“What is the difference between logical fallacies and cognitive biases” is a question you occasionally hear people ask. Even though both fallacies and biases are very different from each other, they are both typically concerned with the same issues – errors in reasoning.

️🧠 In short: Cognitive biases are our built-in patterns of thinking and affect how we interpret and process information from the world around us, and logical fallacies are errors or tricks of thought committed in an argument, and they relate to how we construct arguments and communicate ideas to others.

Now, let’s look at biases, fallacies and the difference between them in more detail.

Logical fallacy

Logical fallacies are flaws in an argument that weakens the argument or makes the conclusion invalid. These flaws, which may be committed deliberately or by accident, include drawing of false conclusions, distortion of an issue, an erroneous line of reasoning, misuse of evidence, or misuse of language.

One of the most common types of logical fallacies is the ad hominem, in which someone attacks the person who is making an argument rather than criticizing the validity of their argument.

🚙 For Example

Person A: “Toyota makes better cars than Volkswagen.”
Person B: “That can’t be true since you are an idiot.”

Person B commits the ad hominem fallacy by using an irrelevant insult as proof that person A’s claim is untrue; calling A an “idiot” doesn’t address their claim and does nothing to disprove it.

Logical Fallacy - definition

Cognitive bias

Cognitive biases are our systematic inclinations towards certain patterns of erroneous thinking (or “irrationality”) when processing and interpreting information in the world around us. They are largely products of evolution to help us survive by simplifying information processing.

As such, biases greatly influence our behavior, opinions, and the decisions we make – and have made in the past. For example, the way you remember an event may be biased and affect your behavior today. Also, how we behave socially is dictated by our own “subjective social reality” that is based on our subjective perception of the information and experiences we get.

Fallacy vs Bias

As mentioned earlier, the important difference between biases and fallacies is that biases affect how you interpret and process information, and fallacies relate to how you construct your arguments and communicate your ideas.

This means that they are closely related to each other; a cognitive bias is often the inclination to commit a logical fallacy in an argument.

Let’s look at a couple of examples of the relation between biases and fallacies.

Appeal to popularity is a logical fallacy that occurs when the popularity of something is offered as evidence for its truthfulness. Its logical form goes:

  • Everybody is doing Y.
  • Therefore, Y is the right thing to do.

♎️ An example of this fallacy would be:

“There must be some truth to astrology since around 25% of adults in America believe in it. That many people can’t be wrong!”

The fallacy of appeal to popularity is mainly caused by the bandwagon effect – a cognitive bias that refers to the tendency to do or believe things according to their popularity. As such, when a fallacy is caused by a built-in pattern of thinking, it can be especially difficult to spot and correct.

👉 Another example:

Let’s say that person X is walking on the street. He sees person Y from country A assaulting another person, seemingly without any good reason. Person X concludes that all people from country A are dangerous, aggressive, and irrational people.

In this example, person X has committed the logical fallacy of overextended outrage, which is a statistical error in reasoning when taking the actions of an individual and concluding that it is a norm within the said group.

This fallacy can be the result of a cognitive bias called group attribution error, which refers to the tendency to believe that the characteristics of an individual group member are reflective of the group as a whole.