18 Cognitive Biases You Can Use for Conversion Optimization

Cognitive Biases

Persuading completely rational people to make a rational decision or take a rational action would be easy. Unfortunately, you’re stuck dealing with irrational thinking, fueled by cognitive biases and emotions.

So, how do you persuade effectively when people are so heavily influenced by subjective (and contextual) factors?

That’s a complicated question with no definitive answer. Fortunately, the first step to answer that question for your audience is becoming aware of those subjective (and contextual) factors.

What is cognitive bias?

Cognitive bias is the tendency to think certain ways, often resulting in a deviation from rational, logical decision-making. It’s studied most often in psychology and behavioral economics, but it’s present in all areas of life.

Cognitive biases impact how we buy, sell, interact with friends, think, feel, etc.

If you’re feeling guiltier about a certain situation than you should, according to friends and family, you’re experiencing egocentric bias. If you’ve just started a new freelance career and feel “imposter syndrome” creeping in, you’re experiencing the worse-than-average effect.

Often, we’re unaware of our own cognitive biases and how they impact our lives.

Why should you care about cognitive biases?

Cognitive biases affect how visitors think and feel about your site and company. They affect how likely visitors are to convert to leads. They affect how likely visitors are to share or talk about your product or service.

Of course, cognitive biases also affect you. They affect your ability to run rational tests, analyze test results, sample without pollution, etc.

Disagree? That’s your bias blind spot, which allows you to view yourself as less biased than other people.

Once you’re aware of cognitive biases, you can begin to account for them and limit their impact on your visitors’ thinking—and your own.

18 cognitive biases that affect your marketing

You can find a complete list of cognitive biases on Wikipedia. While some are more directly applicable to CRO than others, it’s worth taking the time to read about all of them. For now, let’s start with some of the most common.

Cognitive Bias Comic

1. Anchoring

The tendency to rely too heavily, or “anchor,” on one trait or piece of information when making decisions (usually the first piece of information that we acquire on that subject).

Talia Wolf explains:

So much of our decision making is governed by how information is presented. A $40 pricing plan might sound like a lot on its own, but using an anchor can help you put things into perspective for prospects.

How it affects you and how to use it:

  • If your first encounter with A/B testing is a button color change that increased conversions (that’s your anchor), you’re less likely to try other A/B tests, especially radical redesigns.
  • If your visitor first encountered a competitor’s product priced at $49 per month (that’s their anchor), they’re less likely to accept your $69 per-month price.
    • Use this bias to command the price you want for your product (e.g., “$60/month value, now $45/month.”)
  • If your visitor has a negative impression of your brand (that’s their anchor), whether it’s from word of mouth or previous experience, they’re less likely to buy from you in the future.

2. Attentional bias

The tendency of our perception to be affected by our recurring thoughts.

As Bart Schutz details:

The Attentional bias is our tendency to pay more attention to emotionally dominant stimuli, and to neglect other relevant data when making decisions. So the more something touches us, the more attention we pay to it.

Imagine you have an anxiety for spiders (you’re arachnophobic). Now I ask you to do “The Stroop Test”: in this test, I confront you with rows of words that are printed in different colors (e.g., red, green, yellow, and blue). All you have to do is name the color (not pronounce the word).

A consistent finding in Stroop studies with anxious patients is that their color naming of threatening words (spider, arachnid, spinner, tarantula, etc.) is slower than that of neutral words, and slower than with non-anxious patients. This is because it’s harder not to pay attention to emotionally dominant stimuli.

How it affects you and how to use it:

  • Familiarity can go a long way. The more often a person sees your name, logo, or call to action, the more likely they are to purchase from you.
  • Place calls to action throughout your landing pages, pay to retarget your visitors with ads, tweet and Facebook regularly, (guest) blog consistently, etc.
  • Be aware of how this might impact your decisions as an experimenter. The more often you see a certain test in case studies, for example, the more likely you are to blindly believe that test will be applicable to your site.

3. Availability cascade

A self-reinforcing process in which a collective belief gains more and more plausibility through its increasing repetition in public discourse (or “repeat something long enough, and it will become true”).

BuzzFeed and Availability Cascade.

How it affects you and how to use it:

  • This goes hand-in-hand with attentional bias. The more people talk about your site in a positive way, the more likely they are to purchase from you. Conversely, the more people talk about your site in a negative way, the less likely they are to purchase from you.
  • Spend time refining your messaging, story, and copy. What combination of those three things will result in more positive conversations about your site? Next, make it easy for people to start those conversations (e.g., social sharing buttons, offer content for a tweet vs. an email, submit content to social bookmarking sites, etc.)
  • Find the influencers and media outlets that will help you extend your reach as much as possible via their sites and social networks. Provide them with everything they need (topic ideas, story ideas, relevant industry trends, facts and figures, click-to-share links, etc.) to promote your site.

