One of the greatest fears of any healthcare worker is making a mistake that harms a patient. Unfortunately, whether it’s a delayed diagnosis, an incorrect prescription, not noting an allergy, a mislabeled lab sample, or something else, medical errors are far more common than we’d like them to be. While most errors are preventable, it’s also important to recognize that it’s impossible to eliminate all possibilities of error. “To err is human,” and we are all human. The best way to prevent medical errors is to create systems with enough checks and balances so that it’s harder to make one, but a system can’t be perfect since humans create them.

That said, awareness is one-way individuals can reduce their likelihood of making mistakes. That awareness starts with understanding why humans err and what it is about us that successful anti-error systems are trying to overcome. In short: cognitive bias. But let’s unpack what that means because understanding how your brain operates may help you become more aware of the specific ways you may be susceptible to error.

Humans Rely on Heuristics

Every day, people encounter millions of stimuli that play a role in the thousands of decisions they must make. It would be impossible for the brain to manage making all these decisions consciously, so human brains have developed to rely on heuristics. These cognitive shortcuts let people skip the process of receiving, interpreting, analyzing, assessing, and acting on every stimulus they’re exposed to. For example, when humans lived as hunters and gatherers, they needed to be able to tune out the usual animal sounds and sightings that were always present in the forest so that they had enough attention available to perceive both dangers (such as a venomous snake in their path) and their prey. Hyperstimulation in a new environment would put them at risk of missing either of these.

Heuristics continue to be important today in everyday activities like driving. Drivers cannot pay attention to every sign, animal, person, car, and other visual stimuli on and around the road and still engage in the necessary actions to drive. Experience over time allows drivers to develop selective attention so that they can tune out unimportant signs (every single shop sign they might pass or every street sign for streets they don’t need to turn onto), unimportant safety hazards (a squirrel in a tree beside the road as opposed to a squirrel standing at the curb ready to run into the street), and other distractions.

That selective attention allows them to focus on the input they need to make safe driving decisions. Heuristics also explain how you might walk from one end of the hospital to another without actually remembering any part of the walk along the way—because it’s a route you take so frequently that your subconscious and your muscle memory took over, and the walk was automatic.

When Heuristics Become Biases

While heuristics are essential to functioning in the world, they also lead to forming various cognitive biases that can interfere when people take in and interpret information. A cognitive bias isn’t a feeling of prejudice or discrimination against another person or group. In this case, bias refers to the brain’s preference for a particular thought process, belief, action, or decision that occurs without conscious thought.

One of the easiest—and potentially harmful—examples of cognitive bias at work is alarm fatigue. Researchers have explored what contributes to alarm fatigue and ruled out cognitive overload—when you’re simply dealing with too many things at once—and desensitization, when you’re exposed to the alarm so much that you no longer pay attention to it. More likely, alarm fatigue occurs because of selective attention or attention bias: your brain starts to prioritize the processing of one stimulus or activity over another. Of course, that could be due to familiarity or desensitization that wasn’t picked up in the aforementioned study, but there are other possible ways attention bias develops as well. Since alarm fatigue can be a serious problem, researchers have even explored whether it’s possible to overcome it using other heuristics!

Types of Cognitive Biases

More than 100 cognitive biases have been identified, with several overlapping or resembling one another. It’s not important to know every type of cognitive bias out there, but it does help to familiarize yourself with some examples and the ways they can occur in healthcare. One of the most common and pernicious biases is confirmation bias.

Confirmation bias involves unconsciously preferring information that confirms what you already believe. For example, people who seek out information about vaccines online will find a lot of information of varying accuracy. Still, those concerned about vaccines will often use search terms more likely to pull up articles questioning vaccines’ safety. In addition, they are more likely to read and pay attention to anti-vaccine misinformation. The omnipresence of personalized algorithms in search engines worsens this problem because search engines “learn” what a person is more likely to want to see and provide those sites before others.

In healthcare, confirmation bias often hampers accurate diagnosis. Suppose a clinician suspects a patient has a particular diagnosis. In that case, they might focus on the signs and symptoms that confirm that diagnosis while inadvertently neglecting other signs and symptoms that would rule it out or expand the differential diagnosis. One way to reduce your likelihood of falling into this thinking trap is to stop and check yourself: are you leading yourself in a particular direction before you have all the information you need? Could you prove your suspicion wrong if you need to? Unfortunately, many situations in healthcare don’t allow the time and space to do that kind of second thinking, but when it’s possible, it’s worth practicing. In future articles, we’ll explore other types of cognitive bias, how they manifest in healthcare settings, and ways to offset their influence.