Cognitive Biases

A cognitive bias is a systematic pattern of deviation from rational judgment. Unlike random mistakes, biases are predictable: the same type of person, facing the same type of situation, tends to err in the same direction. This predictability is what makes the study of cognitive biases so valuable…

The human brain is not a general-purpose reasoning machine optimised for accuracy. It is an organ shaped by millions of years of evolution in an environment radically different from the one we now inhabit. Understanding this is essential to understanding why cognitive biases exist and why they are…

Over the past fifty years, researchers have catalogued hundreds of distinct cognitive biases. The sheer number can be overwhelming — a 2016 visual codex by writer Buster Benson and designer John Manoogian III organised approximately 188 named biases into a single diagram. Rather than memorising a…

Confirmation bias is the tendency to search for, interpret, favour, and recall information in a way that confirms or supports one's prior beliefs and hypotheses. It is arguably the most pervasive and well-studied cognitive bias, with a research history stretching back to the 1960s.

When people estimate the probability or frequency of an event, they tend to rely on how easily examples come to mind. If instances of something are easy to recall — vivid, recent, emotionally charged — we judge that thing to be common or likely. If examples are hard to recall, we judge it to be…

When we assess the probability that something belongs to a category, we often judge it by how much it resembles our mental prototype of that category — rather than by statistical base rates. This is the representativeness heuristic, another of the foundational heuristics identified by Tversky and…

Hindsight bias is the tendency, after learning the outcome of an event, to believe that we had predicted or known that outcome before it occurred. Once we know how things turned out, the outcome seems obvious — even inevitable. We reconstruct our memories of our prior beliefs to be more consistent…

Humans are storytelling animals. We do not experience the world as a stream of disconnected data points — we experience it as a sequence of events with causes, meaning, and direction. This is a profound cognitive strength: narrative enables complex knowledge to be stored, communicated, and passed…

Rational decision theory assumes that how a choice is presented should not affect the decision made — what matters is the substance of the options, not their packaging. Framing effects demonstrate that this assumption is wrong. The way information is presented systematically changes the choices…

In 1999, psychologists David Dunning and Justin Kruger at Cornell University published a paper titled "Unskilled and Unaware of It: How Difficulties in Recognizing One's Own Incompetence Lead to Inflated Self-Assessments." The paper described a paradox: people with the least competence in a domain…

When we observe someone else's behaviour, we tend to attribute it to their character, personality, or intentions. When we observe our own behaviour, we tend to attribute it to situational factors — the circumstances we found ourselves in. This asymmetry, known as the actor-observer asymmetry, is…

A consistent finding across social psychology and finance is that people favour people, companies, and assets that feel familiar or are associated with their in-group. This preference cannot be fully explained by genuine differences in quality or risk — it operates even when the familiar option is…

You have now read about confirmation bias, availability bias, the Dunning-Kruger effect, framing effects, and attribution errors. There is one further bias that directly undermines the value of all that knowledge: the bias blind spot — the tendency to see cognitive biases operating in others while…

The natural assumption is that knowing about cognitive biases should make us less susceptible to them. The research suggests this is largely wrong. A comprehensive 1982 review by Baruch Fischhoff — the same researcher who documented hindsight bias — found that most direct debiasing attempts fail…

Understanding cognitive biases is valuable. But as the previous leaf established, knowledge alone rarely changes behaviour. The final step is integrating what you have learned into ongoing personal practices — building a mental and behavioural infrastructure that makes better decisions more likely…