Cognitive bias A to Z

Lapses that come from divided attention at the moment of encoding or of acting, not from lost memories.

When a decision passes through many hands and a model, no single person feels they made it.

Acting by default rather than waiting, because visible effort feels safer than doing nothing.

We explain our own behaviour by the situation and the behaviour of others by character.

We read our feeling about a thing as information about its risks and benefits.

Confidence in using AI tools runs ahead of the understanding needed to judge what they produce.

Systematic, repeatable unfairness produced by a system and its data rather than by a mind.

Offered a known gamble and an unknown one, we take the known, even when the unknown may well be the better bet.

The first number we are given pulls every later judgement towards it, even when it is irrelevant.

A single vivid case is treated as evidence of a general effect.

We attribute minds, intentions and feelings to things that have none.

Treating an idea as better because it is new.

Treating something likely, or merely possible, as though it were certain.

Concluding a claim is false because the argument offered for it was bad.

A word never presented is recalled as vividly as the studied words that all point to it.

Our state and our preoccupations decide which cues reach us, and the rest go unseen.

A claim gains weight from the rank of whoever made it, whatever the claim itself is worth.

The machine’s answer wins over our own checks, and we stop looking at the evidence it was meant to summarise.

We judge how likely something is by how easily an instance of it comes to mind.

The claim that correcting a false belief strengthens it, which has largely failed to replicate.

The more people we see doing something, the readier we are to do it too, whatever its merits.

A vague profile that would suit nearly anybody reads to us like a sharp likeness of ourselves.

A vivid detail about one case drowns out the plain figure for how common such cases are.

We judge an argument valid when we agree with its conclusion.

A belief outlives the evidence that created it, even after that evidence is withdrawn.

Helping someone raises our opinion of them, even when we disliked them before.

We recognise bias in other people and not in ourselves, because we judge ourselves from the inside.

Asked what follows logically, people answer from content, word order and familiarity instead.

Discussion time runs inverse to importance: groups debate the trivial and wave the consequential through.

Odd or incongruous material is recalled better than ordinary material, but only under narrow conditions.

Whatever we buy with the last of a budget gets blamed for the pinch, and is enjoyed less for it.

With limited time, knowledge and processing power, we take the first option that is good enough.

Pay for things as a package and we use fewer of them, because no single item carries a price to justify.

A claimed priming effect in which the sound of bye calls up buy and nudges spending upward.

Card and phone payments hurt less than handing over cash, so we spend more.

An outcome feels likelier when it sits in a big group, though the size of the group says nothing about its odds.

A face is rated slightly more attractive when seen in a group than when seen on its own.

Too many options degrade the decision, or prevent it being made at all.

We remember the option we chose as better than it was, and the ones we rejected as worse.

Random data contains streaks and gaps, and we read them as structure.

When what we did clashes with what we believe, we ease the tension by bending the belief.

Having backed a course, and been seen to back it, we defend it harder as the bad results arrive.

A false account given sincerely, with no intention to deceive and usually no sense of doubt.

We search, read and remember evidence in ways that shield a hypothesis from rejection.

We test our favoured hypothesis directly and never run the test that would rule it out.

A conjunction is judged more probable than one of the things it is a conjunction of.

Given new evidence we move our beliefs in the right direction, but by too little.

We recall past attitudes and behaviour as closer to our present ones than they were.

Material is easier to retrieve in the setting where it was learned than in a different one.

Retracted information keeps shaping inferences after the person has accepted the retraction.

A thing looks better or worse depending on what we happened to see immediately before it.

Faces from our own racial group are recognised more accurately than faces from other groups.

An idea comes back as our own because we remember the idea but not where we got it.

Material we cannot recall is often still stored, and fails only because the right cue is missing.

Once we know something we cannot model a mind that does not, so we explain it badly.

Each choice wears judgement down, and later ones drift towards the easy default.

The sense that things are sliding, drawn from a tidied past and a noisy present.

An option nobody would pick can still steer the choice between the two that matter.

We assign blame for a mishap in whatever way leaves us least likely to suffer one.

