Assumptions vs Facts: Why Most People Confuse Opinions with Truth

What is the psychology of our assumption-making process? Assumptions vs facts. Where do assumptions come from, and should we trust them?

Psychology of Assumption

The process of assumptions is a core feature of human cognition, backed by decades of psychological research, though awareness and training can reduce it.

Assumptions derive from our fast thinking system, which directly affects our interpretations. Interpretations are influenced by who we are, our personalities and experience. This is why a large part of our assumption-making process is a projection. We project out who we are, what we think, and generally how we see the world.

Mental shortcuts (heuristics): System one, thinking (fast, intuitive) dominates daily life. We assume patterns, causation, or intent based on incomplete data. Based from the book (Thinking fast and slow) by Daniel Kahneman.

Cognitive biases: Confirmation bias: We seek/remember evidence supporting what we already “know” and dismiss contradictions.

Illusory truth effect: Repeated assumptions (from the media, social circles, or internal ruminations) feel truer over time.

Dunning-Kruger effect: People with limited knowledge in an area often feel the most confident.

Motivated reasoning: Beliefs tied to identity, tribe, or emotion get treated as self-evident facts.

How common is it?

It’s extremely common. Most people rely on assumptions most of the time. This includes in everyday life, politics, health, relationships, investing. People’s assumptions are often reinforced by others that have made similar assumptions about an event. The consensus often amplifies believed assumptions.  

Exceptions Exist

Scientists, effective critical thinkers, or those trained in Bayesian reasoning, statistics, or philosophy (e.g., distinguishing justified belief from knowledge) do better. But even experts falter outside their narrow domain. “Most people” includes the general population, where these habits are widespread.

Other exceptions may include those with certain personality traits. Such as, being very high in trait openness on the big five personality model. These individuals naturally have minds that are open to different information and ideas. They are more likely to question the assumptions of others and consider different possibilities, including seeking knowledge outside of the social circle, or consensus. These are the none-conformists.

Final Comments

Humans are generally wired for speed, quick judgments, assumptions, and decisions (fast thinking system). Their assumptions are often reinforced by the consensus view. However, the consensus view has never been a good indicator of truth. This is because the majority lacks the knowledge and understanding in many areas, especially complex areas. If you include cognitive biases, ego, and the need to be liked or accepted by your peers. Then it’s unsurprising that most people’s assumptions are wrong.

If the assumptions are never questioned or challenged, people will never know they are wrong. It’s also partly why misinformation spreads, and why wisdom starts with recognizing your own assumptions. The more you notice it in yourself, the less it controls you.