At the time of writing, it is September 21 in New York – the time of year where you would ordinarily expect the heat of summer begin to fade and the first leaves of autumn start to fall. Despite the time of year, yesterday was a hot day, around 29°C (or 84.2°F), quite hot for a September in New York. As a result, I assumed that the weather would be similar the next day, so this morning I got dressed and put on a t-shirt and jeans to head out to work. However, as I left my house, I realised… it was incredibly chilly (around 15°C or 59°F)! I had no time to go home and grab a sweater, otherwise I would miss my train. By the time I got to the train stop, my arms were folded, I had goosebumps all over, and I was angry that I had not checked the weather before I left the house.

I am sure a similar situation has happened to you before, where you anticipated the weather today to be similar to yesterday. This is an example of a cognitive tendency called projection bias: when we use what we experience in the present to make decisions about the future, even if our current state should be irrelevant to our future decisions.

In plain words, when we think about the future, we non-consciously assume that our beliefs and preferences will be the same as they are in the present, and we fail to consider the fact that the future may be very different to our current reality. With my weather example above, projection bias affected my decision-making as I used the temperature of the previous day to make a judgement about today, failing to consider that today the weather is likely to change.

You may be thinking: what does this anecdote about the weather have to do with my emotions, and how can this lead to fatal outcomes? Projection bias is not simply limited to judgements about the weather, but also about our emotions, opinions, and preferences. For instance, the wisdom around ‘Don’t shop when hungry’ is warning you precisely against projection bias: your current emotional state (hunger) influences how you think about the future – you non-consciously project that you will also be hungry in the future, so you over-purchase on your groceries.

From an economic perspective, this is a fascinating topic, as traditional economic models assume that our decisions should be perfectly rational – we should theoretically be able to perfectly predict our future opinions, and preferences, so we make optimal decisions today and will continue to do so in the future. However, as we have just demonstrated, we struggle to do this in reality, where our current state plays a large role in determining our future decisions which are often suboptimal. As a result, behavioural economists have developed mathematical models depicting projection bias which can better predict how our present state affects how we think about the future, which affects our decisions today.[1]

Projection bias, as you can imagine, has many implications for patient healthcare decisions. Many of these examples, importantly, can have potentially lethal consequences, as decisions we make today can impact the consequences we experience in the future, highlighting the importance of understanding this bias. In the below sections, I present some examples of how projection bias influences both patient and physician decisions in the healthcare space, citing academic studies and some of our own experiences at HRW Shift.



Putting off seeing the doctor. Patients who feel an unexpected moderate pain often believe that they do not need to see a doctor immediately. Non-consciously, they are projecting their current state onto their future state, failing to anticipate that their condition is likely to worsen over time and underestimating the amount of pain they will feel in the future. As a result, they put off seeing the doctor until their condition has progressed. We see this quite frequently in our patient research at HRW, where we suggest to our clients to focus on raising patient awareness on the medium and long-term prognosis of conditions, to encourage earlier doctor’s visits.

Life support decisions can depend on pain in the present moment. Decisions to end one’s life are likely to be made based on how much pain they are currently feeling, and may have an overly negative view of their situation. One study found that cancer patients receiving end-of-life care rated their will to live not based on a long-run average of their happiness but based on how miserable they feel in the present moment, where those feeling more pain in the present reported lower wills to live.


Adherence with medication can diminish as patients feel they are recovering. As patients feel their symptoms are alleviating, they may stop their medication, believing that they have recovered. This can lead to a relapse. Patients are using their current recovered state and believe that their future state will be similar, so they decide to stop medication now, failing to consider that they can relapse. This was observed in a study of patients with manic depressive disorder, where half of the patients in the study failed to stick with their drug regimen as they recovered.

Drug addiction

Underestimating how easily you’ll become addicted. Drug addiction has obvious long-run consequences, which makes it an interesting question in terms of standard economics: if drug addiction is irrational (in a standard economics sense), why do people get addicted in the first place? Projection bias provides a potential explanation, as it posits that people first indulge in addictive substances believing they won’t become addicted, but in their unaddicted state they underappreciate how neurologically addictive the drug is and how they require a larger ‘hit’ of a drug to have the same effect. Over time, this can build addiction and a habitual dependence on the drug.

Overestimating your ability to quit. People who are drug addicted often have a desire to quit, but this unrealistic desire often occurs when their cravings are low. In this state, they underappreciate that in the future their cravings will once again be high, which can lead to failed attempts to quit.

Adopting healthy behaviours

Starting a new gym routine. You feel a high level of motivation when starting a new workout routine, and tell yourself eg. ‘I’m going to go to the gym everyday for the next year’, and subsequently purchase an annual gym membership. You fail to consider that our motivation dwindles over time, meaning we will go to the gym less and less, making the annual gym membership a miscalculated decision.

Health insurance purchases

Health insurance sales and pollution. Using data from a large Chinese insurance company, one study found that health insurance contract sales went up by 7.2% on days where there was bad air pollution. People perceive that the bad air quality would persist into the future and were therefore more inclined to purchase health insurance on days where it would be bad. On the flip side, health insurance sales went down by 4% when air pollution was not bad.

It’s clear that projection bias can heavily influence a variety of decisions relating to how we think about healthcare decisions outside of our conscious awareness, but combating it is another issue given how multifaceted the challenge of projection bias is. There is no clear one-size-fits-all solution. Often, we need to consider each problem on a case-by-case basis, understanding how exactly projection bias is impacting decision-making before moving forward with solution that can specifically overcome the barrier. For instance, habit forming strategies such as incentive programs may work for medication adherence, drug addiction, and adopting healthy behaviours; while ‘cooling-off periods’ may be a solution for patients on life support or those who are contemplating to consume an addictive substance. When deciding between multiple potential solutions and thinking about what might work best, it’s vital to test: conduct research to evaluate what are the potential consequences for any given solution.

One step in the right direction is promoting awareness that this bias exists, as greater awareness means that people will be more cognizant of it and take more conscious actions to try and overcome it. Hopefully with your new awareness of projection bias, the first thing you will be more considerate of is to check the weather before choosing what to wear tomorrow.


By Tony Jiang

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