Each successful handover to an automated system invites the next, and the human checks thin out along the way.

We set our clearest and most detailed goals for the parts of life that matter least.

The same sum of money is easier to spend as small units than as one large one.

We cash in winners early and hold on to losers, waiting to get back to even.

Differences that loom large side by side barely register once we live with the choice.

The skill to do a task is the skill to judge it, so the least able overrate themselves most.

How long an experience lasted barely enters our later judgement of how good or bad it was.

We rate an outcome more highly for having worked hard to get it.

We recall our own contribution more readily than anyone else, and claim a larger share of the result.

The method that worked last time comes to mind first and stops us looking for a better one.

From a calm state we badly misjudge how hunger, fear or craving will steer what we, or others, actually do.

Owning something raises what we demand to give it up above what we would have paid for it.

We assume other people are in it for pay and security, while we are in it for the interest.

The unpleasantness attached to a memory fades faster than the pleasantness attached to one.

We take our own view for the common one and expect more agreement than we will find.

A whole event that never happened can be remembered, with detail and confidence, as if it had.

Whatever we are thinking about seems to matter far more to happiness than it does.

Describe the same facts as a gain or as a loss and people choose differently, though nothing else has changed.

After noticing something for the first time, we see it everywhere and take that for a real increase.

An object’s usual job hides its other uses, so the tool we need sits unseen in front of us.

We read other people’s actions as proof of character and overlook the pressures they were acting under.

We expect chance to even itself out, so after a run of one outcome the other feels overdue.

Material we produce ourselves is remembered better than the same material read.

When a search can find it, we keep the location and let the answer go.

We read a group decision as the preference of every member, and one member as the whole group.

A group ends its discussion further out than its members started, and more confident about it.

A group converges on one view and its members quietly abandon the doubts they came in with.

One good quality spills over, so whoever impresses in one way gets rated well in every other.

Confidence exceeds accuracy on hard question sets and falls short of it on easy ones.

Rules of thumb that make judgement fast and cheap, and sometimes systematically wrong.

Once we know the outcome, we misremember having expected it.

It always takes longer than you expect, even when you allow for it taking longer.

After a run of successes we expect another, though the evidence for real streaks is mixed.

Humorous material is recalled better than neutral material, largely at the expense of the material around it.

A short wait cuts a reward’s value steeply, so smaller-sooner wins until both options are far away.

One named person with a face draws more sympathy and money than thousands counted in a statistic.

Things we assembled ourselves seem worth far more to us than they are to anyone else.

We believe we know others better than they know us, and that our side sees theirs more clearly.

We credit ourselves with steering outcomes that are really down to chance or to other people.

We think we understand how things work in detail, until we try to explain one.

We credit whoever handed us an outcome for a satisfaction we produced ourselves.

Our nerves and intentions feel written on our faces, but other people read far less of them than we assume.

Evidence that hangs together feels predictive, so we trust forecasts that weak data cannot support.

Improvement that did not occur is remembered, because the past self is reconstructed to flatter the present one.

We see two things moving together when, counted properly, they have nothing to do with each other.

Most people place themselves above the median on most desirable traits, which cannot be true of most people.

Each repeat of a claim makes it more believable, whether the claim is accurate or not.

We expect good and bad news to hit harder and linger longer than it does once it arrives.

A reaction-time task whose scores are widely read as a measure of hidden prejudice.

Group-linked associations activate automatically, whether or not the person endorses them.

We favour people who share our label, even when the label was handed out at random.

Using rewards and penalties to steer behaviour, on the assumption that people will do what pays.

Seeking more information even when no possible answer would change what we do.

Each person sensibly defers to those who spoke first, and the group ends up knowing less than its members.

How likely a sample result is gets judged without using how large the sample was.

Assuming the world settles its accounts, so that a person’s misfortune is read as something they earned.

Within spaced study, the wider the gap between repetitions, the longer the material lasts, up to a point.

Having mastered a method, we start finding problems everywhere that seem to call for it.

Judged on its own, the lesser option can beat the option that would beat it in a direct comparison.

