Clinical bias can affect the validity and reliability of diagnosis and one thing that can cause clinical bias is when a patient is labelled with having a particular disorder. Labelling theory usually refers to how a label can affect the individual being labelled, but it is also used to explain how others can treat someone based on their label.
Effects of labelling: Confirmation bias can explain some biases in diagnosis related to labelling. Studies have shown that if a patient is given a label (i.e. a diagnosis of a particular disorder) when others are asked to make a diagnosis they are more likely to make the same diagnosis, possibly because of confirmation bias – they are seeking out and focusing on the information that is consistent with the original label. In other words, the label is biasing their perception and processing of information when making the diagnostic judgement.
This can be seen in Temerlin’s classic study.
- Key Study: Confirmation bias: why psychiatrists stick to wrong preliminary diagnoses (Mendel et al. 2011)
- Exam Question Bank: Paper 2: Abnormal Psychology
Key Study: Effects of labelling on diagnosis (Temerlin, 1968)
In this study, the researchers showed a video tape to their participants (psychiatrists, clinical psychologists and graduate students in clinical psychology). In the video, an actor portrayed a mentally healthy scientist and mathematician. The subject of the video involved the actor discussing a book about psychology he had read and how he wanted to discuss it with a psychologist.
- Experimental condition: participants were told that an experienced psychiatrist had said the man was a “very interesting man because he looked neurotic, but actually was quite psychotic” (meaning he had a disorder).
- Control group #1: participants were given no prior information
- Control group #2: participants were told he was mentally healthy.
After watching the video, the participants were asked to make a diagnosis. They were given 30 choices that included a range of disorders and general personality types (non-disorders). The correct choice was normal or healthy personality, which was one of the options. However, 60% of the psychiatrists in the experimental group selected a psychotic disorder, as did 28% of the psychologists and 11% of psychology graduate students. By comparison, no one in the control groups chose a diagnosis of a psychotic disorder. These results suggest that any label already given to a patient can affect their follow-up diagnosis, which can be explained by the effects of confirmation bias. This has implications for how clinicians go about using multiple people for accurate diagnosis.
Some conclusions that we can draw from this study:
- Clinical bias: This is more likely to occur if clinician’s are aware of a diagnosis that has already been made by someone else.
- Validity/reliability of diagnosis: This can be affected by clinical and confirmation bias – someone else’s wrong diagnosis could lead to further incorrect diagnoses because of the effects of the label.
- Normality/abnormality: Clinical bias is one factor that can make it difficult to distinguish normality from abnormality.
- Biases in thinking and decision making: The above study provides an example of one bias, confirmation bias – diagnostic labels can lead to confirmation bias.
- The IB often uses the phrase “the role of (….x…) in…(…y…)” This can be confusing language, so you can just think of any question like this as asking how (….x….) influences (…y…).
- For this topic, you need to be able to explain how clinical bias can influence diagnosis, using studies to support your answer.
- The example of confirmation bias here could be used as one bias in thinking and decision making in the cognitive approach. It would make for an excellent addition to an essay about biases.
Temerlin, M. (1968). Suggestion Effects in Psychiatric Diagnosis. The Journal of Nervous and Mental Disease, 147, 349-353.
Travis Dixon is an IB Psychology teacher, author, workshop leader, examiner and IA moderator.