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Lecture 1: Risk and decision-making

The way we make a decision is influenced by how we subjectively conceive an option.
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Welcome back to the course Brain, Behaviour, and Dentistry. Now we will back to the fourth session of the course. After this class, you will learn the concepts of risk and recognize the theoretical framework of decision-making under risk. In our last class, I mentioned that making a medical decision is complicated because of its uncertain nature. One just cannot guarantee the benefits from treatment for all patients. There is always uncertainty in the outcome of treatment. Therefore, medical decisions are decisions under risk, here ‘risk’ does not mean an unwanted side effect, but highlights such uncertainty. For example, according to the weather forecasts, there is 99% or 1% of the chance to get a rainy day tomorrow.
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In both conditions, we are very sure that tomorrow will or will not be a rainy day, respectively. Both conditions are not risky because it is highly predictable. The most risky or uncertain condition will be 50% of the chance to get it rainy – that means half and half, the weather is highly unpredictable. Interestingly, patients may show a great variation in their tolerance of such uncertainty. For example, when knowing that a treatment may work with a success rate of 90%, some patients may still feel worried that ‘it may fail anyway’. While some patients would feel comfortable when knowing the success rate is 60%, just greater than the chance of flipping a coin!
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The concept of ‘intolerance of uncertainty’ reveals a complicated association between the judgement of risk and personality trait.
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Since making medical decisions involves the judgment of risk, it is not surprising that human beings make a decision by considering both the outcome benefits and the probability to have an outcome. According to the prospect theory by psychologist and economist, Tversky and Kahneman, people evaluate different options by considering the value and weight of an option, which is constructed subjectively. That means the way we make a decision is influenced by how we subjectively conceive an option. Such a human decision can be different from the choice from a computer, which simply calculates the expected value of an option. We will discuss the prospect theory further. According to prospect theory, people may prefer some options because they have a higher weight, the decision weight.
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The decision weight is defined as the psychological impact of the stated probability of an outcome’s occurrence. It should be noted that such an impact is not always in proportion to the stated probability, such as the rate of treatment success documented by research papers.
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For example, one treatment may have a success rate of 20% and another 80%. Objectively, the success rate is four times in the second treatment. However, the frequency for patients to choose the second treatment is not exactly four-time of the first one. That is to say, the impact of the increase in probability may vary. In fact, Tversky and Kahneman found that the decision weight, as a function of the stated probability, shows a non-linear relationship with the stated probability. According to many experimental data conducted in different scenarios, they found that people show a tendency of overweighting a very low probability and underweighting a very high probability. This may explain why patient-dentist communication is difficult.
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While dentists prefer to discuss on the basis of stated probability, patients make decisions according to the impact they feel about the stated probability.
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Prospect theory is a descriptive theory because it represents how people actually make decisions, rather than telling people how to make the best decision. If we want to achieve a good decision, reasonably, we need to balance all the gain and loss from an option. This would be what a computer really does. However, when judging gain and loss, people have different tendencies. We tend to feel a stronger unpleasantness toward loss. For example, the subjective value for gaining 1000 dollars is good. However, losing 1000 dollars is more hateful and there’s a stronger motivation for us to avoid such a loss.
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Therefore, if you are asked to draw a lottery with winning and losing 1000 dollars at the same rate, you won’t feel it too attractive. The expected value for such a lottery is zero, and we would prefer just nothing to happen. If we draw the lottery, it is possible that we may lose 1000 dollars – such a feeling of loss is so hateful that we don’t want it, even though there is the chance to get 1000 dollars. The phenomenon is named loss aversion, which literally means we tend to avoid loss, even the loss can be balanced. This could be another reason why patient-dentist communication is difficult. Dentists think that the benefits and adverse effects of treatment are balanced.
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However, patients’ decisions may be strongly influenced by the dark side, such as the occurrence of an adverse effect or the cost of treatment, and their choices may reflect a tendency to avoid it.

Risk?

In this step, you will learn the concepts of risk and recognize the theoretical framework of decision-making under risk.

There is always uncertainty in the outcome of treatment. So all the medical decisions are ‘at-risk’ decisions. However, ‘risk’ does not mean an unwanted side effect, but highlights such uncertainty.

Another reason why patient-dentist communication is difficult is people tend to avoid loss, even the loss can be balanced.

We aren’t like a computer, which can analyze all the gains and losses from an option, and try to figure out the best way to balance them all. So patients’ decisions may be strongly influenced by the dark side, such as the cost of the treatment and the bad experience they had while they were kids.

Hence, what can we do to help ourselves when we need to make a medical decision? And what would we expect our dentists to do to help us make a fair desicion? And being a dentist, what will you do to provide a better view for your patients?

We would like to learn more from you.

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Brain, Behaviour, and Dentistry

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