๐Ÿง  The Psychology of Design:

100 Cognitive Biases & Principles That Affect Your UX

Every time users interact with your product, they:

  1. ๐Ÿ™ˆ Filter the information
  2. ๐Ÿ”ฎ Seek the meaning of it
  3. โฐ Act within a given time
  4. ๐Ÿ’พ Store bits of the interaction in their memories

So to improve your user experience, you need to understand the biases & heuristics affecting those four decision-cycle steps.

Below is a list of cognitive biases and design principles (with examples and tips) for each category. Letโ€™s dive right in.

PS: Don't have time to read the whole list? Just get the cheat sheet.

๐Ÿ™ˆ Information

Users filter out a lot of the information that they receive, even when it could be important.

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Hick's Law

More options leads to harder decisions

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Hick's Law definition

Hick's Law predicts that the time and the effort it takes to make a decision, increases with the number of options. The more choices, the more time users take to make their decisions.

Hick's Law checklist

  • Find an area where you have a lot of options or a lot of repetitions.
  • Try to either reduce the number of options or find ways to hide items. (Do they all need to be displayed at once? #progressive disclosure)
  • If you can't minimize the options, try to put them in an easily skimmable order and make sure the items are familiar; else, it won't work

๐Ÿ’ผ

Confirmation Bias

People look for evidence that confirms what they think

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Confirmation Bias definition

People tend to search for, interpret, prefer, and recall information in a way that reinforces their personal beliefs or hypotheses.

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Priming

Previous stimuli influence users' decision

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Priming definition

Subtle visual or verbal suggestions help users recall specific information, influencing how they respond. Priming works by activating an association or representation in users short-term memory just before another stimulus or task is introduced.

Priming examples

  1. The friendly-looking airport landscape lets the users dream about their next trip increasing the chances of a positive experience:

  2. Superhuman's onboarding includes a priming on the fact that you'll receive some helpful onboarding emails from their CEO

  3. Anti-Example: Tinder misses a great opportunity to prime new singles during the onboarding:

๐Ÿš›

Cognitive Load

Total amount of mental effort that is required to complete a task

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Cognitive Load definition

Cognitive load is the total amount of mental effort that is required to complete a task. You can think of it as the processing power needed by the user to interact with a product. If the information that needs to be processed exceeds the userโ€™s ability to handle it, the cognitive load is too high.

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Anchoring Bias

Users rely heavily on the first piece of information they see

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Anchoring Bias definition

The initial information that users get affects subsequent judgments. Anchoring often works even when the nature of the anchor doesn't have any relation with the decision at hand. It's useful to increase perceived value.

Anchoring Bias examples

  1. Tinder's pricing table shows the most expensive subscription plan first (the anchor) so that the other plans look inexpensive in comparison:

  2. Brick and mortar shops often display very expensive items in the front with visible price tags so that the item you end up seeking seems cheaper.

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Nudge

Subtle hints can affect users' decisions

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Nudge definition

People tend to make decisions unconsciously. Small cues or context changes can encourage users to make a certain decision without forcing them. This is typically done through priming, default option, salience and perceived variety.

Nudge examples

  1. The default purchase option on some Amazon products is a "subscription". They incentivize this automatic recurring purchase by offering a discount:

  2. While you search for a place to stay, Airbnb nudges you to add a date and number of guests instead of forcing those filter:

๐Ÿฐ

Progressive Disclosure

Users are less overwhelmed if they're exposed to complex features later

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Progressive Disclosure definition

An interface is easier to use when complex features are gradually revealed later. During the onboarding, show only the core features of your product, and as users get familiar, unveil new options. It keeps the interface simple for new users and progressively brings power to advanced users.