4. Backfire effect

When people react to disconfirming evidence by strengthening their beliefs.

How it affects you and how to use it:

  • Your visitors believe what they believe, and all the factual evidence in the world won’t change their mind. Instead, you need to rely on emotional persuasion. Appealing to rationality won’t change deeply held beliefs (e.g., Apple is better than PC, Basecamp is better than Trello, Google Sheets is better than Excel, etc.)
  • If you are too attached to a hypothesis, you may experience this effect as well. Despite evidence that your hypothesis was wrong, you’ll come up with reasons why the test was invalid or incorrect. Running double blind tests can help with this issue, to some extent.
  • Using qualitative research, get to the heart of your visitors’ beliefs. How do they address money-related decisions? What are their thoughts on productivity and work-life balance? How do they feel about being marketed to? Once you know your visitors’ core beliefs, you can work within them instead of trying to change them.

5. Bandwagon effect

The tendency to do (or believe) things because many other people do (or believe) the same. Related to groupthink and herd behavior.

basecamp homepage showing the bandwagon effect.
For years, Basecamp has highlighted the growing number of sign-ups on its homepage.

How it affects you and how to use it:

  • If your visitor thinks everyone else is using your product or service, they’re more likely to use your product or service. That’s why creating scarcity and social proof are so effective.
  • Identify a niche community and the influencers leading that community. Begin seeding your product or service to that community, creating a group mentality within that niche. Once you’ve won them all over, identify another niche community.
  • Near points of friction (e.g., call to action, checkout pages), add social proof in the form of numbers (e.g., “1 million happy customers”) and testimonials (“I love Site XYZ because ABC.”)
  • If you associate with marketers who believe changing a button color will dramatically impact conversions, you’re more likely to believe that changing a button color will dramatically impact conversions as well. Be aware of who might be influencing your tests without your knowledge.

6. Belief bias

An effect where someone’s evaluation of the logical strength of an argument is biased by the believability of the conclusion.

Axe and Belief Bias.

How it affects you and how to use it:

  • When you make extraordinary claims, regardless of whether they’re true, visitors are less likely to purchase from you. If it sounds “too good to be true,” visitors will believe that, well, it is too good to be true.
  • Show visitors how your product or service will improve their lives, not how awesome your product or service is itself. Be sure that even those claims aren’t too far fetched (e.g., if you spray yourself with Axe, you’ll instantly become a Casanova).

7. Clustering illusion

The tendency to overestimate the importance of small runs, streaks, or clusters in large samples of random data (that is, seeing phantom patterns).

How it affects you and how to use it:

  • You’re likely to spot trends where there are none, which results in future tests and hypotheses based on false information. To avoid this, be sure you’ve calculated the correct sample size prior to beginning your test. Do not stop the test until you’ve reached that full sample size.
  • Once you believe you’ve spotted a trend, you begin looking for it subconsciously. In doing this, you ignore other, likely more valuable, insights.

8. Confirmation bias

The tendency to search for, interpret, focus on, and remember information in a way that confirms one’s preconceptions.

Roger Dooley writes about what confirmation bias reveals:

There’s a lesson here for all of us—to avoid making bad decisions about investments, political candidates, and many other topics, we must do two things:

1. Be aware of the danger of confirmation bias, and acknowledge that our judgment can be clouded by it.

2. Aggressively seek out and understand information that disagrees with our existing belief.

How it affects you and how to use it:

  • In a way, this is similar to the clustering illusion. Once you have an idea in your head, you subconsciously begin to seek out information that confirms that idea or belief. As an experimenter, this could mean a lot of wasted time on insignificant tests.
  • If you believe reducing form fields increases conversions and it does, even marginally, you’ll likely call the test a success and move on—missing other valuable insights and neglecting more significant tests.
  • You could even interpret data the wrong way merely to confirm your idea or belief. Before you run a test, try to eliminate any emotional attachment to a result. Remind yourself that your opinion is, in fact, only an opinion.
  • Your visitors also have preconceptions, which are difficult to change. For the best results, cater to those preconceptions through familiarity and consistency (instead of trying to alter those ideas and beliefs).

9. Contrast effect

The enhancement or reduction of a certain perception’s stimuli when compared with a recently observed, contrasting object.

Limpfish and Contrast Effect with a humorous 404 page.
Limpfish used a funny 404 page to add an element of surprise.

How it affects you and how to use it:

  • While you must meet “basic expectations,” you must also create contrast. Surprising stimuli cause the brain to slow down, focusing on the stimuli and committing it to memory as a result.
  • Think about custom 404 pages, Easter eggs in apps and movies, etc. They still meet the basic expectations of their categories, but they provide a few surprising elements to stand out from the crowd.
  • Our brains are always comparing: your site to competitor sites, your current site to a previous design. Though risky, radical redesigns can be especially powerful because of the contrast effect, helping you overcome the local maximum.

