On January 20, 2022, CNN reported that a well-known Czech folk singer, who also happened to be a vocal anti-vaxxer, had died of COVID-19 after intentionally exposing herself to the virus so that she could be “done with COVID.” She was confident that COVID-19 posed no serious threat to her health. Hanna Horka’s tragic death is attributable in part to misinformation and perhaps political inclination. But it is quite likely that another contributing factor was the well-known optimism bias that 80% of us suffer.

The optimism bias (also known as the “overoptimism bias”) is, according to psychologist Tali Sharot, “the inclination to overestimate the likelihood of encountering positive events in the future and to underestimate the likelihood of experiencing negative events.” This bias has a neurophysiological basis and is powerful, in part, because people tend not to be consciously aware of it.

Because of the optimism bias, most of us irrationally expect our lives to go better than a rational person would forecast. We predict that we’ll make lots of money and have productive careers, our children will be very talented, and the car wrecks, divorces, layoffs, cancers, and dementia that happen to other people will not happen to us.

Studies show that the optimism bias contributes to the tendency of construction projects to be much more expensive and take longer to complete than originally estimated, of students to not worry about cyberthreats because they think they are much less vulnerable to them than their peers, of taxi drivers to overestimate their ability to drive safely while fatigued, and of bankers to overprice IPOs.

Nobel Prize winner Daniel Kahneman has said: “Most of us view the world as more benign than it really is, our own attributes as more favorable than they truly are, and the goals we adopt as more achievable than they are likely to be. We also tend to exaggerate our ability to forecast the future, which fosters overconfidence. In terms of its consequences for decisions, the optimistic bias may well be the most significant cognitive bias.”

As it happens, unrealistic optimism has many benefits. People with the bias tend to be happier in the moment and more eager to take on the challenges of the future. Irrational optimism helps the rest of us avoid the depression that can plague those who are better calibrated regarding the threats to our happiness that we will face in the future. The optimism bias reduces our stress and anxiety.

But the optimism bias can have adverse effects as well. As Kahneman notes, it can feed our overconfidence bias. We are likely to think of ourselves not only as better drivers and planners than we truly are, we may also overestimate our helpfulness, kindness, honesty and other moral traits. We may just assume that we are “good folks,” and therefore not work thoughtfully and diligently to actually be good folks.

Worse, the optimism bias can exert adverse individual health effects. One study found smokers more than twice as likely as nonsmokers to doubt that they would die from smoking, even if they had smoked for many years. As Dr. Sharot notes, “[u] nderestimating risk may reduce precautionary behavior such as safe sex, attending medical screenings or buying insurance. It could potentially promote harmful behaviours such as smoking, overspending, and unhealthy eating due to the optimistic assumptions that unwanted future outcomes (such as lung cancer, bankruptcy and obesity) are unlikely to materialize…”

From nearly the beginning of the COVID-19 pandemic, psychologists have worried that the optimism bias would lead to deaths such as Hanna Horkas’, because overly optimistic individuals will be convinced that they will not be infected with COVID, or that if they are infected their case will be especially mild, or if it is not mild, Ivermectin, or Hydroxychloroquine, or drinking their own urine will cure them.

Numerous studies from around the world have found that, indeed, the optimism bias has adversely affected many people’s health choices. This is not just theory; it is fact. Hanna Horkas has had a lot of company.

Worse still, these irrational optimists who don’t mask, vax, and/or follow other public health protocols, ultimately endanger others as well as themselves. As Dr. Pascual-Leone and colleagues editorialized in the Annals of Neurology:

Optimism bias is a pervasive human trait related to prefrontal activity and cognitive control. An excessive feeling of personal safety harbors the serious threat of disregarding public health recommendations and failing to adopt personal hygiene practices and precautions that may be uncomfortable and cumbersome, but are critical to protect us all.