Progressive Disclosure examples

  1. One of the best examples of progressive disclosure we've ever seen in an onboarding!

  2. Hopper only shows the bare minimum features when you start searching for a flight:

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Fitt's Law

Large and close elements are easier to interact with

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Attentional Bias

Users' thoughts filter what they pay attention to

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Empathy Gap

People underestimate how much emotions influence user behaviors

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Visual Anchors

Elements used to guide users' eyes

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Von Restorff Effect

People remember more items that stand out

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Visual Hierarchy

The order in which people perceive what they see

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Selective Attention

People filter out things from their environment when in focus

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Survivorship Bias

People neglect things that don't make it past a selection process

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Sensory Adaptation

Users tune out the stuff they get repeatedly exposed to

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Juxtaposition

Elements that are close and similar are perceived as a single unit

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Signifiers

Elements that communicate what they will do

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Contrast

Users' attention is drawn to higher visual weights

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External Trigger

When the information on what to do next is within the prompt itself

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Decoy Effect

Create a new option that's easy to discard

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Centre-Stage Effect

People tend to choose the middle option in a set of items

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Framing

The way information is presented affects how users make decisions

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Law of Proximity

Elements close to each other are usually considered related

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Tesler's Law

If you simplify too much, you'll transfer some complexity to the users

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Spark Effect

Users are more likely to take action when the effort is small

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Feedback Loop

When users take action, feedback communicates what happened

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Expectations Bias

People tend to be influenced by their own expectations

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Aesthetic-Usability Effect

People perceive designs with great aesthetics as easier to use

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๐Ÿ”ฎ Meaning

When users try to give sense to information, they make stories and assumptions to fill the gaps.

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Social Proof

Users adapt their behaviors based on what others do

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Social Proof definition

Social proof is a convenient shortcut that users take to determine how to behave. When they are unsure or when the situation is ambiguous, they are most likely to look and accept the actions of others as correct. The greater the number of people, the more appropriate the action seems.

๐Ÿฆ„

Scarcity

People value things more when they're in limited supply

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Scarcity definition

While scarcity is typically invoked to encourage purchasing behaviors, it can also be used to increase quality by encouraging people to be more judicious with the actions they take. It can come in different forms: Time-limited, Quantity limited, Access-limited. Never fake scarcity if you don't want reactance!

Scarcity examples

  1. Uber Eats is one of the rare apps that uses scarcity in a positive way. They offer users to share the costs delivery with other people if they order quickly enough:

  2. Dark Pattern: Mario Kart offers Tours and special items for a limited time to increase conversion rates:

  3. Dark Pattern: Sleepzy uses unjustified scarcity to pressure new users into buying:

๐Ÿ’ญ

Curiosity Gap

Users have a desire to seek out missing information

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Curiosity Gap definition

The curiosity gap is the space between what users know and what they want or need to know. Gaps cause pain, and to take it away, users need to fill the knowledge gap.

๐Ÿ–ฒ

Mental Model

Users have a preconceived opinion of how things work

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Mental Model definition

A mental model is an explanation of someone's thought process about how something works in the real world. It is a representation of the surrounding world, which might be accurate or not. What users believe they know about your product changes how they use it.

Mental Model examples

  1. Trello does a mental model migration by gradually persuading new users that their Trello "cards", "boards" and "lists" are better alternatives to traditional "todo lists":

๐Ÿ‘จโ€๐Ÿ‘ฉโ€๐Ÿ‘งโ€๐Ÿ‘ฆ

Familiarity Bias

People prefer familiar experiences

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Familiarity Bias definition

Users have an innate desire for things they're already familiar with. And the more we experience something, the more likely we are to like it. So, try to use common patterns when creating new experiences.

Familiarity Bias examples

  1. Superhuman uses familiar keyboard shortcuts to ease the learning curve:

  2. Spotify's podcast play screen is very similar to their song play screen, which eases adoption:

  3. Remember Snapchat's big redesign? Well its users remember very well... And they didn't like it! A strong case of familiarity bias.

