principles /
Cognitive Biases

An ever-growing list of the cognitive biases I've encountered.

General Misjudgment


Dunning Kruger Effect - the less you know, less you know you don’t know; thinking you’re better at something than you actually are (illusory expertise)

Curse of Knowledge - once you understand something you assume it’s obvious to everyone


Black & White Thinking - seeing things in absolutes without recognizing details or middle grounds; missing alternative pathways

Narrow Framing - using too narrow of an approach / description of an issue

Anecdotal Reasoning - relying on personal experiences / isolated examples rather than sound arguments

Focusing on the Wrong Variable - not accurately identifying the variables that are most impactful on a decision (80/20 rule)

Faulty premises

Circular Reasoning - beginning with the assumption that what you are trying to prove is already true

Straw Man - addressing a different argument than the one at hand

Generalizing / Causality / Probability

Labeling (Grouping) - tendency to apply general labels and describe oneself / others through such labels

Clustering Illusion - tendency to see patterns in random events

Hasty Generalization - tendency to overgeneralize from small samples (overgeneralizing)

Gambler’s Fallacy - witnessing a small sample of a probability causes you to erroneously predict the chances of the next occurrence

Slippery Slope - erroneously assuming additional outcomes are likely after an initial outcome (however, considering second and third-order outcomes is generally wise)

Plausible / Likely - believing that if something is possible, it’s likely to happen

False Cause - erroneously linking causality between two phenomena when such causality does not exist

Conjunction Fallacy - "Linda has an economic degree and was managing editor of her university's feminist paper. Is Linda more likely to be a lawyer or a lawyer who is involved with women's rights?"


Barnum Effect - tendency to see personal specifics in vague statements (OMG that fortune teller was so right about me!)

Personalizing - believing events relate to you when they actually do not

Information Bias - tendency to seek information when it doesn’t affect action

Tendency to Act - sometimes, action is not immediately needed—there are cases where it's best to suspend decision-making

Mind-Reading - jumping to conclusions about another person’s thoughts, feelings, or intentions by assuming "that's how I would feel"


Groupthink / Bandwagon Effect - thinking that when more people believe something, it's more likely to be true (ad populum)

Stereotyping - expecting individuals from a group to have particular qualities

In-Group Bias - unfairly favoring those who belong to your group

Tendency to Seek Harmony - changing one's stance / beliefs to avoid the discomfort of discord

Relative Satisfaction / Misery - judge oneself in relation to one's peers

Influence of Authority - assuming that judgements from those with authority are more likely to be true

Spotlight Effect - overestimating how much people notice how you look or act

Bystander Effect - presuming someone else will do something in an emergency situation


Outcome Bias - judge a past decision based on the outcome rather than how the decision was made in the moment

Hindsight Bias - using information after the event to reason the decisions made prior to the event

Survivorship Bias - focusing only on surviving examples, thus misjudging a situation


Just World Hypothesis - one's preference for a just world causes one to presume that it exist

Selective Perception - allowing expectations / personal perspectives to influence how one perceives the world

Should / Must Thinking - focusing on how the world “should” be rather than how it actually is

Optimism Bias - overestimating the likelihood of positive outcomes; thinking one is personally less at risk of something bad happening compared to others

Pro-Innovation Bias - over-weighting “innovation” when considering the value of something

Novelty Bias - the desire to believe novel / awe-inspiring things (made this up)

Present Bias - tendency to undervalue the future in relation to the present

Ostrich Effect - ignoring dangerous or negative information by “burying one’s head in the sand”

Negativity Bias - letting negative things disproportionally influence one's thinking (pain hurts!)

Negative Filtering - seeing only the negative in a situation

Pessimism Bias - overestimating the likelihood of negative outcomes

Catastrophizing - overblowing the negative aspects of a situation

Declinism - remember the past as better; expecting the future to be worse than it will be

Initial Impressions

Anchoring - the first thing you hear influences the rest (priming)

Framing Effect - being influenced by context and delivery

Availability Heuristic - overweighting what most easily springs to mind (recency)

Halo Effect / Affect Heuristic - how much you like someone influences your judgements of them (rose-colored glasses)

Ad Hominem - discrediting information by discrediting the source

Endowment Effect - weighting something more than its actual value because you own it

Placebo Effect - if you’re told something will work, it just might

Choice-Supportive Bias - once you've chosen something, you tend to feel positive about it, even if the choice has flaws (this is actually beneficial at times)

Stubbornness & Ego

Confirmation Bias - tendency to seek out information that confirms one's initial belief (and ignore information that disconfirms it)

Belief Bias - similarly, if a conclusion supports your existing belief, you’ll rationalize things to supports it; how heavily you “believe” something to be true influences how you judge it

Sunk Cost Fallacy - the more you've invested in a decision, the less likely you'll change your mind; continuing with something you've invested in despite the rational incentives of not continuing

Backfire Effect - when your core beliefs are challenged, you believe them more strongly

Reactance - doing opposite of what someone is trying to make you do

Fundamental Attribution Error - judge others' actions based on their character, but your own actions based on the situation

Self-Serving Bias - similarly, your failures are due to external factors but you’re personally responsible for your successes


Relying on Intuition / Gut - romanticizing or erroneously giving weight to “gut feelings” (in most situation, gut feelings are accurately tied to the situation at hand)

Emotional Reasoning - misinterpreting emotions as signals of something's value

Tendency to Envy - desiring what others have due to them having it

Sensitivity to Fairness - overvaluing fairness in relation to positive outcomes

Tendency to Believe What Makes You Feel Good - even if it's untrue or non-actionable

Denial / Self-Delusions - not accepting a situation due to how uncomfortable it is

Need for Control - control as a defense mechanism

Intolerance of Uncertainty - uncertainty is uncomfortable; willingness to exchange value for certainty

Influence of Stress - measurable detrimental to thinking ability—avoid making decisions when under duress

Influence of Tiredness - same as above