Biases
Cognitive biases are systematic tendencies in how we perceive, remember, and judge—shortcuts and blind spots that helped our ancestors survive but often lead us astray when we estimate quantities, weigh evidence, make decisions, or report what we think. Unlike logical fallacies (flaws in the structure or content of an argument), biases are tendencies in the thinker: we bring them to the situation before anyone has argued with us.
They can be harmful because they distort our view of reality without our noticing: we overconfidence in what we recall, we anchor on the first number we hear, we seek evidence that confirms what we already believe, and we misattribute causes. In judgment, planning, and belief formation, unrecognised bias can undermine both individual choices and collective decisions.
Knowing them is a core part of critical thinking: it makes you more able to question your own intuitions, design processes that correct for bias (e.g. in estimation or hypothesis-testing), and interpret others' claims with appropriate caution. Below is a reference list of cognitive biases grouped by the kind of task they affect; expand a subcategory to see its list, and click a bias name for a full explanation and examples.
Estimation biases
Systematic errors when we judge quantities, frequencies, or magnitudes.
Decision biases
Systematic errors when we choose between options or commit to a course of action.
Opinion reporting biases
Systematic errors in how we state or report what we believe or prefer.
Hypothesis assessment biases
Systematic errors when we evaluate evidence for or against a belief or hypothesis.
Recall biases
Systematic errors in what we remember and how we remember it.
Causal attribution biases
Systematic errors in how we assign cause and effect.