Cognitive Biases, Thinking Errors & Psychological Effects

The tendency to search for, interpret, and recall information in a way that confirms your pre-existing beliefs, while ignoring contradictory evidence.

The tendency to rely too heavily on the first piece of information encountered (the 'anchor') when making decisions.

The tendency to overestimate the likelihood of events that are easily recalled, often because they are recent, vivid, or emotionally charged.

The tendency to believe, after an event has occurred, that you would have predicted or expected the outcome — the 'I knew it all along' effect.

The tendency to react differently to the same information depending on how it's presented — as a gain or a loss, for example.

The tendency to overestimate your own abilities, knowledge, or the precision of your predictions.

The tendency to judge the strength of an argument based on whether you agree with its conclusion, rather than evaluating the logic itself.

A cognitive bias where people with limited knowledge in a domain overestimate their competence. While the original research focused on low performers' inflated self-assessment, the effect is most reliably observed at the lower end of expertise.

The tendency to continue investing in something because of previously invested resources, even when it's no longer rational to do so.

The preference for the current state of affairs, where changes are perceived as a loss even when they could lead to improvement.

The tendency to overestimate the likelihood of positive events happening to you and underestimate the likelihood of negative events.

Under some conditions, having too many options can lead to decision fatigue, anxiety, and worse decisions or complete avoidance. However, research shows the effect is not universal — it depends on how choices are presented and the decision-maker's preferences.

The tendency to give more weight to negative experiences, information, or emotions than positive ones of equal intensity.

We recognise cognitive biases more readily in other people than in ourselves.

Sometimes, when we are presented with evidence that contradicts a belief we hold, we do not update our thinking — we may even hold the original belief more strongly. However, this is not a universal response: most factual corrections do improve accuracy, and strong backfire effects appear mainly in specific identity-threatening, ideological or highly polarised situations.

The belief that society, institutions, or personal circumstances are in inevitable decline from a better past, even when evidence suggests otherwise.

The phenomenon where a person recalls something that did not happen or remembers it differently from the way it actually happened.

The tendency for post-event information to interfere with and alter the memory of the original event.

The tendency to judge an experience based on how you felt at its most intense point (the peak) and at its end, rather than the average of every moment.

The tendency to best remember the first items (primacy) and last items (recency) in a list, while forgetting those in the middle.

The tendency for the emotions associated with negative memories to fade faster than those associated with positive memories.

The failure to notice significant changes in a visual scene when they occur gradually or during a brief interruption.

The tendency to filter information based on your expectations, allowing expected stimuli through while screening out the unexpected.

The tendency to perceive a relationship between two unrelated things, often because they are unusual or stand out together.

The tendency to let a positive impression in one area influence your overall judgment of a person, brand, or product.

The tendency to let a negative impression in one area unfairly influence your overall judgment of a person or thing — the opposite of the Halo Effect.

Suggestions from other people can influence our beliefs, perceptions and memories.

We remember an idea but forget its source, causing it to feel original.

We are less likely to remember information that we believe is stored digitally and easily searchable, because our brains offload the effort of recall to the device.

During intense stress or arousal, time may appear to slow down or speed up. Similar altered time-perception experiences can also accompany medical or mental-health conditions, and persistent, severe or concerning symptoms require professional evaluation.

The tendency to adopt beliefs or behaviors because many other people do the same, regardless of the underlying evidence.

The tendency to attribute greater accuracy to the opinion of an authority figure, regardless of the content of their statement.

The tendency to favor members of your own group over outsiders, giving them preferential treatment, trust, and positive evaluations.

The tendency to see members of other groups as more similar to each other than members of your own group — 'they're all the same.'

The tendency to apply generalized beliefs about a group to an individual member without considering their unique characteristics.

The tendency to assume that others share your current beliefs, values, feelings, or preferences.

The tendency to overestimate how much other people notice your appearance, behavior, or mistakes.

The tendency to evaluate yourself by comparing to others, often leading to feelings of inadequacy or superiority.

The tendency to overestimate how much other people agree with your beliefs, values, and behaviors.

The tendency to attribute others' behavior to their character while attributing your own behavior to external circumstances.

The tendency to attribute your successes to your own abilities and efforts, while blaming failures on external factors.

The tendency for individuals to be less likely to help someone in distress when other people are present.

The belief that the world is fundamentally fair — that people get what they deserve and deserve what they get.