Not to make you, dear reader, feel even worse, but, unfortunately, the optimism bias not only inhibits messages regarding the dangers of COVID from getting through to people like Hanna Horkas, it also may prevent many of the rest of us from truly appreciating the danger posed by climate change and acting accordingly. Donald Trump does not believe in climate change. Many of the rest of us do but may, because of the optimism bias, not fully realize how bad things are likely to get and how adversely climate change will affect us individually, leading us not to act as we should to make our own contributions to minimizing the danger.  In a recent study, psychologist Geoffrey Beattie found that:

…optimists have a stronger optimism bias when it comes to estimating the probability of climate change affecting them personally. Non-optimists were twice as likely to think that they would personally be affected by climate change than optimists in the top third…. Optimism can be a very positive thing, but perhaps it has its limits; over-optimism could potentially be very damaging…Sometimes we might need some constructive realism instead. This might be especially true when it comes to climate change. [Beattie]

Don’t know about you, but we’re not feeling as optimistic as we were before we penned this blog post.



Jeffrey Arnett, “Optimistic Bias in Adolescent and Adult Smokers,” Addictive Behavior, 25(4): 625-32 (2000).

Geoffrey Beattie, “Optimism Bias and Climate Change,” British Academy Review 12-15 (Summer 2018).

Aaron Chadee et al., “The Influence of Optimism Bias on Time and Cost on Construction Projects,” Emerging Science Journal, 5(4): 429-433 (20021).

Haoran Chu & Sixiao Liu, “Integrating Health Behaviors Theories to Predict American’s Intention to Receive a COVID-19 Vaccine,” Patient Education and Counseling 104: 1878-1886 (2021).

James R. Dalziel & R.F. Soames Job, “Motor Vehicle Accidents, Fatigue and Optimism Bias in Taxi Drivers,” Accident Analysis and Prevention, 29(4): 489-4094 (1997).

Mihai Dricu et al., “The Neurophysiological Basis of Optimism Bias,” in Cognitive Biases in Health and Psychological Disorders at 41-70 (Tatjana Aue & Hadas Okon-Simger, eds., 2020).

Elena Druica et al., “Optimism Bias During the COVID-19 Pandemic: Empirical Evidence from Romania and Italy,” Games 11: 39 (2020).

Iro Fragkaki et al., “Human Responses to Covid-19: The Role of Optimism Bias, Perceived Severity, and Anxiety,” Personality and Individual Differences 176: 110781 (2021).

Radina Gigova, “Czech Anti-Coronavirus Vaccine Folk Singer Dies after Deliberately Getting Infected with Covid-19, Son Says,” CNN, Jan. 20, 2022, at https://www.cnn.com/2022/01/20/europe/czech-singer-death-deliberate-covid-infection-intl/index.html.

Daniel Kahneman, “Bias, Blindness and How We Truly Think (Part 1). Bloomberg View, October 24, 2011, at https://www.bloomberg.com/opinion/articles/2011-10-24/bias-blindness-and-how-we-truly-think-part-1-daniel-kahneman.

Benjamin Kuper-Smith et al., “Risk Perception and Optimism During the Early Stages of the COVID-19 Pandemic,” Royal Society Open Science, at https://doi.org/10.1098/rsos.210904 (2020).

Stefano Palari & Silvio Vismara, “Over-optimism When Pricing IPOs,” Managerial Finance 33(6): 352-367 (2007).

Alvaro Pascual-Leone et al., “Beware of Optimism Bias in the Context of the COVID-19 Pandemic,” Annals of Neurology 89(3): 423-425 (2021).

Tali Sharot, The Optimism Bias: A Tour of the Irrationally Positive Brain (2011).

Tali Sharot, “The Optimism Bias,” Current Biology 21(23): R941-R945 (2011).

Neil Weinstein, “Unrealistic Optimism About Future Life Events,” Journal of Personality and Social Psychology 39(5): 806-820 (1980).

Neil Weinstein & William Klein, “Resistance of Personal Risk Perceptions to Debiasing Interventions,” Health Psychology 14(2): 132 (1995).

Toby Wise et al., “Changes in Risk Perception and Self-Reported Protective Behavior During the First Week of the COVID-19 Pandemic in the United States, Royal Society Open Science 7(9): 200742 (2020).