10. Curse of knowledge

When better-informed people find it extremely difficult to think about problems from the perspective of lesser-informed people.

How it affects you and how to use it:

  • You are not your visitors. You have become so familiar with your site that you can no longer use or view it the way a new visitor would. When redesigning to increase conversions, don’t make the decisions yourself. Ask someone else—someone less informed—to think about the UX and design.
  • The way you describe your product or service is likely more advanced than the language your visitors would use. Have a less-informed copywriter craft your messaging or conduct qualitative research to discover how current customers describe your product or service.

11. Empathy gap

The tendency to underestimate the influence or strength of feelings, in either oneself or others.

WorkSafe and Empathy Gap.
Emotions are used to persuade more often than we realize.

How it affects you and how to use it:

  • You underestimate the role emotions play in decision-making (with yourself and others). We believe that we’re rational people making rational decisions.
  • Craft emotional copy, use emotional design/UX, create an emotionally persuasive call to action. Each is more convincing than an appeal to logic alone. Don’t try to persuade rational visitors—you don’t have any.
  • Be aware that your own emotions impact conversions. You hypothesize based on emotions, you believe your visitors’ emotions are reflective of your own, etc.
  • You can’t get rid of emotions, but you can conduct qualitative research to understand the emotions associated with your site and brand, then design emotionally persuasive arguments based on that information.

12. Framing effect

Drawing different conclusions from the same information, depending on how that information is presented.

Joanna Wiebe details the origins and importance of framing:

Framing as we know it today is based on studies done in the early 80s by Tversky & Kahneman, from which marketers have gleaned the following insights:

  • Negative messages carry negative associations, and positive messages carry positive associations
  • Losses are more painful than gains are gratifying (i.e., “loss aversion”)
  • Small gains on small investments are more gratifying than equivalent large gains on large investments (e.g., “Save $2 when you spend $10” is better than “Save $1000 when you spend $5000”)
  • A sure win is preferable to a possible win (i.e., “certainty effect”)
  • A possible loss is preferable to a definite loss (i.e., “pseudocertainty effect”)

How it affects you and how to use it:

  • If you’re conducting qualitative research, the questions that you ask are subject to this effect. The way you ask a question can lead to very different results. Before publishing a survey or asking even a single question, ensure the language is clear and you’re not leading the respondents to a certain answer.
  • In terms of copy and design, how you present your value proposition and call to action is just as important as what your value proposition and call to action are. Will you use data to persuade? Will you ask questions to inspire deep thinking? Will you tell a story? Be sure you guide every visitor to the same conclusion.
  • How you present conversion data to the rest of your team is also impacted. If you’re not clear and concise, your colleagues may draw very different conclusions about the effectiveness of your test and the insights learned.

13. Illusory correlation

Inaccurately perceiving a relationship between two unrelated events.

How it affects you and how to use it:

  • As you learned with the clustering illusion, our brains look for trends and patterns, often identifying connections where there are none. This can impact your test results and your ability to analyze/report them accurately.
  • If you run a test and conversions increase, you might perceive a relationship between those two events (i.e. your test is the reason conversions increased). In fact, conversions might have increased because of a validity threat like a PPC campaign or a seasonal change.
  • Before coming to conclusions about your data, consider external factors that could influence your tests. A holiday? A new paid campaign? A certain day of the week? Train your brain to look for meaningful connections that offer real insight, not just connections in general.
  • Whenever you run a test, make sure you reach statistical significance with a large enough sample. If you don’t, your test results will be invalid, and you’ll make connections between unrelated, unreliable events.

14. Post-purchase rationalization

The tendency to persuade oneself through rational argument that a purchase was a good value.

How it affects you and how to use it:

  • Are you familiar with the term “buyer’s remorse”? More than 50% of people often or sometimes feel buyer’s remorse. When it kicks in, your visitors persuade themselves, with rational arguments, into believing the purchase was a good idea.
  • In your post-purchase messaging (on-page and via email), use positive words that signal a successful purchase and reinforce the value proposition. After the conversion, you aren’t done persuading.
  • Also, be aware that rationalization is a common function of the brain. Your visitors are, more often than not, making decisions based on their emotions and rationalizing those decisions later. Appeal to emotion!

15. Unit bias

The tendency to want to finish a given unit of a task or an item. Strong effects on the consumption of food in particular.

How it affects you and how to use it:

  • Consider how many bad movies and books you’ve finished simply because you started. Once you begin, you feel inclined to finish. This is why storytelling is so powerful. Structure your copy to include a beginning, a middle, and an end to improve readability and time on page.
  • Go through your conversion funnel. Are there steps that make completion more difficult than it needs to be? Eliminate unnecessary form fields, simplify language, make designs more intuitive, etc. Your visitors want to finish what they’ve started, but you have to make it as easy as possible.

