The Complete
Cognitive Bias Codex
The human brain relies on 188 distinct mental shortcuts to survive. Explore the ultimate database of psychological blind spots and learn how they dictate consumer behavior, UI/UX, and marketing.
The 4 Pillars of Psychology
Select a category below to explore the cognitive biases associated with how our brains process information, assign meaning, act under pressure, and store memories.
The Problem: Too Much Information
To handle the massive amount of information in the world, the brain filters out noise and only notices what is primed, changing, bizarre, or confirms existing beliefs.
Bizarre, funny, visually striking, or anthropomorphic things stick out more
Bizarreness effect
We remember the weird over the normal. Marketing: Using surreal, strange ad creatives to stop the scroll.
Humor effect
Funny items are remembered better. Marketing: Witty social media presence (e.g., Wendy's, Duolingo).
Von Restorff effect
The item that stands out is remembered. Marketing: Making the 'Pro' pricing tier a completely different, bright color.
Picture superiority effect
Images are remembered better than words. Marketing: Infographics convert better than text blocks.
Self-relevance effect
Memory is better for things relating to oneself. Marketing: Using 'You' instead of 'We' in copywriting.
Negativity bias
Negative things have a greater psychological impact. Marketing: Fear-based headlines ('Avoid these 5 mistakes') get more clicks.
We notice when something has changed
Anchoring
Relying on the first piece of info. Marketing: Showing a $500 crossed-out price next to the $99 sale price.
Conservatism
Failing to revise beliefs when presented with new evidence. Marketing: The difficulty of convincing legacy buyers to switch to new tech.
Contrast effect
Enhancing/diminishing perception when compared with a recently observed object. Marketing: Decoy pricing strategies.
Distinction bias
Viewing two options as more dissimilar when evaluating them simultaneously. Marketing: Side-by-side competitor comparison tables.
Focusing effect
Placing too much importance on one aspect. Marketing: Highlighting one 'killer feature' to make users ignore missing features.
Framing effect
Drawing conclusions based on presentation. Marketing: '80% Lean' meat sells better than '20% Fat'.
Money illusion
Thinking of money in nominal, not real terms. Marketing: Unnoticed price hikes during inflation.
Weber-Fechner law
The difficulty in noticing small changes. Marketing: Shrinkflation (reducing package size slightly without changing price).
We are drawn to details that confirm our own existing beliefs
Confirmation bias
Favoring info that confirms existing beliefs. Marketing: Loyal Apple users actively seeking out positive iPhone reviews.
Congruence bias
Testing hypotheses exclusively through direct testing. Marketing: Marketers only A/B testing variations they already like.
Post-purchase rationalization
Persuading oneself a purchase was a good idea. Marketing: Post-purchase email flows validating the buyer's choice.
Choice-supportive bias
Remembering one's choices as better than they actually were. Marketing: Creating brand tribalism.
Selective perception
Expectations affecting perception. Marketing: Seeing a brand as 'premium' makes their standard product seem better.
Observer-expectancy effect
A researcher's belief altering the result. Marketing: Biased customer surveys.
Experimenter's bias
Similar to observer-expectancy, skewing data to fit a narrative.
Observer effect
The act of observing alters the outcome. Marketing: Focus groups acting differently than real buyers.
Expectation bias
Relying on expected outcomes. Marketing: Anticipating high sales on Black Friday regardless of actual offer quality.
Ostrich effect
Ignoring negative information. Marketing: Ignoring bad customer reviews instead of fixing the product.
Subjective validation
Perceiving statements as true if they have personal meaning. Marketing: Horoscopes and generic 'personalized' marketing.
Continued influence effect
Believing misinformation even after correction. Marketing: The lingering damage of bad PR.
Semmelweis reflex
Rejecting new evidence that contradicts paradigms. Marketing: Blockbuster rejecting Netflix's model.
We notice flaws in others more easily than we notice flaws in ourselves
Bias blind spot
Recognizing bias in others, but failing to see it in oneself. Marketing: Assuming competitors are manipulating data, but your team is objective.
Naïve cynicism
Expecting more egocentric bias in others than in oneself. Marketing: Assuming a competitor's charity campaign is purely for PR.
Naïve realism
Believing we see reality objectively, and others are irrational. Marketing: 'Why don't customers understand our amazing product?'
The Codex visualization and grouping is based on the phenomenal work by Buster Benson and John Manoogian III.
View High-Res Official Codex Map