Every time users interact with your product, they:
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. Let’s dive right in.
PS: Don't have time to read the whole list? Just get the cheat sheet.
Users filter out a lot of the information that they receive, even when it could be important.
More options leads to harder decisions
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.
Trello's 3rd signup step has a dropdown with 15 options. That makes it hard to pick one:
Duolingo's list of lessons can sometimes be overwhelming:
Zapier showed too many navigation links during their upgrade flow which distracts you from crucial checkout steps:
In a travel booking app like Airbnb, having too many options can lead to a paradox of choice (and a churn!):
People look for evidence that confirms what they think
People tend to search for, interpret, prefer, and recall information in a way that reinforces their personal beliefs or hypotheses.
In times of crisis it's hard not to look for what we want to believe in:
Previous stimuli influence users' decision
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.
The friendly-looking airport landscape lets the users dream about their next trip increasing the chances of a positive experience:
Superhuman's onboarding includes a priming on the fact that you'll receive some helpful onboarding emails from their CEO
Anti-Example: Tinder misses a great opportunity to prime new singles during the onboarding:
Total amount of mental effort that is required to complete a task
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 user’s ability to handle it, the cognitive load is too high.
Users rely heavily on the first piece of information they see
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.
Tinder's pricing table shows the most expensive subscription plan first (the anchor) so that the other plans look inexpensive in comparison:
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.
Subtle hints can affect users' decisions
Users are less overwhelmed if they're exposed to complex features later
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.
Large and close elements are easier to interact with
Users' thoughts filter what they pay attention to
People underestimate how much emotions influence user behaviors
Elements used to guide users' eyes
People remember more items that stand out
The order in which people perceive what they see
People filter out things from their environment when in focus
People neglect things that don't make it past a selection process
Users tune out the stuff they get repeatedly exposed to
Elements that are close and similar are perceived as a single unit
Elements that communicate what they will do
Users' attention is drawn to higher visual weights
When the information on what to do next is within the prompt itself
Create a new option that's easy to discard
People tend to choose the middle option in a set of items
The way information is presented affects how users make decisions
Elements close to each other are usually considered related
If you simplify too much, you'll transfer some complexity to the users
Users are more likely to take action when the effort is small
When users take action, feedback communicates what happened
People tend to be influenced by their own expectations
People perceive designs with great aesthetics as easier to use
When users try to give sense to information, they make stories and assumptions to fill the gaps.
Users adapt their behaviors based on what others do
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.
Entice users to take action by showing the number of people who did it, like Calm does:
For pricing pages, social proof is often used to represent the most popular package just like in Tinder's "rewind" upsell:
Amazon shows the most common choice of previous buyers like yourself:
Airbnb shows the most popular filters per destination, but that can sometimes back-fire:
Spotify's podcast didn't include social proof, making it hard to know if an episode was worth your time:
People value things more when they're in limited supply
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!
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:
Dark Pattern: Mario Kart offers Tours and special items for a limited time to increase conversion rates:
Dark Pattern: Sleepzy uses unjustified scarcity to pressure new users into buying:
Users have a desire to seek out missing information
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.
Users have a preconceived opinion of how things work
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.
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":
People prefer familiar experiences
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.
People judge things (or people) based on their feelings towards one trait
Users can only keep 5±2 items in their working memory
One unit of something feels like the optimal amount
Being fully immersed and focused on a task
Users adapt more easily to things that look like real-world objects
People feel the need to reciprocate when they receive something
Users attribute more importance to the opinion of an authority figure
Tasks that are part of a group are more tempting to complete
People enjoy rewards, especially unexpected ones
Individual items seem more attractive when presented in a group
Not realizing that people don't have the same level of knowledge
When new users first realize the value of your product
Users are more likely to interact with prompts they setup for themselves
Users tend to skew survey answers towards what's socially acceptable
It's painful to hold to opposing ideas in our mind
Motivation increases as users get closer to their goal
When users know what to expect before they take action
Simple solutions are often better than the more complex ones
Users tend to prefer socially responsible companies
People overestimate their ability to predict outcomes after the fact
Users perceive a relationship between elements that look similar
Users interpret ambiguous images in a simpler and more complete form
People tend to believe they are being noticed more than they really are
Users are more likely to take action if there's a feeling of new beginnings
Users are busy so they look for shortcuts and jump to conclusions quickly.