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Halo Effect

People judge things (or people) based on their feelings towards one trait

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โ˜Ž๏ธ

Millerโ€™s Law

Users can only keep 5ยฑ2 items in their working memory

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๐Ÿฑ

Unit Bias

One unit of something feels like the optimal amount

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Flow State

Being fully immersed and focused on a task

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๐Ÿ•น

Skeuomorphism

Users adapt more easily to things that look like real-world objects

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Reciprocity

People feel the need to reciprocate when they receive something

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Authority Bias

Users attribute more importance to the opinion of an authority figure

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Pseudo-Set Framing

Tasks that are part of a group are more tempting to complete

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Variable Reward

People enjoy rewards, especially unexpected ones

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Group Attractiveness Effect

Individual items seem more attractive when presented in a group

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๐Ÿšฐ

Curse of Knowledge

Not realizing that people don't have the same level of knowledge

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Aha! moment

When new users first realize the value of your product

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Self-Initiated Triggers

Users are more likely to interact with prompts they setup for themselves

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Survey Bias

Users tend to skew survey answers towards what's socially acceptable

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Cognitive Dissonance

It's painful to hold to opposing ideas in our mind

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Goal Gradient Effect

Motivation increases as users get closer to their goal

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Feedforward

When users know what to expect before they take action

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Occamโ€™s Razor

Simple solutions are often better than the more complex ones

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Noble Edge Effect

Users tend to prefer socially responsible companies

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Hindsight Bias

People overestimate their ability to predict outcomes after the fact

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Law of Similarity

Users perceive a relationship between elements that look similar

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Law of Prรคgnanz

Users interpret ambiguous images in a simpler and more complete form

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Spotlight Effect

People tend to believe they are being noticed more than they really are

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Fresh Start Effect

Users are more likely to take action if there's a feeling of new beginnings

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โฐ Time

Users are busy so they look for shortcuts and jump to conclusions quickly.

๐Ÿง—โ€โ™‚๏ธ

Labor Illusion

People value things more when they see the work behind them

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Labor Illusion definition

Making users wait for something they requested while showing them how it is being prepared creates the appearance of effort. Customers are usually more likely to appreciate the results of that effort. This is also called the "KAYAK Effect" (based on the travel booking site that used that tactic).

Labor Illusion examples

  1. KAYAK (travel booking site) once delayed the time search results page to show that it is "crunching data".

  2. TurboTax showed "validation and analysis" screens when you submit your taxes.

  3. The first time you see your potential matches after you complete your profile, Tinder shows the results so quickly that you might doubt of their quality:

๐Ÿšถโ€โ™‚๏ธ

Default Bias

Users tend not to change an established behavior

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Default Bias definition

Unless the incentive to change is compelling, people are more likely to stick to the default situation presented to them. This is also called the Status quo bias. It can be a powerful actor when trying to change behaviors.

๐Ÿฆ

Investment Loops

When users invest themselves, they're more likely to come back

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Investment Loops definition

People invest time, money, information, or effort into a product in anticipation of future benefits. It makes them more likely to return because of the increase in perceived value. When executed properly, user investments load the next trigger to use your product.

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Loss Aversion

People prefer to avoid losses more than earning equivalent gains

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Loss Aversion definition

We hate losing or letting go of what we have (even if more could be had). Prospect theory says that a loss hurts more than an equal gain feels good. In other words, losing $1,000 will "hurt" more than the joy of gaining $1,000. Loss aversion can also lead to sunk cost fallacy. (Related: Endowment Effect)

Loss Aversion examples

  1. Your fear of losing the Duolingo gems you wager encourages you to maintain the practice streak to which you committed:

  2. Trello's "deferred account creation" relies on the fact that you'll want to confirm your account email AFTER you've created boards, lists and cards because you won't want to lose them:

  3. When you go over the usage limit, Zapier reminds you that you have 30 days to upgrade before you lose your data. It's a powerful incentive to take action now:

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Commitment & Consistency

Users tend to be consistent with their previous actions

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Commitment & Consistency definition

When users are asked to do something, their brain instinctually perceive it as a threat. The smaller the initial ask, the smaller the fight or flight response and the more likely they are to agree to gradually bigger requests. Especially since the brain likes to be consistent with its previous actions. It's part of the reason why multi-step forms can perform up to 271% better than a big single-step form.

