particular diagnosis early in the diagnostic process and failing to make any adjustments for other possibilities — either by discounting or ignoring them. May lead to premature closing of thinking
    • Debiasing strategy
      • Avoid early guesses
      • Delay forming an impression until all information is gathered