Each retelling of a memory trims the minor details and inflates the few that carry the point.

Working with what material means makes it stick far better than handling its surface or repeating it.

A long-disputed claim that the language we speak shapes what we notice and think.

The share of a list we recall falls as the list grows, even as the total recalled rises.

Search enough places and something will cross the line by chance, so a single hit means little on its own.

Losses sting more than equal gains please, by a disputed factor of about two.

A capacity limit, not a bias: immediate memory holds a handful of chunks, and probably nearer four than seven.

Concluding that two things differ because someone knows them under different descriptions.

Retrieving some material actively suppresses related material that was not retrieved.

Money gets sorted into pots by source and purpose, and each pot is spent by its own rules, though a pound is a pound.

Liking grows with repeated contact, even when nothing about the thing has changed but its familiarity.

We decide whether to believe something by sizing up the person who says it.

Information supplied after an event alters what a person remembers seeing.

The last few items in a list are recalled better when heard than when read.

We read money at its face value and forget what it will buy.

Our current mood makes material that matches it easier to recall than material that does not.

Having done something good makes us freer to do something questionable next.

We praise and blame people for outcomes they did not control, which philosophy calls moral luck.

A question containing a wrong but fitting term is answered rather than questioned.

Not knowing what we will win can make us try harder than knowing we will win more.

The adage that anything that can go wrong will go wrong, sustained by selective memory.

Given several options at once, we split evenly between them, so whoever draws the categories sets the shares.

We expect other people to be more self-serving than they actually turn out to be.

Believing we see things as they are, so anyone who disagrees must be misinformed or biased.

Bad things register louder and stay longer than good things of matching size.

Under uncertainty, the probability is not weighted badly — it is not used at all.

We remember little of what happened in the moments just before our own turn to perform.

A company’s good deeds make its products seem better, even on qualities the good deeds cannot touch.

Because disaster has never happened to us, we treat it as something that will not, and react late when it does.

A warm memory of the past loosens our grip on money, making us readier to spend it and give it away.

Ideas, tools and evidence from outside are rejected for being from outside.

What the researcher hopes to find leaks into how participants behave and how their behaviour gets recorded.

A rule for choosing between explanations that fit equally, not a claim that the simple one is true.

Harm done by doing something feels worse to us than the same harm let happen by doing nothing.

We expect life to go better for us than for the people around us, and plan on that basis.

Which way a familiar object faces is remembered wrongly, confidently, after thousands of exposures.

When the news is likely to be bad, we leave it unopened, including news about how we ourselves are doing.

We perceive less variety among members of other groups than among members of our own.

We grade a choice by the result it happened to get, not by the case that could be made for it at the time.

Confidence in our judgements exceeds their accuracy, though how much depends heavily on how the questions were chosen.

A reward for something we already enjoy can replace the enjoyment as the reason for doing it.

A chatbot that talks like a friend gets trusted like one, though it is a product with someone else’s goals.

Seeing a definite thing, most often a face, in material that contains nothing of the kind.

Being shown some of the items you are trying to recall makes the remaining ones harder to retrieve.

We store an experience as its sharpest moment plus its ending, and its length barely registers.

Safety regulation delivers less than promised because people take more risk once protected.

We expect the bad version of events, for ourselves or for the world, more often than the record supports.

Concepts studied as pictures are recalled and recognised better than the same concepts studied as words.

Improvement produced by the expectation of a treatment rather than by the treatment.

Plans built from the inside run late and over budget, because the forecast ignores how similar projects went.

Each person doubts the rule in private and stays quiet, sure that everyone else believes in it.

Pleasant material is processed, judged and recalled more readily than unpleasant material of the same intensity.

Older adults attend to and remember positive material more than negative, relative to younger adults.

After choosing, we upgrade what we bought and downgrade what we turned down.

An evaluation of a person that follows from the category they are assigned to.

Anything we get now counts for extra, simply because it is now, against anything that comes later.

What arrives first gets the firmest hold, and frames how everything after it is read.

What we have just met shapes how we read what comes next, and we never notice the hand-off.

