1. CRITICAL THINKING IN CLINICAL
DECISION MAKING
DR. CHEW KENG SHENG

2. Question #1
• Jack is looking at Anne,
but Anne is looking at
George. Jack is married,
but George is not. Is a
married person looking
at an unmarried person?
A. Yes
B. No
C. Cannot be determined

3. Disjunctive Reasoning
• Would you have answered differently if
the options are only Yes or No?
• This thought process is called fully
disjunctive reasoning – reasoning that
considers all possibilities
• Most people can carry out fully disjunctive
reasoning when they are explicitly told
that it is necessary but most do not
automatically do so.

4. Discuss further
What if this is a clinical case?
Does it make a difference in your decision
making process if you have only option A
and option B as compared to if you are
given option C as well (which essentially is
a permission or excuse not to make a
definite choice on the basis of “inadequate
information given”)?

5. “Humans are cognitive misers
because our basic tendency is to
default to the processing
mechanisms that require less
computational effort, even if they are
less accurate” – Keith Stanovich,
cognitive psychologist

6. Question #2
• Suppose you want to
buy a book and a
pencil. The book and
the pencil cost
RM1.20 in total. If the
book costs RM1.00
more than the pencil,
how much does the
pencil cost?

7. Discuss further
• Discuss on intelligence vs Rationality
• “We often assume intelligence and
rationality go together but we shouldn’t be
surprised when smart people do foolish
things” – Keith Stanovich
• Dysrationalia – is the inability to think and
behave rationally despite having
adequate intelligence

8. What does the middle character look like?

9. Which line is longer?

10. How do we make decisions?
• Decision making is one of the most
important we do, it is the engine that
drives our behavior.
• We make many decisions continuously in
the course of our waking hours. These
decisions vary in complexity
• Some are relatively simple, automatic
process, well-rehearsed. Some have
consequential implications – like choosing
our life-partners

11. “What we are, or how we live our lives
are largely determined by the
decisions we made”
“We first make our choices, then our
choices make us”

12. How do we make decisions?
• One of the major developments in
cognitive psychology over the last 20
years is the dual process theory (DPT) of
reasoning.
• The DPT of reasoning has emerged as
the dominant theory of reasoning
particularly through the works of people
like Epstein, Tversky and Kahneman,
Stanovich and West, and Evans.

13. Dual-process thinking
• According to the DPT of reasoning, there
are two modes of decision making, i.e.,
System 1 and System 2.
• System 1 is the fast, intuitive, reflexive,
automatic and frugal thinking and it is
where we spend most of our time making
most of our decisions. Driving a car for
someone who has been driving for a long
time is an example of System 1 thinking.

14. Dual-process thinking
• System 2, on the other hand is a
deliberate, analytical, purposeful or
effortful form of thinking that is usually
slower.
• Discuss: give further examples of some of
the decisions that you make in your daily
lives that are largely based on System 1
and those that are based on System 2

15. Dual-process thinking
System 1 (Intuitive) System 2 (Analytical)
Experiential-inductive Hypothetico-deductive
Heuristic Systematic
Pattern recognition Robust decision making
Unconscious thinking theory Deliberate, purposeful
thinking
Fast Slow
High capacity Limited
High emotional attachment Low emotional attachment
Low scientific rigor High scientific rigor

16. Case illustration #1

17. Case illustration #2
This child develops this rash after 5 days of antibiotics for fever
and cough. The resident takes a quick glance of this child and
diagnose him with Stevens-Johnson syndrome. He says that he
has seen a similar case before when he was a house officer and
he remember that case very well because the child died later on.

18. Was the resident right?
• The resident employed System 1 thinking
• Quick, intuitive, pattern recognition based
on what he has seen before
• High emotional association – his previous
patient died following a ‘similar case’
• But was he right?
• SJS often has extensive mucosal
involvement. SSSS usually does not.
• Nikolsky’s sign is usually present in SSSS

19. Heuristics
• Although System 1 is the fast, reflexive
thinking mode that we commonly used,
inherent to the intuitive nature of this
system, it often requires the use of
heuristics.
• Heuristics are mental shortcuts or “rules
of thumb” or “gut-feeling” used to assist
us to rapidly make decisions without
formal analysis.