People value things more when they see the work behind them
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).
KAYAK (travel booking site) once delayed the time search results page to show that it is "crunching data".
TurboTax showed "validation and analysis" screens when you submit your taxes.
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:
Users tend not to change an established behavior
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.
Amazon uses status quo bias to encourage behaviors that aren't necessarily to the user's advantage:
Some Airbnb filters are OFF by default, which can lead to confusion as to what will happen if you switch them ON:
When users invest themselves, they're more likely to come back
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.
People prefer to avoid losses more than earning equivalent gains
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)
Your fear of losing the Duolingo gems you wager encourages you to maintain the practice streak to which you committed:
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:
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:
Users tend to be consistent with their previous actions
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.
Tinder's onboarding splits their signup form in 6 single-question steps to leverage the power of micro-commitment:
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%.
Duolingo email notifications cleverly use the fact that you committed to practice a language to ask you if you "still want to learn it":
Users are reluctant to pull out of something they're invested in.
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.
Duolingo encourages you to bet gems if you think you can keep a practice streak for one week:
Netflix: Have you ever watched a boring movie until the end, simply because you started it? That's sunk cost fallacy in action.
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.
Making a lot of decisions lowers users' ability to make rational ones
Users are less likely to adopt a behavior when they feel threatened
When researchers' biases influence the participants of an experiment
Users adapt better to small incremental changes
If all you have is a hammer, everything looks like a nail
Hard tasks are less scary when coupled with something users desire
The time required to complete a task will take as much time as allowed
People tend to overestimate their skills when they don't know much
People's current emotions cloud and influence their judgment
People tend to prioritize immediate benefits over bigger future gains
People spend more when they can't actually see the money
People take credits for positive events and blame others if negative
Roughly 80% of the effects come from 20% of the causes
The ease with which users can discover your features
When people's convictions are challenged, their beliefs get stronger
People overestimate how much other people agree with them
When you believe that generic personality descriptions apply specifically to you.
When user partially create something, they value it way more
People tend to underestimate how much time a task will take
Users try to remember what's most important, but their brain prefers some elements over others.
Invite users to leave your app at the right moment
People judge an experience by its peak and how it ends.
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. Peaks—when pleasant—often correspond to memorable delighters sprinkled into the user journey.
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!):
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):
Users engage more with things appealing to multiple senses
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.
People remember incomplete tasks better than completed ones
Lewin’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.
Duolingo shows you an incomplete progress bar to encourage you to reach your daily practice goal:
Users value something more if they feel it's theirs
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)
People remember grouped information better
People remember pictures better than words
People remember things more when they're associated with a location
Incrementally reinforcing actions to get closer to a target behavior
People remember more unexpected and playful pleasures
When users are prompted to take action based on a memory
It's easier to recognize things than recall them from memory
People remember stories better than facts alone
Users recall negative events more than positive ones
Users favor recent and available information over past information
People learn more effectively when study sessions are spaced out
It's easier for users to recall the first and last items of a list
The four categories of our list come from Buster Benson's work
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.
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.— Buster Benson, author of "Why Are We Yelling?"
The big book of mental models and cognitive biases (Gabriel Weinberg)
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:
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].— Gabriel Weinberg, CEO of DuckDuckGo
How to build habit-forming products (Nir Eyal)
The psychology of persuasion (Robert Cialdini)
The hidden forces that shape our decisions (Dan Ariely)
We took the time to summarize each principle in one line.
They are all in a free cheat sheet of cognitive biases principles.
Use it as a user empathy reminder while you build a feature.
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.— Nir Eyal, bestselling author of Hooked and Indistractable
So which principle are you going to try next?
Are there missing elements we should add to the list?
You can reach us at email@example.com, we reply to everyone!