Your brain – the enemy within

Humberto Aguilera, Ph.D.

Psychology Faculty

Every day is a challenge – a challenge in which we need to resolve hundreds of issues. Some of these issues seem trivial while others seem important, and our brains resolve hundreds of small decisions for us every day.

Julie Svarovská

Student in the Master's in Professional and Business Communication program

Pretty amazing, right? Not so much. For many years, I was convinced that the brain was the most complex organ that you can ever imagine. Throughout my formal education, I heard astounding evidence over and over again, and very rarely an opposing view. But although the brain is an organ that works quite well for surviving, it’s terrible for rational thinking.  In the book “Kluge: The Haphazard Construction of the Human Mind,” Garry Marcus (2009) defines the human brain as a “kluge.” In other words, a cobbled-together solution to a problem that’s both clumsy and inelegant. Marcus’s book reminded me of the cognitive biases that I briefly reviewed in my Social Psychology course over a decade ago. The term “cognitive bias” was coined by Kahneman and Tversky in the 1970s as a systematic error in judgment and decision-making.  The list of cognitive biases grew based on Kahneman and Tversky’s research on decision-making, and there are now more than one hundred known cognitive biases.

Let’s think about the judgments that are involved in daily decision-making. Are they faulty? Probably. For example, think about the photo of the serial killer that you saw yesterday on the local news. You are afraid of leaving home because you don’t want to be murdered, but this is very poor decision-making. First of all, the odds of meeting this serial killer are very low. There very few serial killers in town, so you are highly unlikely to meet this person on the street.  Do the police assume that a serial killer is behind every murder? Of course not – they look for people that the victim could have known. The prime suspect is usually the victim’s partner or ex. Should we worry about the possibility of being killed by our partners? Of course not – the odds of being killed by a partner are also very low compared to the odds of being killed in a car crash. In fact, traveling by plane is much safer than traveling by car, but we remember fatal plane crashes because they get more news coverage than fatal car accidents. These examples of clumsy reasoning are based on Kahneman and Tversky’s availability heuristic. The serial killer and plane crash are easier to recall than the murderous partner and car crash. When we look at things this way, it seems clear that cognitive biases act against rational thinking. Should we worry about how many bad judgments and decisions we make every day? The answer to this question is not so simple.

Cognitive biases may be bad for rational thinking, but they are good for survival. If a lion could be lurking in the bushes, caution could save your life. This is why you worry that the serial killer is on the streets, or that plane crashes are more common than car crashes. Better safe than sorry.

However, this doesn’t mean that the brain is doing a great job. For instance, Gigerenzer (2004) pointed out that the fear of flying after 9/11 led to an increase in driving in the US, and the result was an increase in car accidents. Think about the odds of dying in a terrorist attack compared to the odds of dying in a traffic accident, or for that matter slipping in the shower. Which risk is greater? Do you still believe that your brain is your best friend?



Gigerenzer, G. (2004). Dread risk, September 11, and fatal traffic accidents. Psychological Science, 15 (4),  286-287.

Kahneman, D. (2011). Thinking, fast and slow. New York: Farrar, Straus and Giroux.

Marcus, G. (2008). Kluge: The haphazard construction of the human mind. Boston: Houghton Mifflin

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