Mr Brown drives the community bus daily from the aged care home to the local RSL.   He has come to see you reluctantly as he has welcomed the magical 75th birthday and received a reminder that he requires a license medical.   ‘But Doc, I’ve been driving for 60 years and never had an accident, surely we’ve both got better things to do than more paperwork?’  You agree in part. Mr Brown is fit and well, he is a compliant patient, but you know it is important that the paperwork be done.  On checking Mr Brown’s unaided vision, you (and he) are surprised to find that he is struggling to manage to read the 6/12 line with either eye?

‘Doc, I had no idea it was that bad – my vision was fine when I had it checked two years ago.’

How often do you have your ‘clinical vision’ checked?  As clinicians we combine what we know from our relationships with our patients, our knowledge of the practice and broader community, our clinical knowledge, and ultimately our ‘gut feel’ – to make our diagnoses.  There is a risk to this technique.  As much as this information synthesis can guide us to a diagnosis, it can also guide away from one – this is cognitive bias.

I’ve been thinking about this topic a lot, particularly in the lead up to the next college exams, as I’ve been working with doctors to explore their clinical decision-making and how best they can demonstrate that reasoning on paper.   With ten weeks to the exam, I’m going to explore one cognitive bias each week, post my thoughts, and follow-up with a clinical reasoning challenge on my Facebook page.  Feel free to make comments on the challenge and share with colleagues.  Send a request to join group

There are enough cognitive biases associated with medical decisions that Cochrane has completed a systematic review of them.  The top four cognitive biases or personality traits influencing clinical decisions were:
1.  Anchoring bias
2.  Information and availability biases
3.  Overconfidence
4.  Lower tolerance to risk

These biases were associated with inaccuracies in diagnosis and sub-optimal management in 36.5% – 77% of cases!

Here are some other common biases:wordcloud-1.jpg

We will have little hope of ‘seeing’ these biases in our practice, unless we deliberately think about them a little more – so lets start with Anchoring Bias.

Anchoring bias is the tendency to to remain with the initial impression or diagnosis even as new information becomes available.  Anchoring bias is often combined with premature closure (tendency to only seek as much information as required to confirm our initial diagnosis).


“If it looks like a duck, walks like a duck and quacks like a duck, then it just may be a duck”  (Walter Reuther)

BUT – It could be a dragon doing a duck impersonation!


For example:

It’s after 5pm on a Friday afternoon and you still have to complete your paperwork before picking up your children from daycare before 6pm.   You call in your final patient, 19 year old engineering student Phillip.  “Doc, I just need a medical certificate as I was too unwell with the ‘flu’ to do an exam today”.

Sudden onset 
Sore throat √                                                =                                   INFLUENZA 
High fever √                                                            (Symptomatic relief spiel and certificate)
Dry cough √                                                            (“Come back if you’re no better Monday”)      Aches and pains √                                                     
Patient is normally fit and well.
Examination:  Temp 39°C, HR 140bpm, RR 16, BP 110/70 mmHg, Red throat, cervical lymphadenopathy, CVS and Respiratory examinations unremarkable.

Thank goodness for an ‘easy’ patient to finish up with.  But did you see those little petechiae developing on his abdomen?   Luckily his medical student girlfriend did when he arrived home…

As our clinical experience increases and we have more ‘illness scripts’ to draw on, our consulting becomes more efficient, for the most part due to pattern recognition.  Hence the importance of being aware of our cognitive biases, so that we don’t miss an impersonating dragon.  I challenge you this week to contemplate the situations in which the dragon’s might be hiding, because if you’re not looking for them, they’ll never be seen!

Anchoring Bias With Critical Implications. AORN Journal, 103(6), 658. doi:10.1016/j.aorn.2016.03.012

Mo, Cognitive errors in medicine:  The common errors. Featured in First Ten EM [Blog post].  Retrieved  from

Saposnik, G., Redelmeier, D., Ruff, C. C., & Tobler, P. N. (2016). Cognitive biases associated with medical decisions: a systematic reviewBMC Medical Informatics and Decision Making16, 138.




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