Skip to main content

A good user experience starts with a full understanding and knowledge of the users about a specific software, website, or even a simple application. It is not enough to know who they are. It is necessary to go deeper and get the right knowledge and understanding of their motivations, mentalities, and behaviors.

As UX Designer I have been looking for concepts and answers to understand human behavior, and some of the decisions of our daily life, and without a doubt, the most prominent word in all research is “Brain“. The brain is extremely complex. The most basic function of the brain is to keep the rest of the body alive. Among your brain’s 100 billion neurons, some regulate your breathing, heartbeat, and blood pressure and others control hunger, thirst, and sleep cycle. In addition to this, the brain generates the emotions, perceptions, and thoughts that guide our behavior. Then it directs and executes our actions. Finally, it is responsible for the conscious awareness of the mind itself.

Recently I started reading the book: “Thinking Fast and Slow”, a book on behavioral psychology and decision-making by Daniel Kahneman. An excellent reference on important concepts to understand how the human being makes decisions, which in turn explains why the human being makes errors of judgment.

We have two System Way of thinking – System 1 (Thinking Fast), and System 2 (Thinking Slow).

Explanation of System 1 & 2 – Daniel Kahneman

👉 System 1 operates automatically and quickly with little or no effort and no sense of voluntary control. Kahneman describes System 1 as effortlessly originating impressions and feelings that are the main sources of the explicit beliefs and deliberate choices of System 2.

Some examples of the automatic activities that are attributed to System 1:

  • Answer to 2+2=?;
  • Drive a car on an empty road;
  • Understand simple sentences;
  • Detect hostility in a voice.

👉 System 2 allocates attention to the effortful mental activities that demand it, including complex computations. System 2 needs a complex level of concentration and effort. The operations of System 2 are often associated with the subjective experience of agency, choice, and concentration.


  • Tell someone your phone number;
  • Brace for the started gun in a race;
  • Focus on the voice of a particular person in a crowded and noisy room;
  • Count the occurrences of the letter “a” in this article.

We spend almost all of our daily lives engaged in System 1. Only if we encounter something unexpected, or something that needs conscious effort we engage System 2.

“When System 1 runs into difficulty, it calls on System 2 to support more detailed and specific processing that may solve the problem of the moment. System 2 is mobilized when a question arises for which System 1 does not offer an answer… System 2 is activated when an event is detected that violates the model of the world that System 1 maintains.”

Daniel Kahneman

One of the biggest problems with System 1 is that it seeks to quickly create a coherent, plausible story,  an explanation for what is happening  by relying on associations and memories, pattern-matching, and assumptions. And System 1 will default to that plausible, convenient story  even if that story is based on incorrect information.

The key is to use System 2 to teach your System 1 how to make better decisions and to build intuitive wisdom that’s appropriate to a wide range of contexts.

“What You See Is All There Is” (WYSIATI)  

What You See is All There Is (WYSIATI) is a cognitive bias described by Daniel Kahneman. WYSIATI says that when presented with evidence, especially those that confirm your mental model, you do not question what evidence might be missing.

In daily life, decisions made based on the “What You See is All There Is” phenomenon are acceptable if the conclusions are likely to be correct, the costs of a mistake are acceptable, and if the jump saves time and effort. You don’t question whether to eat every day, for example. As a result of WYSIATI and System 1 thinking, people may make wrong judgments and decisions due to biases and heuristics. There are several potential errors in judgment that people may make when they over-rely on System 1 thinking:

  • Law of small numbers;
  • Assigning cause to random chance;
  • Illusion of understanding;
  • Hindsight bias;
  • Confirmation bias;
  • Overconfidence;
  • Over-optimism.


  • Kahneman, Daniel. Thinking, Fast and Slow. 2011.
  • Carter, Rita. The Human Brain Book, 2019.

Leave a Reply