What is a Cognitive Bias?
A cognitive bias is a systematic pattern of deviation from rational judgment that affects how people perceive, remember and decide. These mental shortcuts, or heuristics, help the brain process information quickly but can lead to predictable errors in thinking.
A cognitive bias is a consistent, predictable error in thinking caused by the brain's use of mental shortcuts (heuristics) rather than full rational analysis.
- •Automatic and intuitive
- •Emotional and effortless
- •Prone to biases
- •Used for everyday decisions
- •Deliberate and analytical
- •Effortful and logical
- •More accurate but tiring
- •Used for complex problems
Step-by-step worked examples
A juror decides a defendant is guilty within the first five minutes of trial and then only notices evidence that supports that view for the rest of the case. Which bias is this and how does it work?
This is confirmation bias. The juror forms an early hypothesis (guilty). They then selectively attend to evidence that confirms it and downplay contradicting evidence. Result: the initial judgment gets reinforced regardless of the case's true strength.
An investor bought a stock at $100. It drops to $40, but she refuses to sell, saying 'I'll wait until it gets back to $100.' Which bias explains this?
This is the sunk cost fallacy combined with loss aversion. She anchors her decision to the original purchase price ($100), not its actual value. Selling at a loss feels worse than the potential future gain feels good. Result: she holds a losing position longer than a rational analysis would recommend.
A manager estimates a project will take 2 weeks because a similar past project also took 2 weeks — ignoring that this project has three new team members and a tighter budget. Which bias?
This is anchoring bias. The first number encountered (2 weeks) becomes a reference point. New, relevant information (new team, budget) is under-weighted relative to the anchor. Result: the estimate is too optimistic.
Flashcards
Quick quiz
Q1.Which bias makes people overweight the first number they see?
Q2.Believing 'I knew it all along' after an event has occurred is an example of:
Q3.Judging how risky flying is based on recent plane crash news is:
Q4.Cognitive biases exist mainly because:
The full card deck, worked steps and AI-tutor support for “What is a Cognitive Bias?” are in Notek — study by hand before your exam.
Common mistakes
Cognitive biases only affect unintelligent or uneducated people. — Correct: Everyone is subject to cognitive biases regardless of intelligence — they stem from how the brain processes information, not from a lack of knowledge.
Knowing about a bias is enough to eliminate it. — Correct: Awareness helps but rarely removes a bias completely; structured decision processes (checklists, second opinions) work better.
All heuristics are bad. — Correct: Heuristics are usually useful mental shortcuts; they only become biases when they produce systematic errors in specific situations.
Confirmation bias and anchoring bias are the same thing. — Correct: Confirmation bias is about favoring evidence that fits existing beliefs; anchoring bias is about over-relying on the first number or piece of information received.
FAQ
What is a cognitive bias?
A cognitive bias is a systematic error in thinking that occurs when the brain uses mental shortcuts to process information, often leading to irrational judgments or decisions.
What are common examples of cognitive biases?
Common examples include confirmation bias, anchoring bias, availability heuristic, hindsight bias, and the sunk cost fallacy.
How to calculate the impact of a cognitive bias?
Cognitive biases aren't calculated with a formula; they are identified by comparing a decision to what a fully rational, information-complete analysis would predict.
How can I reduce cognitive biases in decision-making?
Use structured checklists, seek disconfirming evidence, get outside perspectives, and slow down for high-stakes decisions to engage more deliberate (System 2) thinking.