20. Heuristics
• Two heuristics that are considered
essential for a clinician when faced with
an emergency situation are the “rule-out-
worst-case-scenario” and the sick/not sick
dichotomy

21. RECOGNIZED
Pattern
Patient Pattern Recognition Executive T Dysrationalia
Presentation Processor override override Calibration Diagnosis
Repetition
NOT
RECOGNIZED

22. System 1 and System 2 in play

23. Cognitive biases
• While heuristics are helpful cues for
System 1, at times, they are prone to
cognitive biases and errors.
• Cognitive biases or cognitive disposition
to respond are our predictable
tendencies to respond in a certain way to
the contextual clues at that time
• These biases are often unconsciously
committed, and may result in flawed
reasoning

24. Availability bias
• Availability bias – this refers to our
tendency to judge things as being more
likely, or frequently occurring, if they
readily come to mind.
• Therefore, a recent experience with a
particular disease, for example, thoracic
aortic dissection may inflate likelihood of
a clinician to diagnose the patient with
this disease every time when the clinician
sees a case of chest pain.

25. Anchoring
• Anchoring – this refers to our tendency to
fixate our perception on to the salient
features in the patient’s initial
presentation at an early point of the
diagnostic process so much so that we
fail to adjust our initial impression even in
light of later information.

26. Confirmation bias
• Confirmation bias – this refers to our
tendency to look for confirming evidence
to support the diagnosis we are
“anchoring” to, while downplaying, or
ignoring or not actively seeking evidences
that may point to the contrary.

27. Confirmation bias
• Confirmation bias often goes together
with anchoring. For example, if a clinician
has anchored or fixated the diagnosis of
myocardial infarction in his mind, he will
have the tendency to look for evidences
to support this diagnosis, say, ST
segment elevation on electrocardiography
even if the amount of elevation is very
minimal.

28. Confirmation bias
• In contrast, if the patient’s chest X-ray
demonstrates a widened mediastinum
width with unequal pulses on examination
and high blood pressure, the clinician
may have ignored such important cues
that may point to the life threatening
condition of thoracic aortic dissection.

29. Search satisficing
• This refers to our tendency to stop
looking or call off a search for a second
diagnoses when we have found the first
one.
• This bias can prove to be detrimental in
polytrauma cases.

30. Search satisficing
• A classic example of this bias is the
tendency of the physician to call off the
search for a second fracture once he
thinks he is “sufficiently satisfied” with
finding the first fracture of medial
malleolus, when in fact, the patient may
have sustained Maisonneuve fracture
with a second proximal fibula fracture.

31. Case illustration #3
This patient claimed to have
twisted his left ankle and
complained of severe ankle
pain. The medical officer in
the A&E ordered an X-ray
of that ankle. He saw some
abnormalities over the
medial malleolar region and
then referred the case to the
orthopedics.
Question: Do you agree with his plan of management? Give
your comments.

32. Normal mortise view

33. Normal mortise view
• The entire mortise joint space should be
of uniform width, ≤ 4 mm (light gray).
• The distal tibiofibular joint (dark gray)
should be only slightly wider than the
mortise joint space, ≤ 5.5 mm.
• The tibiofibular overlap should be > 1 mm
on the mortise view.

35. An example of search satisficing
A Maisonneuve fracture should be
suspected whenever there is a
fracture to the medial aspect of the
ankle or widening of the distal
tibiofibular joint
Always remember the adage in X-
rays of #:
“One joint below, and one joint
above”

36. Triage cueing
• This is basically a form of anchoring
where once a triage tag has been labelled
on a patient, the tendency is to look at the
patient only from the perspective of the
discipline in which the patient is tagged
to.

37. Diagnostic momentum
• Once diagnostic labels are attached to
patients they tend to become stickier and
stickier. Through intermediaries,
(patients, paramedics, nurses,
physicians) what might have started as a
possibility gathers increasing momentum
until it becomes definite and all other
possibilities are excluded.

38. Sunk cost fallacy/bias
• The more a clinician invest in a particular
diagnosis, the less likely he is to release it
and consider alternatives. This form of
entrapment is common in financial
investment. In clinical setting, the time
mental energy, and for some, the ego
may be a precious investment to let go.
Confirmation bias maybe a manifestation
of such unwillingness to let go of a failing
diagnosis.

39. Sunk cost fallacy/bias

40. Ego bias
• This refers to our tendency of
overestimating the prognosis of one’s
own patients compared to that of a
population of similar patients under the
care of other physicians.

41. Blind spot bias
• This refers to the bias that many people
have where they believe that they are
less susceptible to errors compared to
others. This has some similarities with
ego bias.

42. Hindsight bias
• This bias typically occurs during morbidity
and mortality meetings where the
outcome of the case is already known.
• With hindsight bias, a case with a bad
outcome is judged negatively where the
sequence of decisions made leading up
to the outcome must be bad as well.

