March 2


Cognitive Bias: 5 Mental Errors That Lead to Bad Decisions

By Sallie Baugh

brain, Classics, cognitive bias, making decisions

Brains are lazy...

AND they are dealing with major Information Overload!  In 2015, research showed that 2.5 Quintillion bytes of data are created every day. Since that number seems to be increasing all the time, we can assume it is far greater now!  As a point of reference, 2.5 Quintillion bytes of data = 100 million Blu-ray discs.

EVERY DAY!!!!!! 

We develop ways of dealing with this data that allow us to choose what to pay attention to and ​what to ignore.  This article will explore some of the shortcuts our brains may take in sifting through the data and how that can result in bad decisions.  You will also discover ways to make better decisions!

The way you think is the result of the way your brain has learned to edit all that information.  The way you think often ends up creating thinking errors. These errors can prevent you from truly understanding the information presented.  

Psychologists call each of these thinking errors a "cognitive bias."

How Do You Create a Cognitive Bias?

Cognitive biases result from:

  • Built-in limitations of perception and memory, and
  • Use of heuristics (rules of thumb).

As mentioned earlier, brains are lazy; they want the best result for the least possible effort.  To achieve this goal, they pay attention to the information that seems to be the most relevant.  Unfortunately, that means we ultimately ignore important, useful information as well.

Let's explore 5 Cognitive Biases that may be negatively impacting your decision-making. Not only are you making some bad decisions, but those who understand these thinking errors may be able to manipulate you! 

(At least they could before you read this article and became more aware!)

Awareness is not the same as thought. It lies beyond thinking, although it makes no use of thinking, honoring it's value and it's power. Awareness is more like a vessel which can hold and contain our thinking, helping us to see and know our thought as thought rather than getting caught up in them as reality.

~Jon Kabat-Zinn

Anchoring Bias

Anchoring bias is the tendency to rely too much on one piece of information, usually the first presented.  

Studies of memory in the lab have shown that people are much more likely to recall the early and the last items from a list of things to remember. Solomon Asch pioneered this research in the forties; it has been replicated many times since.

There are many reasons why we may more accurately recall early-presented information:

  • ​Our attention drifts, making us less diligent in processing later information;
  • The earliest information has been rehearsed longer and consolidated in memory. This makes it more accessible because the pathways to it are more well-worn;
  • We assume we have the most important information at the start, and fail to attend to the rest...

We Make Judgments on the Most Available Information

When people were asked if the tallest Redwood tree is more or less than 1200 feet, the average guess was 844 feet.  When asked if it was more or less than 180 feet, the average guess was 282 feet.  (If you are wondering, the actual height of the tallest known redwood is just over 379 feet.)

Most people are strongly influenced by the first number they hear.

This is used by retailers worldwide - that is why sale prices work so well.  When buyers see an item used to be $250 and now it is only $125 it seems as if they are getting a great deal (regardless of the actual value).

Some restaurants will place a very expensive item on the menu, making the other items seem "reasonable" by comparison.

Our brains don't tend to notice or question these tactics.  Because - this may sound familiar - our brains are lazy.

Attentional Bias

The attentional bias is the tendency of our recurring thoughts to affect our perception.

We have limited capacity for attention, and multitasking is a myth.  We can only do one thing at a time.  When we ‘multitask’, we are switching our attention rapidly between different things.  It isn't possible to truly attend to several things at once.

Some fail to notice remarkable changes in their environment while thinking about something else. "Change blindness" is the name given to this condition.

In one example, researchers asked people in the street for directions. While talking, someone walked between them to divert attention. Many didn't notice a completely different person replaced the original questioner.

Some people failed to notice when the person asking for directions changed gender in those few seconds!

Our Thoughts ​Influence Perception

Our internal thoughts have a very strong ability to influence our judgement and perception. We are very good at not attending to things which don’t interest us, or don’t seem to fit in with our perceptions.  

We also tend to project our interests and thoughts onto situations where they may not be relevant. When we are hyperfocused on something, we tend to see the subject of our focus everywhere.

A good example of attentional bias is something almost everyone will have experienced.  Although we have never been interested in a particular TV show, make of car, celebrity, etc., as soon as we become interested, that show, car, or person suddenly seems to be everywhere.

