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I’ve been sick for two days. I have a runny nose, headache, cough and I’m tired.
We agreed that it was very unpleasant having these symptoms when you are moving boxes around a warehouse all day. I examined him and found signs of an upper respiratory tract infection but nothing worse. Now comes the crucial part. If you are a doctor what do you say in the circumstances? You must have your speech ready because you will almost certainly consult someone like this every day, probably more than once a day. In an essay published in the BMJ Trisha Greenhalgh and colleagues wrote:
Evidence users include clinicians and patients of varying statistical literacy, many of whom have limited time or inclination for the small print. Different approaches such as brief, plain language summaries for the non-expert (as offered by NICE), visualisations, infographics, option grids, and other decision aids should be routinely offered and widely used. Yet currently, only a fraction of the available evidence is presented in usable form, and few clinicians are aware that such usable shared decision aids exist. BMJ 2014
What she appears to be hinting at is that words are not enough and may not efficiently convey what this man needs to make a decision for himself. He has already decided for whatever reason that he needs to see a doctor. He was probably able to ‘self-care’ by taking ‘over the counter’ symptomatic measures. Setting aside the notion that he might have presented to get a medical certificate to claim time off what else may be on his agenda? If we postulate that he might want prescribed medicines believing that they will hasten this recovery then there is the prospect of a disagreement with you as the ‘evidence’ suggests otherwise. He probably has a viral illness. But as David Spiegelhalter and colleagues wrote in Science:
Probabilities can be described fluidly with words, using language that appeals to people’s intuition and emotions. But the attractive ambiguity of language becomes a failing when we wish to convey precise information, because words such as “doubtful,” “probable,” and “likely” are inconsistently interpreted. Science 2011
What the person with the cold needs to know is that we cannot be sure what precise ‘bug’ has caused his symptoms. That the most likely cause is a virus but that his symptoms now do not predict the duration or severity of his illness. However most people get better within 10 days and he is probably suffering the most he will through this illness today. The worst symptoms are those he now describes. the cough may linger for a couple weeks. Symptomatic treatment might help him feel better and that people who have been prescribed antibiotics do not get better any faster (that last bit is my team’s research which hasn’t yet seen the light of day in a peer-reviewed journal). However he may not factor all of this information into his thinking without pictures. We need to consider how he makes the decision to take your advice. Scientists have studied this and come up with some helpful advice recently. For a start the patient is unlikely to make a decision based on logic alone.
Behavioral economic studies involving limited numbers of choices have provided key insights into neural decision-making mechanisms. By contrast, animals’ foraging choices arise in the context of sequences of encounters with prey or food. On each encounter, the animal chooses whether to engage or, if the environment is sufficiently rich, to search elsewhere. Kolling et al
There are three treatment options; prescribe an antibiotic now, defer prescribing for a couple days or prescribe nothing. The latter is the appropriate course however a goal in this situation is to reach consensus with this person. To present the data to him in a way that engages his entire decision making apparatus. You are able to usher him out the door without anything only to find that he has lost faith in you. How he feels about the matter is critical:
A few years ago, neuroscientist Antonio Damasio made a groundbreaking discovery. He studied people with damage in the part of the brain where emotions are generated. He found that they seemed normal, except that they were not able to feel emotions. But they all had something peculiar in common: they couldn’t make decisions. The big think
The more challenging approach is to communicate respectfully, appropriately and effectively. Pictures can now assist as never before. Yet the habit of using pictures is neither taught nor practised consistently in clinics. Spiegelhalter again:
The most suitable choice of visualization to illustrate uncertainty depends closely on the objectives of the presenter, the context of the communication, and the audience. Visschers et al. concluded that the “task at hand may determine which graph is most appropriate to present probability information” and it is “not possible to formulate recommendations about graph types and layouts.” Nonetheless, if we aim to encourage understanding rather than to just persuade, certain broad conclusions can be drawn, which hold regardless of the audience.
His team’s recommendations:
- Use multiple formats, because no single representation suits all members of an audience.
Illuminate graphics with words and numbers.
- Design graphics to allow part-to-whole comparisons, and choose an appropriate scale, possibly with magnification for small probabilities.
- To avoid framing bias, provide percentages or frequencies both with and without the outcome, using frequencies with a clearly defined denominator of constant size.
- Helpful narrative labels are important. Compare magnitudes through tick marks, and clearly label comparators and differences.
- Use narratives, images, and metaphors that are sufficiently vivid to gain and retain attention, but which do not arouse undue emotion. It is important to be aware of affective responses.
- Assume low numeracy of a general public audience and adopt a less-is-more approach by reducing the need for inferences, making clear and explicit comparisons, and providing optional additional detail.
Interactivity and animations provide opportunities for adapting graphics to user needs and capabilities.
- Acknowledge the limitations of the information conveyed in its quality and relevance. The visualization may communicate only a restricted part of a whole picture.
- Avoid chart junk, such as three-dimensional bar charts, and obvious manipulation through misleading use of area to represent magnitude.
- Most important, assess the needs of the audience, experiment, and test and iterate toward a final design.
The last offers a call to arms for innovators.
Picture by Alan