43. Hindsight bias
• However, it is not necessarily true that
just because the outcomes are bad, the
decisions are bad too, as people
generally do not deliberately make bad
decisions.
• The decisions taken at that time must
have made sense to them.

44. Hindsight bias
• Furthermore, the process of cognitive
autopsy during morbidity and mortality
meetings are devoid of the ambient
context (e.g. a busy working emergency
department) and the affective dispositions
(e.g. the stress, sleep-deprived or
depressed nature of the doctor) in which
the decision was made during that
particular time.

45. Overconfidence bias
• It refers to our universal tendency to
believe that we know more than we do.
• Overconfidence reflects a tendency to act
upon incomplete information, intuitions, of
hunches.

46. Gambler’s fallacy
• The concept of this bias is borrowed from
the gambling situation where if a coin is
tossed ten times, and for every case of
the toss, head is shown.
• A person with gambler’s fallacy will say
that if the coin is tossed for the 11th time,
there must be a greater chance of being
tail.

47. Gambler’s fallacy
• However, the coin has no memory and
the coin actually has a 50-50 chance of
showing tail in each toss, which is
independent of the previous outcomes.

48. Gambler’s fallacy
• An example of this fallacy can happen
when a clinician see five cases of
shortness of breath in the course of a
working shift, and in each case, the
patient turns out to be having pneumonia.

49. Gambler’s fallacy
• When the 6th patient with shortness of
breath arrives in the emergency
department, a clinician with this fallacy
will probably think that for this 6th time,
the patient must be having a condition
other than pneumonia, such as asthmatic
attack.

50. Posterior probability error
• This is the opposite of gambler’s fallacy.
In this bias, if a clinician sees five patients
with shortness of breath in the course of a
working shift, which turn out to be
pneumonia in every cases; when the 6th
patient with shortness of breath arrives in
the emergency department, the tendency
is to believe that this patient must be
having pneumonia as well.

51. Summary of common cognitive biases (1)
Cognitive bias Thought process
Availability bias “I remember seeing a similar
patient with diagnosis X.
Therefore this patient must be
having diagnosis X”
Anchoring bias “From the very offset, it seems
that this patient is having
diagnosis X, so, he must be
having diagnosis X”
Confirmation bias “Since this patient has diagnosis
X, I must look for evidence to
support that this patient has
diagnosis X”
Search satisficing “I have found diagnosis X in this
patient and I am happy with it!”

52. Summary of common cognitive biases (2)
Cognitive bias Thought process
Triage cueing “The triage officer found that the
patient has diagnosis X. Let’s
treat the patient as having
diagnosis X”
Diagnostic momentum “The HO says the patient has
diagnosis X. The MO says the
patient has diagnosis X. The
specialist says the patient has
diagnosis X. And nobody is
challenging it”
Sunk cost fallacy “I have invested so much of my
time and energy in managing this
patient as having diagnosis X.
What else could it be?”

53. Summary of common cognitive biases (3)
Cognitive bias Thought process
Gambler’s fallacy “I have seen the last 5 patients
with diagnosis Y. This time, this
patient must be having diagnosis
X”.
Posterior probability error “I have seen the last 5 patients
with diagnosis Y. This time, this
patient must be having diagnosis
Y as well”.
Ego bias “Statistically speaking, my
patients often do better than
patients from the other team!”
Blind spot bias “This kind of mistakes often
happen to Dr. X’s patients. I
wouldn’t have made such
mistakes”

54. Cognitive biases categories
• Biases due to over-attachment to a
particular diagnosis
– Anchoring, confirmation bias
• Biases due to failure to consider other
diagnosis
– Search satisficing
• Biases due to inaccurate estimation of
prevalence
– Availability bias, gambler’s fallacy, posterior
probability error

55. Cognitive biases categories
• Biases due to the way the patient is
presented
– Triage cueing
• Biases due to inheriting someone else’s
thinking
– Diagnostic momentum
• Biases due to physician’s personality and
affect, decision style
– Ego bias, blind spot bias

56. Critical Thinking (1)
1. Knowing and understanding the System
1 & System 2 thinking
2. Recognizing the distracting stimuli,
biases and irrelevance affecting our
decisions
3. Identifying, analyzing and challenging
assumptions in arguments
4. Be aware of cognitive fallacies and poor
reasoning

57. Critical Thinking (2)
5. Recognizing deceptions – deliberate or
otherwise
6. Having the capacity for assessing the
credibility of information
7. Understand the need for monitoring and
control of our own thinking processes
8. Be aware of the critical impact of fatigue
and sleep deprivation on decision
making

58. Critical Thinking (3)
9. Understand the importance of monitoring
and control of our own affective states
that influence the quality of our decisions
10. Understand the context under which
decisions are made
11. Capacity to anticipate the consequences
of our decisions

59. Pre-dispositional factors
• Further compounding the difficulty in
clinical decision making is the undeniable
fact that the quality of our clinical
decisions is also influenced by ambient or
environmental conditions under which the
decision is made.
• For example, when faced with a potential
clinical emergency situation, physicians
are often expected to make diagnostic
decisions within a limited time frame.

