Unconscious Biases: The Systematic Errors In Our Thinking

We have systematic errors in our thinking that affect our decisions and our actions.  These errors are universal and our brains are wired in such a way that they sometimes impact our decisions and actions.  Unconscious biases are some of these systematic errors—ones that have ramifications for diversity, inclusion and corporate advantage

Thinking Fast and Slow

In his book. Thinking Fast and Slow, Daniel Kahneman describes a lifetime of research devoted to how our brains make decisions (Kahneman, 2013).  His framework for how our minds work and when we make mistakes provides the perfect model for understanding unconscious biases. 

Figure 1.  Our Thinking and Our Systematic Errors

Our brain relies on two types of thinking: fast thinking and slow thinking.  Fast thinking (also called implicit cognition, unconscious thought and unconscious inference) is our intuition and our gut reactions.  Slow thinking is deliberate, informed and responsible for most of our decisions and actions. Our slow thinking filters our fast thinking to align it with our intentions and values.

Fast thinking is a necessity because of the mass amount of input we face in any moment.  In fact, thinking quickly is a biological necessity and one that has historically kept us alive.  As the amount of information we face on a daily basis increases, our brains become even more effective categorizing and associating machines.  

Systematic Errors

While generally, our fast thinking is correct, we all have systematic errors or biases. In this sense, systematic means they are predictable and common between people.  Take for example the lines in Figure 2, which one is longer?  

Figure 2. The Muller-Lyer Illusion

You likely identified that the line in the middle was the longest, most people do.  This is a systematic error in our fast thinking that is shared by most of us. Even if you have seen this before and know that the middle line is exactly the same size as the other two lines, you probably still “see” it as longer.  When it comes to the lengths of lines on our computer screens, our errors are innocuous. But systematic errors with respect to other people are unconscious biases that have the potential to cause harm.

Systematic Errors About People

Our brains are association making machines and we cannot stop them from associating new information with the information we already have stored.  When information is not novel, our brain will immediately throw the information into a category This process is called repetition suppression and it perpetuates and reinforces our biases.  Repetition suppression creates a situation where every person of a particular “category” ends up in a single bucket in our brain, without us even being conscious of this process.

Categorization is an inescapable process that helps us make sense of our situations and surroundings and because of the design of our culture it is easy to put people into categories and use social groups as the contextual cue that initiates our inference (Catrina, 2012; Liberman, Woodward and Kinzler, 2017.  One example of how this categorization affects our thinking is the Other Race Effect, where we recognize faces of our own race more easily and because the cognitive load on the brain is lighter we develop a preference for them.  This effect is measurable by three months of age and grows over time (Kelly et.al., 2009).  While categorizing is essential and most of the time benign (putting apples or oranges into categories like good and bad), when it comes to categorizing people by social groups we are reinforcing stereotypes and prejudices.

Even though the social groups to which people belong are available and compelling explanations for who they are, we need to be carful in relying on these categories.  These categories are defined by our social structure and our social structure is not representative of the general population.  This is concerning because these categories shape our systematic errors about people—our unconscious biases.  For example, the groups into which we put people are in large part defined by our media and movies, which is created almost exclusively by white affluent men who may or may not have had any authentic relationships with members of the groups they are defining.  There may be no correlation between them and our values, our intentions and what kind of person we want to be.

Addressing Our Errors

Since our brains operate as efficiently as possible and sometimes we rely on our fast thinking, our errors creep into our decisions.  Hence, it is important we understand our errors in thinking and potentially keep them from affecting our decisions and actions.  

Figure 3.  Change Our Thinking to Mitigate Our Systematic Errors

There are two ways to address our unconscious biases and make our actions and behaviors more inclusive: (1) we can correct our systematic errors and (2) we can practice thinking slow.  Both changes take time and dedication and require altering habits. But since these errors create a disparity between our intentions and our actions, we should engage in these changes if we want to maintain self-determination. 


Catrina, S. (2012). Social Categorization as a Manner of Creating Boundaries, Avoiding and Discriminating against the „Other(s)”. Sphere of Politics / Sfera Politicii20(2), 3–10.  

Felkey, A. J. (2019). Inclusion: Corporate advantage & corporate responsibility. ProHabits.

Felkey, A. J. (2019). Individuals: The key to fostering inclusion. ProHabits. 

Kahneman, D. (2013). Thinking Fast and Slow. New York, NY: Farrar, Straus and Giroux. 

Kelly, D. J., Liu, S., Lee, K., Quinn, P. C., Pascalis, O., Slater, A. M., & Ge, L. (2009). Development of the Other-Race Effect during Infancy: Evidence toward Universality? Journal of Experimental Child Psychology104(1), 105–114. 

Liberman, Z., Woodward, A. L., & Kinzler, K. D. (2017). The origins of social categorization. Trends in Cognitive Sciences21(7), 556–568.