Commitment & Consistency examples

  1. Tinder's onboarding splits their signup form in 6 single-question steps to leverage the power of micro-commitment:

  2. Depending of the visitors context, some of our Growth.Design newsletter opt-in prompts use two steps. We AB tested it against a single step (email field) variant and it generated a lift of +11%.

  3. Duolingo email notifications cleverly use the fact that you committed to practice a language to ask you if you "still want to learn it":

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Sunk Cost Effect

Users are reluctant to pull out of something they're invested in.

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Sunk Cost Effect definition

People experience the sunk cost effect when they keep doing something as a result of previously invested resources (time, effort, money, etc). That effect becomes a fallacy if it's pushing them to do things that won't make them happier.

Sunk Cost Effect examples

  1. Duolingo encourages you to bet gems if you think you can keep a practice streak for one week:

  2. Netflix: Have you ever watched a boring movie until the end, simply because you started it? That's sunk cost fallacy in action.

  3. World of Warcraft MMORPG: millions of players keep playing (and paying 15$/month) partly because they've already invested so much time and money in the virtual game.

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Decision Fatigue

Making a lot of decisions lowers users' ability to make rational ones

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Reactance

Users are less likely to adopt a behavior when they feel threatened

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Observer-Expectancy Effect

When researchers' biases influence the participants of an experiment

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Weber's Law

Users adapt better to small incremental changes

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Law of the Instrument

If all you have is a hammer, everything looks like a nail

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Temptation Coupling

Hard tasks are less scary when coupled with something users desire

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Parkinsonโ€™s Law

The time required to complete a task will take as much time as allowed

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Dunning-Kruger Effect

People tend to overestimate their skills when they don't know much

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Affect Heuristic

People's current emotions cloud and influence their judgment

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Hyperbolic Discounting

People tend to prioritize immediate benefits over bigger future gains

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Cashless Effect

People spend more when they can't actually see the money

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Self-serving bias

People take credits for positive events and blame others if negative

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Pareto Principle

Roughly 80% of the effects come from 20% of the causes

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Discoverability

The ease with which users can discover your features

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Backfire Effect

When people's convictions are challenged, their beliefs get stronger

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False Consensus Effect

People overestimate how much other people agree with them

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Barnum-Forer Effect

When you believe that generic personality descriptions apply specifically to you.

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IKEA Effect

When user partially create something, they value it way more

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Planning Fallacy

People tend to underestimate how much time a task will take

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๐Ÿ’พ Memory

Users try to remember what's most important, but their brain prefers some elements over others.

๐Ÿ•

Provide Exit Points

Invite users to leave your app at the right moment

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Provide Exit Points definition

Exit points are meant to respect people's time. They are opportunities to "put down" the product when users feel they have reached something. They are critical to an overall experience when you want to avoid product fatigue and reactance. (Related to: Peak-End Rule)

๐ŸŽข

Peak-End Rule

People judge an experience by its peak and how it ends.

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Peak-End Rule definition

Users don't merely evaluate an experience based on the average or a sum of all the micro-experiences. Instead, their brain heavily weighs the peaks (high or low) and the end of the experience. Peaksโ€”when pleasantโ€”often correspond to memorable delighters sprinkled into the user journey.

Peak-End Rule examples

  1. After you pay to upgrade your account, Zapier shows animated confettis as a way to celebrate (and rightfully take your focus away from the hundreds of dollars you just paid!):

  2. Duolingo doesn't provide a clear exit point. This makes the "end" of your in-app experience feel like you're abandoning your learning process (even if you've achieved your goal):

๐Ÿ‘…

Sensory Appeal

Users engage more with things appealing to multiple senses

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Sensory Appeal definition

Why are we tempted to eat sweets when walking by a bakery in the morning? The smell out of the oven is strong enough to make us stop. The sights, sounds, feels, tastes, and smells of products are designed to engage users' senses. And when multiple senses are engaged, people are more likely to create an emotional connection with the brand.