16. False consensus effect

The tendency for people to overestimate the degree to which others agree with them.

How it affects you and how to use it:

  • No one clicks on pop-ups.” “Everyone hates sliders.” Do these phrases sound familiar? We tend to believe that others think the same way we do, agreeing with us more often than not. This can negatively impact the way we design, write copy, etc.
  • When conducting qualitative research, don’t overvalue individual or small-group opinions. Those opinions are not representative of your entire audience. Each person has their own biases, and it’s unsafe to assume everyone feels the same way.
  • Everything you do to increase conversions must be done because data indicates that it works, not because it’s your personal opinion. Your personal opinion is, well, personal. What’s annoying and intrusive to you is helpful and eye-opening to someone else.

17. Context effect

That cognition and memory are dependent on context, such that out-of-context memories are more difficult to retrieve than in-context memories (e.g., recall time and accuracy for a work-related memory will be lower at home, and vice versa).

How it affects you and how to use it:

  • If you’re trying to play on visitors’ past memories or behaviors, context is important. Those feelings are easier to recall when they’re in the same context as they were previously. Use your copy and design to set the stage and make retrieving those feelings, memories, and behaviors easier.
  • If you’re crafting a value proposition and don’t provide context to help visitors retrieve memories, you’ll run into problems. Say you solve the problem of note taking during business meetings, but your visitors aren’t at work or in a meeting. Remembering how difficult/annoying taking notes is may seem a distant memory. Use context (e.g., images, keywords) to bring that memory to the forefront.
  • Consider how this can be used in PPC advertising. If you want to solve a business problem, target people during business hours. Target people who are in the best context to make the decision you want them to make.

18. Humor effect

That humorous items are more easily remembered than non-humorous ones, which might be explained by the distinctiveness of humor, the increased cognitive processing time to understand the humor, or the emotional arousal caused by the humor.

Lance Jones offers guidelines for landing pages:

Your landing page visitors need to understand (1) where they are, (2) what they can do on your site, and (3) why they should stick around. If you’re at all unclear about any of these things, you’ll lose credibility and the visitor.

But once you have the essential messages in place (and as clear as Voss water!), it’s okay to have some fun and let the creative juices flow.

How it affects you and how to use it:

  • What do Dollar Shave Club, Poo-pourri, and this £8,999 urine-free wetsuit all have in common? They use the humor effect to be more memorable and capture attention.
  • Think about how many times you say something like, “I saw the funniest thing…” Humor spreads like wildfire.
  • Humor can work well, but be careful. Trying to be funny or clever often sacrifices clarity.
    Focus on making the where, what, and why crystal clear.
    Once that’s done, you can experiment with humor (e.g., add a punchline in your copy, insert a GIF, use a meme maker to create a shareable image, or experiment with a witty tagline).


There are dozens of other cognitive biases to consider, but these are some of the most common and relevant to marketers and optimizers.

Now that you’re aware of them, you can begin to answer the original question: How do you persuade effectively when people are so heavily influenced by subjective (and contextual) factors?

The more aware you are of the brain’s limitations, the more persuasive you’ll be. Here’s what you need to know (and do) about cognitive biases:

  1. Everyone is affected by cognitive biases, even you.
  2. Be aware of the different biases and try to spot them in your day-to-day life.
  3. Understand that you and your visitors are much less rational and more emotional than you’d like to think.
  4. Begin using cognitive biases to your advantage in your copy, design, and calls to action.
  5. Begin accounting for your own cognitive biases when you run tests.

Related Posts

Join the conversation Add your comment

  1. Thanks for the 18 Cognitive Biases.
    Bookmarked this, for future reference.

    1. Avatar photo

      Thanks Azizul! Glad you found it helpful.

      Let me know if you have questions!

  2. Hi Shanelle,

    This post is so useful with some memorable applications of the principles (I particularly like the wetsuit example!) that I was going to print it off and pin it on the wall. Then I realized my ceilings are too low to paste it floor to ceiling. Have you got a more detailed cheat-sheet than the little summary you give here?

    1. Avatar photo

      The wetsuit ad is still as funny as the day I first read it.

      So glad you liked the article! Thanks for the kind words.

      I don’t have one right now, but I’ll see what I can do.

  3. Fascinating article! I noticed some of my own biases coming out even as I was reading and looking at the Ad examples. It’s amazing how bias we are–and we don’t even think we are! Definitely think this is worth paying attention to when growing your brand and business. We can be so much more effective when we think how our clients would think. Thanks for sharing this and for laying it out piece by piece for us!

    1. Avatar photo

      Thanks Lynan! The easiest way to understand biases is to begin recognizing them in our own decision-making processes.

      Glad I could help.

Comments are closed.

Current article:

18 Cognitive Biases You Can Use for Conversion Optimization