top of page
Perfil blog alunos.png

BBI of Chicago
June 2021

Pet Fallacies: How Knowledge About Argumentative Fallacies Can Help Us in Decision Making


By: Jean Lucas Pires.

Cognitive biases are systematic cerebral interferences and tendencies, caused by heuristic processing, that influence the way the brain receives, stores and connects new information. These processes can distort our perception of reality and lead us to make wrong decisions and even be the cause of financial losses when deciding what to buy and how to invest. 

One way of dealing with these biases is getting to know them so that it is possible to identify and avoid them. However, just knowing them might not be enough to overcome them, because our brain can generate well-elaborated argumentative fallacies that convince and misguide us, they are caused by biases such as the cognitive dissonance and regret aversion, for instance, in a way that our feelings, intuitions, beliefs that are disconnected from reality and wrong decisions always look like good and assertive choices.

Decisions based on overconfidence, anchorage, representativity, and other cognitive biases are examples of fallacies that we create to base unfounded intuitions. Those are our “pet fallacies”.

We can also adopt fallacies from others and use them as excuses of our own. Salesmen that use authority or attachment speech, scarcity rhetoric, and other influence triggers with no real base, in reality, are examples of such fallacies.

Some argumentative fallacies are easily identifiable, for instance, when we feel like a product is cheap based on a sizeable percentual discount, when, in reality, even with that discount applied the product is still more expensive than its market price. In the previous example, it is relatively easy to notice the mistake. In other situations, however, it can be harder; for example, when we try to support the idea of investing in financial assets based on the qualifications of the one who manages that fund or the success of the broker. Even if the arguments are true, the conclusion might not necessarily be so.

Therefore, knowing and understanding the systematics of argumentative fallacies, especially the more complex ones, can be very useful in the decision-making process, in a way that makes it easier to critically evaluate our options and deal with our fallacious creations or unfounded ideas from others.




Dobelli, R. (2014). A Arte de Pensar Claramente. Rio de Janeiro - RJ: Editora Objetiva.


Kahneman, D. (2011). Rápido e Devagar - Duas Formas de Pensar. Rio de Janeiro - RJ: Editora Objetiva.


Lobão, J. (2012). Finanças Comportamentais. Lisboa: Conjuntura Actual.


Sbicca, A. (15 de Abril de 2014). Heurísticas no estudo das decisões econômicas: contribuições de Herbert Simon, Daniel Kahneman e Amos Tversky. Source:


Schopenhauer, A. (2014). 38 Estratégias para Vencer Qualquer Debate - A Arte de Ter Razão .

Barueri - SP: Faro Editorial.

Look out other articles of our students

bottom of page