60. Affective state of the decision maker
• Other factors such as the affective state
of the clinician, general fatigue,
interruptions, distractions, sleep
deprivation etc, can influence the quality
of our decisions too. For example, sleep
deprivation (in the course of a long
working shift, for example) can have a lot
of negative impact, not only to the quality
of the decision making, but to the general
health of the clinician as well.

61. Sleep deprivation
• Sleep deprivation and circadian
dysynchrony can impair performance and
reduce many aspects of human capability
including reduced attention vigilance,
impaired memory, impaired decision-
making, lagged reaction time, impaired
hand-eye coordination and disruptive
communications.

62. Sleep deprivation
• For example, it has been shown that after
17 hours of continuous wakefulness,
hand-eye coordination task would have
declined to such a level equivalent to that
of a blood alcohol level of 0.05%. And at
24 hour of sustained wakefulness, the
impairment in psychomotor function is
equivalent to a blood alcohol
concentration of 0.1%

63. Sleep deprivation
• Furthermore, a fatigued worker will also
have a tendency to slow down work his
work processes in order to maintain
accuracy (known as the “speed-accuracy
trade-off”)

64. De-biasing strategies
• One of the tremendous challenges in
cognitive biases is finding ways to de-bias
them. A de-biasing strategy commonly
used is called the cognitive forcing
strategies. These are deliberate,
systematic self-regulatory cognitive
mechanisms to provide a check and
balance to minimize biases.

65. Metacognition
• An example of cognitive forcing strategies
is metacognition. Metacognition is an
individual’s ability to stand apart from his
own thinking in order to be aware of his
own preferred learning approaches and
ultimately to manipulate his own cognitive
processes to his own advantages.

66. Metacognition
• In short, metacognition is “thinking about
thinking.” It allows one to ask questions
like: “How well did I do?” “What could I
have done it differently if I am given a
chance again?” etc.

67. De-biasing strategies
• But suppose one has the necessary
mindware, then the next question
Stanovich argues would be whether one
actually perceives a need to de-bias
them. But even if the person perceives
the need for de-biasing, the next question
would be whether the de-biasing effort
needed is a sustained effort.

68. De-biasing strategies
• If it is but the person does not have the
capacity for sustained de-biasing, then
the natural tendency is still to fall back
into System 1 of reasoning. This is
because when it comes to choosing the
cognitive strategies to apply for solving a
problem, we generally choose the fast,
computationally inexpensive strategy
(System 1).

69. Cognitive forcing strategies (1)
• One of the ways to minimize the risk of
committing cognitive biases is to forcibly
ask ourselves these few questions
whenever we have made our clinical
decisions (especially if our decision is to
discharge the patient):
1 What is/are the possible life/limb threats
in this patient? Why does the patient
come?

70. Cognitive forcing strategies (2)
2 What if I am wrong? What else could it
be?
3 Do I have evidences for/against this
decision/diagnosis that I've made?
4 What are the ambient/affective factors
that are influencing my decisions?

71. Cognitive forcing strategies (3)
5 In the unfortunate event that this case
landed as a medico-legal case 10 years
down the road, is what I've documented
defensible? (in other words, have I
documented what needs to be
documented, is my writing legible
enough, is the date and time written,
etc).

72. • Download a free article on ‘Making
decision better’ here:
• http://tinyurl.com/cbjvjof

73. Authority gradient
• Another issue that may hamper the
learning and practice of critical thinking is
the issue of authority gradient.
• Authority gradient is defined as the
gradient that may exist between two
individuals’ professional status,
experience, or expertise that contributes
to difficulty exchanging information or
communicating concern.

74. Authority gradient
• Authority gradient is especially prevalent
in our Asian culture - which maybe
heavily influenced by Asian philosophies
of respecting the seniors.
• Such noble value is of course vitally
important in maintaining societal harmony
but can be dangerous if taken to the
extreme and junior doctor adopts an
unhealthy pessimism attitude.