Lecture 1: Cognitive bias and heuristics

Welcome back to the course Brain, Behaviour, and Dentistry. Now we will be back the fourth session of the course. After this class, you will learn to identify the factors related to decision-making, to distinguish the common cognitive bias and heuristics, and to recognize the association between emotion and decision-making. Here ‘bias’ does not simply mean an error or mistake about the outcome of a decision. What matters is not just the outcome being right or wrong, but also how information is processed. There are many sub-categories of cognitive bias, which distort how information is represented in our mind. For example, our decisions can be influenced by confirmation bias, which means we tend to believe in the value of our previous decisions.

People would look for supporting evidence and develop some interpretation to ‘confirm’ that their previous decisions were reasonable ones. Confirmation bias can be frequently seen in a medical scenario when the therapeutic effect of different treatments is not clear-cut. Some patients may believe in the therapy they used to take and ‘confirm’ its effect by selectively looking for supporting evidence and selectively ignoring the counter-evidence. Simply speaking, it is not just their decisions being biased, but also the way of information processing being distorted. Confirmation bias is also critical to dental practice.

It is not unusual to see some patients ‘come up with their own answers for their problems.‘ For example, patients may believe that their toothache is merely dentine hypersensitivity because they have experienced the same thing. They would selectively report their experience to support the idea that ‘it’s nothing but hypersensitivity’ and ignore the possibility of proximal caries, which is also sensitive to cold stimuli. As dentists, we should avoid the misdiagnosis between hypersensitivity and caries. We should also be aware of the cognitive bias by which patients develop a wrong conclusion.

Another interesting case of cognitive bias is the sunk-cost effect, which means our decisions to carry on action can be influenced by the heavy ‘cost’ or investment we have already done for this action. For example, if people have already invested much money in running a new business, they would keep on running it, even though much more proofs predict the failure of the business. Logically, if all the evidence is against our current action, we should stop it at once. However, by the sunk-cost effect, we refuse to make such a cut. In a clinical scenario, this can be found when patients stick to a therapy that is obviously futile, simply because they have already paid much effort on that therapy.

The ignorance of the base rate is also a common bias found in patients.

This can be best described by Bayes’ theorem: people tend to equate the conditional probabilities from the two sides. For example, the probability when there is toothache, there is pulpal infection is taken the same as the probability when there is pulpal infection, there is toothache. The two probabilities are rarely equal to each other because according to Bayes’ theorem, we also need to consider the base rate to have toothache and pulpal infection. In fact, the rate of toothache is much higher, which implies that many conditions of toothache are irrelevant with pulpal infection.

Now, I wonder if you feel a little bit ‘frustrated’ when learning these biases of the human mind.

But I need to clarify something here: from the point of evolution, there could be some ‘advantages’ for people to have such an inaccurate or even distorted way of information processing. Human beings make a decision by different heuristics, a simplified cognitive ‘short-cut’, rather than gathering all information and making a sophisticated calculation, as a computer will do. According to Tversky and Kahneman, such a shortcut of thinking can be influenced by representativeness heuristic, which relates to the typical or iconic image of things. For example, before delivering oral hygiene instruction, dental hygienists may want to tell a patient with severe periodontitis to quit smoking. The decision is formed because periodontal diseases are much related to the image of a heavy smoker.

Of course, when seeing the patient, the hygienists will modify their plan. Still, the heuristic provides a simplified and time-saving way to formulate a solution. Another heuristic commonly adopted by people is availability heuristic, which means our judgment is shaped by the most available information, i.e., the first thing coming to our mind. For example, when it comes to the case of toothache, one may quickly relate it to dental caries or periodontitis because most people have suffered from these diseases. In addition, such a painful experience can be revived vividly. Therefore, it is not surprising that when there is toothache, patients may quickly come to the conclusion ‘here is another tooth decay’.

Again, this is a quick way for patients to decide to see a dentist. However, it will be the dentist’s job to find something more than the patient’s first impression. For example, pain may be derived from crack tooth, which is less common to patients’ experience.

Wow, I have been aware that some of you would start to argue: Dr Lin, for all these ‘bias’ and ‘heuristics’, you are saying people make stupid decisions? It sounds like people make a decision without a second thought. That’s terrible! Well, that is not stupid at all! To me, that’s even ‘clever’ that we make decisions under the influence of bias and heuristics. It’s all about the context when we make a decision. In many contexts of decision-making, what we need to do is to make a quick response to reduce harm, rather than a thoughtful and perfect decision. These bias and heuristics, and emotion, as we will talk about later, represents a more intuitive and quick way to form a strategy for survival.

My point is that dental professionals should be aware of these biases and heuristics, especially when patients decisions are heavily influenced by them. However, that does not mean the engagement with these biases or heuristics to be ‘irrational’ or ‘not clever’.