A friend of mine was diagnosed with a form of dementia. I remember him telling me that some days he thought, “This is just a clinical diagnosis. There is no blood test or MRI. I think they got it wrong.” This led me to think about the diagnosis of abuse. It too is a clinical diagnosis. Because of this, counselors and advisors need to be careful in making the diagnosis. We must be disciplined to avoid asserting the consequent or falling into various cognitive biases.
With this in mind I did a google search for “clinical
diagnosis and asserting the consequent.” AI produced the following summary of information
available. I found it extremely helpful. Those who are helping victims identify
abuse must be cautious. Cognitive biases can prevent identifying abuse or can
cause a wrongful accusation to be attached to an innocent individual. Below is
the information produced by AI.
When making a clinical diagnosis, "asserting the
consequent" is a logical fallacy where a clinician incorrectly assumes
that because a certain symptom or sign is present, a specific disease must be
the cause. This flawed reasoning can lead to misdiagnosis because many
different conditions can cause the same symptom.
Understanding asserting the
consequent
This fallacy, also known as "affirming the
consequent," takes the following logical form:
- Premise
1: If
a patient has disease A, then they will show symptom B.
- Premise
2: The
patient has symptom B.
- Flawed
Conclusion: Therefore,
the patient has disease A.
This reasoning is invalid because symptom B is a consequence
that can have other possible causes. The truth of the consequent (symptom B)
does not guarantee the truth of the antecedent (disease A).
A medical example
- Premise
1: If
a patient has the flu (A), they will have a fever (B).
- Premise
2: The
patient has a fever (B).
- Flawed
Conclusion: Therefore,
the patient has the flu (A).
This is a fallacy because other illnesses, such as
bronchitis, or even a drug reaction, can also cause a fever.
How asserting the consequent
leads to diagnostic error
In clinical practice, the diagnostic process involves
complex reasoning under conditions of uncertainty. Asserting the consequent is
one of several cognitive biases that can interfere with this
process.
It can manifest in the following ways:
- Confirmation
bias: This
is a closely related cognitive error where a clinician forms an initial
hypothesis and then unconsciously seeks out or overemphasizes evidence
that confirms it, while ignoring or downplaying contradictory information.
A clinician might anchor on an early finding, such as a patient's
self-report of a symptom, and then use the fallacy of affirming the
consequent to justify their initial, and potentially incorrect, diagnosis.
- Availability
bias: A
recent or dramatic case can increase the mental "availability"
of a certain diagnosis. A clinician might overemphasize the possibility of
a particular condition simply because they recently saw a similar case,
even if the symptoms could have multiple causes.
- Premature
closure: This
error occurs when a clinician seizes on a potential diagnosis and stops
considering other possibilities. For example, if a patient with a known
history of migraines reports a severe headache, a physician might
prematurely conclude it is another migraine attack, even though the
symptoms could signal a more serious condition like a subarachnoid
hemorrhage.
How to overcome this fallacy in
clinical diagnosis
Several strategies can help clinicians avoid asserting the
consequent and other cognitive biases:
- Differential
diagnosis: Explicitly
generate a list of alternative diagnoses that could explain the patient's
symptoms. This forces a consideration of other possibilities and
discourages premature closure.
- Metacognition
and reflection: Intentionally
slow down the reasoning process, especially in complex or uncertain cases.
Reflective reasoning involves taking time to analyze and question initial
assumptions, rather than relying solely on automatic, intuitive thinking.
- Consider
disconfirming evidence: Actively
look for evidence that might disprove the initial hypothesis. Instead of
seeking only confirmatory data, a clinician can ask themselves, "What
would make me change my mind about this diagnosis?".
- Seek
peer consultation: Discussing
challenging cases with colleagues or seeking a second opinion can provide
an alternative perspective and reduce the influence of individual biases.
- Use
structured tools: For
high-stakes decisions, checklists and evidence-based clinical decision
tools can help ensure a systematic approach and reduce the chance of
cognitive error.
https://www.aafp.org/pubs/afp/issues/2011/1101/p1042.html
