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Making Good Decisions – Cognitive Biases and Logical Fallacies

By Tony Koutsoumbos, Fundraising Specialist for the I Am GroupThinking,_Fast_and_Slow

Last night I delivered a talk on the impact of cognitive biases on decision making and the logical fallacies that turn faulty assumptions into false conclusions. Below is a summary of the key points and – more importantly – a list of the most common biases and fallacies.

In a nutshell:

The ability to think quickly is a prized asset in a demanding job, yet it can lead to bad decisions by embedding flawed assumptions in our system of thinking. However, by scrutinising the link between these assumptions and the conclusions they lead us to, we can prevent this from happening.

Fast Thinking v Slow Thinking:

In his 2011 book, Thinking Fast and Slow, Nobel Prize winning psychologist Daniel Kahneman argues that humans have two different systems of thinking: the intuitive system and the logical system. The intuitive system is fast and flexible, but crude and inaccurate. The logical system is slow and cumbersome, but precise and correct. He believes that we make bad decisions because we are over-reliant on intuitive thinking.

Cognitive biases:

Simply thinking slower is not the solution because a lifetime of over-reliance on fast thinking has embedded flawed assumptions in our minds that influence slow thinking too. These are known as cognitive – or unconscious – biases. Acting on these biases doesn’t mean your decision will automatically be wrong – it just means it won’t be rational and so the chances of it turning out right will be more down to luck than logic.

Logical fallacies:

Faulty assumptions lead to cognitive biases because they are not subjected to the same level of scrutiny as other claims. The result is a false conclusion that has no basis in fact. The riddle below is an example of this.

A doctor and a boy go fishing. The boy is the doctor’s son, but the doctor is not his father. How is this possible?

The answer is of course because she’s his mother. Yet, the immediate assumption many of rush to without questioning – even the most liberal minded among us – is that the doctor must be a man. The wrong conclusion is therefore reached because the logical link between the assumption we are making and the conclusion we draw from it is broken. This is called a logical fallacy and the failure to root it out is what leads to cognitive bias.

How to make better decisions:

3 steps to tackle cognitive bias when a big decision needs to made

  • Appoint two or more trusted colleagues to be advocates for all of the options you need to choose between and task them with delivering the arguments you have already prepared in favour and against each one.
  • Invite them to make the case for their assigned option and to critique one another.
  • Judge their cases, using a checklist of logical fallacies, to identify faulty assumptions and analyse the remaining arguments using your own list of priorities as a comparative framework.


Turning your office into a debate chamber is not the model for optimum decision making, but a stepping stone for you to learn how to detect and eliminate cognitive bias yourself. It will allow you to isolate the faulty assumptions that have gone unchallenged throughout a life of fast thinking and prevent them from inhibiting your ability to make rational decisions.

Links and resources

1 Response

  1. iam

    Glad you found this useful! Why not check out some of our other blog posts? We are currently working on a series about how to make our ideas stick 🙂

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