A group prioritises agreement and harmony over careful evaluation of alternatives.

We believe we see reality objectively and assume that people who disagree are uninformed, irrational or biased.

We often believe persuasive messages influence other people more than they influence us.

We explain blame and responsibility in ways that help us feel safer and less vulnerable.

A repeated claim can become increasingly believable and socially accepted because it is familiar and widely discussed.

We assume that other people's behaviour is driven by selfish motives, even when there is good reason to think they are being genuinely helpful or honest.

Interpersonal effects describe how we think, feel, and behave in social interactions based on our interpretation of the other person's likely thoughts, feelings, and intentions. This is an umbrella topic covering several specific interpersonal mechanisms including the halo effect, projection, assumed reciprocity, and self-fulfilling prophecy — not a single universally defined cognitive bias.

Groups may spend excessive time discussing simple minor issues while giving too little attention to complex important ones.

After doing someone a favour, we may sometimes develop a more favourable attitude toward them.

The tendency to prefer avoiding losses over acquiring equivalent gains. The exact magnitude varies by context, but losses generally exert a stronger pull than comparable gains.

The tendency to overvalue something simply because you own it.

The preference to completely eliminate one small risk rather than making a larger overall reduction in risk.

The tendency to overestimate the likelihood of negative outcomes, seeing the worst-case scenario as the most probable.

The tendency to avoid options where the probability of a favorable outcome is unknown, preferring options with known probabilities even when the unknown option might be better.

The phenomenon where adding a third, less attractive option (the decoy) makes one of the original two options seem more appealing.

We give excessive trust to automated recommendations and may overlook contradictory evidence.

We judge people more harshly when bad outcomes follow from risky choices, even when the underlying decision was equally risky in both cases.

When we feel rushed, we tend to fall back on simpler decision rules and heuristics, which can change how we process information, shift our risk preferences, and reduce decision quality. Time pressure does not always make decisions worse — in some cases it can reduce overthinking — but it reliably changes the way we evaluate options.

Groups and organisations can become locked into patterns of behaviour that no longer serve their goals, because acknowledging the need for change would require admitting past decisions were wrong. This is an organisational decision-making phenomenon rather than a single individual cognitive bias — it emerges from how organisational systems reinforce escalation of commitment, groupthink, siloed decision-making, incentive misalignment and the normalisation of deviance.

The tendency to focus on successful examples while overlooking failures, leading to false conclusions about what causes success.

The tendency to ignore general statistical information (base rates) in favor of specific, individual information.

The belief that past random events affect the probability of future random events — for example, thinking a coin is 'due' for heads after several tails.

The tendency to see patterns in random data, interpreting clusters or streaks as meaningful when they occur by chance.

The tendency to believe you have influence over outcomes that are actually determined by chance.

The difficulty of imagining what it's like not to know something once you already know it, making communication with novices harder.

The tendency to believe that a combination of specific conditions is more probable than a single general one.

The logical fallacy of assuming that because something is possible or probable, it is therefore certain or inevitable.

The tendency to stick with the pre-selected or default option, even when alternatives might be better.

The tendency to place disproportionately high value on things you helped create, regardless of their objective quality.

The tendency to value outcomes more highly when they required significant effort, even if the effort was unnecessary.

The tendency to give stronger weight to immediate rewards over future ones, even when waiting would yield a significantly better outcome.

The tendency to underestimate the time, cost, and risk of future actions while overestimating their benefits.

The tendency to remember uncompleted or interrupted tasks better than completed ones.

The tendency to develop a preference for things simply because you are familiar with them.

The tendency to do the opposite of what someone wants you to do when you feel your freedom is being restricted.

The tendency to prefer smaller, immediate rewards over larger, later ones — with the preference growing stronger as the immediate option gets closer.

The tendency to continue behaviors out of habit rather than active decision-making, even when the original reason for the habit no longer applies.

We accept vague and widely applicable personality descriptions as uniquely accurate for us.

We tend to believe that our best moments are representative of our true ability, and we anchor future expectations to those peaks rather than to our average performance. This relates to the Yerkes–Dodson relationship between arousal and performance: peak output occurs at an optimal level of activation, but the inverted-U curve does not apply universally to every person and every task.

Expectations and the treatment context can sometimes influence how symptoms are experienced. A placebo response does not mean an illness is imaginary — it reflects real changes in symptom perception that are distinct from treating the underlying condition.