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Zeigarnik Effect

People remember incomplete tasks better than completed ones

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Zeigarnik Effect definition

Lewinโ€™s field theory states that a task in progress creates task-specific tension. This tension is relieved when the task is completed, but if the task is interrupted, it stays. That tension makes relevant information more accessible and more easily remembered.

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Endowment Effect

Users value something more if they feel it's theirs

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Endowment Effect definition

Users are more likely to want to keep something that they own than acquire that same thing when they don't own it. They tend to overvalue the things they own, regardless of their objective market value. (Related: Loss Aversion)

Endowment Effect examples

  1. Trello encourages you to personalize your board through a well-timed nudge so that you perceive it more like "your" workspace:

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Chunking

People remember grouped information better

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Picture Superiority Effect

People remember pictures better than words

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Method of Loci

People remember things more when they're associated with a location

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Shaping

Incrementally reinforcing actions to get closer to a target behavior

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Delighters

People remember more unexpected and playful pleasures

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Internal Trigger

When users are prompted to take action based on a memory

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Recognition Over Recall

It's easier to recognize things than recall them from memory

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Storytelling Effect

People remember stories better than facts alone

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Negativity Bias

Users recall negative events more than positive ones

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Availability Heuristic

Users favor recent and available information over past information

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Spacing Effect

People learn more effectively when study sessions are spaced out

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Serial Position Effect

It's easier for users to recall the first and last items of a list

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Product & Psychology Resources

If you want to learn more about behavioral psychology and mental models, we highly recommend you take a look at these resources:

๐Ÿ““

Cognitive Biases Codex

The four categories of our list come from Buster Benson's work

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description

Buster Benson. He did an impressive job with the categorization of cognitive biases which led him to build a massive Codex.

The four categories of this list are based on his research, so we want to make sure he gets the credit for this hard work.

Buster Benson
Every single person, including myself, has many implicit associations that lead to bias that they can't fully eradicate in themselves. It's more effective to accept that fact, and account for it by being transparent about it, than to try to hide it.
โ€” Buster Benson, author of "Why Are We Yelling?"

๐Ÿ“˜

Super Thinking

The big book of mental models and cognitive biases (Gabriel Weinberg)

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description

Gabriel Weinberg(CEO of DuckDuckGo), co-authored a WSJ bestseller book that inspired us a lot: Super Thinking: The Big Book of Mental Models.

He recently did a video interview with Jordan Harbinger where he discussed the importance of mental models and cognitive biases. We completely agree with him when he says:

Gabriel Weinberg
Knowing the names of cognitive biases and mental models is important. That's because once you have a name for something, you can start to spot it in the real-world. And once you start to spot it, then you can really start to use the tools [and reap the benefits].
โ€” Gabriel Weinberg, CEO of DuckDuckGo

๐Ÿ“™

Hooked

How to build habit-forming products (Nir Eyal)

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description

This book dives deep into the psychology of habits. It's filled with user retention loops and examples.

Nir Eyal is the best-selling author of Hooked: How To Build Habit-Forming Products and Indistractable.

He's doing amazing work at the intersection of psychology, technology, business and ethics.

๐Ÿ“•

Influence

The psychology of persuasion (Robert Cialdini)

Coming Soon
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Predictably Irrational

The hidden forces that shape our decisions (Dan Ariely)

Coming Soon

Cognitive Biases Cheat sheet

We took the time to summarize each principle in one line.

They are all in a free cheat sheet of cognitive biases principles.

You can download this cheatsheet as a PDF here.

Use it as a user empathy reminder while you build a feature.

Nir Eyal
We all have a responsibility to build ethically-designed products and services to improve people's lives. Growth.Design's list of cognitive biases and psychological principles is a great reference for any team committed to improving their customers' user experience. Dan & Louis-Xavier's comic book case studies show you how.
โ€” Nir Eyal, bestselling author of Hooked and Indistractable

Now Itโ€™s Your Turn

So which principle are you going to try next?

Are there missing elements we should add to the list?

You can reach us at team@growth.design, we reply to everyone!