In reality the frequency of our experience of them has not changed; we simply didn’t notice them before. We weren’t attuned to their presence. Once we tune in, we can’t get away from them.

If Meaningful to Me, It Must be to Everyone - Right?​

We tend to make judgments based on the most noticeable information. If something is meaningful to us, we naturally give it more weight to begin with. In addition, the importance of this particular aspect is constantly reinforced by our perceiving it over and over again.

We (often wrongly) assume, because it seems to be everywhere, that our particular interest is of equally vast importance to everybody else. People are different in the degree to which they present cognitive biases,  Those with strong attentional bias, who tend to see everything in the light of their own special interests, are not only prone to errors of judgement, but terribly boring conversationalists.

When people make the social error of talking endlessly about their children, pets, illnesses, or new car, they are demonstrating attentional bias.  The error in judgement is their belief that everybody else is as interested in their kid, dog, backache, or Prius as they are.

Confirmation Bias

Confirmation bias is the tendency to search for, interpret, focus on, and remember information that confirms one's preconceptions.

This bias has a lot to answer for when it comes to the lack of cognitive flexibility. Confirmation bias makes people stick rigidly to beliefs/practices, even when those beliefs/practices are no longer supported by evidence. Some will continue to be sexist despite endless examples of women making good CEOs and men making good single parents.

Like all biases, confirmation bias comes back to attention. People process on a deeper level that which conforms to an existing belief, and ignore that which doesn’t...

People who have always ‘known’ that women make poor leaders will notice the times when this was true.  They will ignore or brush off anything to the contrary.

Many people will continue to gamble even though they know that the house wins in the end. Remembering the joy of winning (a couple of times) overshadows the pain of losing.

As well as ignoring counterexamples, confirmation bias leads people to give less value to information not matching their beliefs.

What You Believe is What You See...

In the late 1970's, an experiment was conducted at Stanford University. Researchers used a study of the relationship between capital punishment and murder rates in the United States. The information presented was always the same, but the conclusion varied. 

Some participants were told that the conclusions supported capital punishment as a deterrent. Others were told that the evidence did not support the use of capital punishment.

Participants were asked to rate the evidence they had read. In both groups, members interpreted the conclusions in the light of their personal opinions. Those against the death penalty who were told the study supported it devalued the evidence.  They claimed that the methodology was poor and the conclusions unfair.

Those who did support the death penalty promoted the same study as having strong methodology.

When the outcomes were swapped, where conclusions were stated to be against capital punishment, participants against the death penalty were impressed by the methodology.  Those in favor of the death penalty dismissed the study as poorly conducted.

The details of the study always remained the same – the only difference was in the conclusion drawn from the evidence.

To quote Dave Lister from the TV sitcom Red Dwarf, “You see what you want to see, guy.”

Information Bias

Information Bias is the tendency to seek information even when it cannot affect actions.

This form of bias is especially interesting.  It seems to conflict with the brain’s reliance on rules of thumb and simplicity to make decisions. Nonetheless, there is strong evidence that the information bias exists.

Humans are not inherently good at calculating probabilities, or judging the value of information, especially under stress.

We are generally uncomfortable with uncertainty. We rely on limited information because we convince ourselves that it’s all we need to know. If we don’t have the answers, or are afraid of making a mistake, we tend to seek out anything which may help.

Information Bias can be seen in a 1988 study by Baron, Beattie and Hershey, using medical decisions as context. Participants were asked to judge whether a fictional patient should choose to have an expensive scan to diagnose their illness.

The scan would actually be useless in determining which disease the patient had. Even when told that it was useless information, most participants recommended the scan. Why?

Even with Information Overload, People Seek More Information...

The context was high stakes: it involved someone’s health.  With such an important decision, people are naturally afraid of making a mistake. We are also biased to want to do something in stressful situations – to take action. Choosing to do nothing is counter-intuitive, even when it is the rational choice.

People often overuse information in other important situations: looking for a job, buying a house, choosing a career. When we know we have an important decision to make, we become more aware of our own limitations.  

We want to avoid biases, so we seek out all the data we can find. Ironically, because we are poor at determining which information is useful, we often end up confusing ourselves.

The potential value of information can mislead, as can other biases, by the way they are presented or emphasized.