An innovation is assumed to benefit everyone, and non-adoption is treated as a failure to be overcome.

Material that costs more effort to process is sometimes better retained, but only certain kinds of effort.

We assume the tastes and wants we have today will still be ours later, and choose for a future self who does not exist.

An outcome that is certain only if an earlier stage goes well is treated as certain outright.

We treat a category as having a hidden inner nature that explains what its members are like.

A threatened freedom is reasserted, and the blocked option becomes more attractive for being blocked.

Studies with positive results reach print; studies that found nothing stay in the drawer.

A teacher’s expectation can shape the pupil it describes, though the classroom effect is far smaller than its fame suggests.

An offer loses value in our eyes the moment we learn the other side made it.

The latest item in a sequence is the freshest in memory and carries more than its share of the verdict.

We choose so as to avoid kicking ourselves later, rather than for the best expected result.

How much a case looks the part stands in for how likely it actually is.

Organisations reallocate resources far less than their stated strategy implies.

Answers to surveys and interviews drift from the truth in predictable directions, whatever the respondent intends.

Confident of our self-control, we walk into more temptation, and the extra exposure is what defeats us.

Advocating the opposite of what you want, so the other person asserts their freedom by choosing it.

Statements that rhyme are judged more true than the same claims in prose.

People adjust how much risk they take to keep their felt level of risk roughly where it was.

Looking back, an experience seems better than it felt at the time, and the past outshines the present.

We attend to whatever stands out and discount whatever does not, regardless of importance.

We notice and retain what fits our commitments and let discrepant material pass unregistered.

Material judged against ourselves is remembered better than the same material processed for meaning alone.

Wins get filed under our own ability and losses under bad luck, which leaves nothing to learn from.

The reflex rejection of new evidence because it contradicts established practice.

In any list, recall favours the two ends, and the items in the middle are the ones that go missing.

Recalling items in their original order is a separate capacity from recalling the items themselves.

Reading friendliness as sexual interest, a pattern reported mainly in men and now disputed.

We judge ourselves against the people around us, and resent those the comparison places above us.

People report the answer that looks good rather than the answer that is true.

The shared, mostly unwritten rules about what people here do and what they ought to do.

We keep a memory but lose track of its source, and fill the gap with a guess.

Repetitions spread over time are remembered far better than the same repetitions crammed together.

We feel watched and remembered, while most people barely registered the shirt or the stumble.

We prefer things to stay as they are, and treat the default as the safe choice.

A category, once applied to a person, supplies expectations about what has not been observed.

We search where the data is easy to collect rather than where the answer is likely to be.

Naming the parts of a category raises its total judged probability above the whole.

A statement feels accurate because it means something to us, not because it fits.

One irrelevant spoken word at the end of a heard list destroys the recall advantage of its last items.

Ideas offered by someone else are taken up as our own and acted on without a check.

Money, time or effort already gone keeps us investing in a course that no longer pays its way.

We draw lessons from the winners still in view and forget the failures that dropped out of it.

We mistake a selection criterion for an effect of the activity we admire.

People defend the existing social order even when it works against them.

Choosing between two options, we check cues in order of past usefulness and stop at the first that separates them.

We misdate events, most often by pulling them closer to the present than they really were.

Retrieving material from memory improves later retention more than restudying it for the same time.

We think persuasive media affect other people more than they affect us, and we legislate on that belief.

We badly misjudge the time gained by going faster, especially when already going fast.

A word we cannot produce but can partly describe, felt as being just out of reach.

We see our own behaviour as varying with the situation and other people as acting from fixed traits.

Good acts by our group are credited to character and by other groups to circumstance, and bad acts reverse.

We treat whatever counts as one portion as the right amount to take.

An item that differs from a uniform set around it is remembered better than the rest.

A change must be a constant proportion of what is already there before we notice it at all.

A familiar route feels shorter than an unfamiliar one of the same length.

Taking one hazard to zero feels worth more than a bigger cut in overall harm spread across several.

We read a situation as a fixed pie, where any gain to one side must be a loss to the other.