Information gathering may also be the result of procrastination.  We are unwilling to make a commitment, so continue to collect evidence to put off the decision. Sometimes we believe we will find some specific bit of data to end the impasse.

Select the most important factors involved in making a decision, and focus only on those aspects.  This is the best way to deal with the information bias.

Recency Bias

Recency Bias is the tendency to weigh the latest information more heavily than older data.

This bias brings us full circle, as it represents the other side of the Anchoring Bias. This is the tendency to rely too much on more recent information.

Recent information can be more noticeable and available to our recall; we sometimes give it more weight in decision-making as a result.

In the case of early information, there has been more time for data consolidation in long-term memory.  In contrast, more recent information may still be active in working memory and therefore still ‘current’...

From an evolutionary perspective, something happening now is more likely to influence our behavior than a memory.  Our natural survival instinct may guide us to attend more to the most recent information about our environment. In this sense, the recency bias could be the brain’s equivalent of ‘come with me if you want to live.’

The recency bias is what encourages us to form habits, as we tend to go to work the same way every day, visit the same restaurants, shop at the same stores... (There is nothing wrong with that, although it is better for your brain health to mix things up.)

​However, it can cause poor decisions in some cases as other, older and relevant data is ignored.  This can be seen regularly in stock market trading, when more importance is given to recent performance.    

Want some quick ways to help de-bias your brain? Click here to download our "10 Cognitive Bias Modification Strategies for Decision-Making."​

Many other cognitive biases exist that are not covered here.  For a more complete list go to  

While cognitive biases can lead to many mistakes and errors in judgement, stereotyping may be the most damaging end result of over-generalizing.  We can't process information about every person we meet, so we simplify.

We spend the most time with groups we have the most in common with.  This helps us to make finer distinctions when it comes to members of our own race, sex, nationality, or age. For everyone else, the brain doesn't want to waste processing power.

We reduce what we know about unfamiliar groups to a set of simple rules of thumb, and instinctively apply the same ‘knowledge’ to every person we meet from a given group.

We are good at preserving these beliefs even when we meet endless examples to the contrary – which is where cognitive biases come into play.

We tend to believe the first thing we learn about people - whether or not it is true.

​Conclusion & Takeaways

​Our brains are lazy, and massive amounts of data come at them constantly. In order to process the data, shortcuts are developed to help categorize and judge:

  • ​Am I in danger?
  • Is this information useful/relevant to me, or is it stupid/false/irrelevant?
  • Should I buy this item?
  • Do I want to get to know this person or is he/she a loser?
  • Do I have enough information to make a decision or do I need more?

​These are just a few of the questions that our brain is helping us to answer - and sometimes it steers us in a good and useful direction.


Sometimes not so much.


There are dozens of cognitive biases, and only a few are covered here for illustration.

  • Brains are Lazy.
  • Everyone has Cognitive Biases. They are often helpful as we sift through mountains of information.
  • A Cognitive Bias DOES narrow your thinking, and can result in poor decisions.
  • Our cognitive biases can allow us to be influenced to make decisions that are more helpful to others than ourselves (such as buying a car).
  • Awareness of our biases can help us reassess and make better decisions.
  • There are strategies for de-biasing (cognitive bias modification).
  • Expanding your thinking can help minimize negative effects of cognitive biases.

Want some quick ways to help de-bias your brain? Click here to download our "10 Cognitive Bias Modification Strategies for Decision-Making."​

You may also be interested in our Ultra Intelligence program, which is designed to expand your thinking and creativity.​

BrainSpeak would like to thank Dr. Kerry Schofield for her contributions to this article. She is a chartered psychologist, consultant statistician, and researcher in the field of individual differences. Kerry graduated from the University of Oxford in 2003 with a degree in experimental psychology, followed by an MSc in research and statistics, and PhD in experimental psychology.  She is one of the co-founders of Good & Co.

About the author

Sallie has been interested in personal development for as long as she can remember. A former massage therapist, lifestyle counselor, and student of psychology, she has a passion around empowering others to reach their goals and become the best they can be.

{"email":"Email address invalid","url":"Website address invalid","required":"Required field missing"}

Ready for a Better Mind for a Better Life? 

Check out our catalog of transformational personal development programs!