Jeremy Smith Feb 19, 2019 11:25:36 AM 32 min read

The Surprising Science of Cognitive Fluency and Its Explosive Impact on Conversion Optimization

As a psychology nerd, I have a fascination with issues like cognitive fluency.

Such terms may be uninteresting to the proverbial man on the street, but conversion optimizers are another breed. We live and breathe the arid air of neuroscience, optimization, split testing, and the other dark arts of persuasion.

And for conversion optimization, cognitive fluency is a very big deal.

I intend to explain exactly why and how cognitive fluency is significant in conversion optimization.

Cognitive fluency is “the ease with which information is processed.”

Let’s start where all good lessons begin — with definitions. (For what it’s worth, cognitive fluency often goes by another name — “processing fluency.”)

What is cognitive fluency?

The man-on-the-street definition is best. Here’s how The New York Times defines it:

A measure of how easy it is to think about something.

definition of cognitive fluency

The Boston Globe also reports on cognitive fluency, and features this definition:

Cognitive fluency is simply a measure of how easy it is to think about something

The Globe makes the concept simpler with this straightforward mathematical / verbal definition of cognitive fluency.

Easy equals true

Easy = true is a great way to sum up the idea of cognitive fluency. Although such a raw equation is tragically without nuance, it points up one of the gleaming facets in the field of cognitive fluency — the mere-exposure effect, which we’ll get to later.

For now, the core idea is that cognitive fluency has to do with how easy or hard it is to intake and process informational stimuli.

Cognitive fluency helps to define the difference between simplicity and complexity. Like so ...

simplicty vs complexity

To visualize the idea further, let me show you how cognitive fluency affects our ability to intake information. I’ll use the simple example of font choice.

Which of the two messages above is easier for you to read?

Obviously, the left one. Why? Because cognitive fluency.

On a deeper level, I could tell you all about the color choice, contrast ratios, kerning, serifs, pixels, squares, and other stuff, but I don’t need to. Why? Because the human brain immediately grasps cognitive fluency without a whole lot of training and understanding.

Here’s another example:

The examples above show you how cognitive fluency works with verbal material, but the concept is much broader than just typeface and color.

Here’s how the difference between verbal and graphic produces enhanced cognitive fluency.

Which is easier to understand? A description of a circle, or a picture of a circle?

Simple. Cognitive fluency tells us that the blue circle on the right wins the day.

Cognitive fluency is rather simple, really. And there’s no need to go unnecessarily long with a bunch of psychological research and theoretical forays into the leading-edge neuroscientific research on the subject. (Even though it would be fascinating.)

How is fluency created and affected?

Let me ask a couple of questions (and then answer them): How does a user interpret fluency? What influences affect an individual’s ease of processing information?

For example, what if an individual has seen only script-style fonts their entire life? All they read is script. All they use is script. All their reading involves a light blue font on a peach background. They have no experience with serif or sans-serif typefaces, and are trained to read scripted fonts with ease and expertise.

Then, they look at this image:

Which of the two would be superior in terms of cognitively fluency?

It would probably be the one on the right.

The perceptions of cognitive fluency are known as “attribution.” Princeton University’s Daniel Oppenheimer described the impact of attribution:

This attribution process can cause fluency to have diametrically opposing influences on judgment.

One person’s attribution of cognitive fluency can be totally different from another’s attribution.

To sum up, there will be differences in customer A’s cognitively fluent experience, compared with customer B’s interpretation of the same website, landing page, or CTA.

What are those influences?

Past Experience.

If a user has seen your site before, heard of the brand, seen a similar template, or clicked on similar CTAs, then their cognitive fluency will be higher when they view your site.

If you’ve shopped, then you’re familiar with that yellow CTA button:

the famouse Amazon yello CTA button

The fluidity of the cognitive processing causes your brain to attribute judgments of familiarity and safety. You know the button. It’s familiar. You have past experience with it.

Current Context

Every website has contextual clues that affect fluency.

Sometimes, the context can be as straightforward as visual clutter. Ling’s cars, for example, has a ton of junk on it. I can hardly believe my eyeballs.

Lings cars

(Visit the website to get the full impact.)

The clutter negatively impacts my cognitive fluency, making it difficult for me to identify what to do, how to do it, and the potentially dangerous repercussions of doing it.

Based on the current context, I’m skeptical. There’s a lot of friction. I do not trust.

Plus, past experiences come into play. This website is similar to other websites that I have accidentally stumbled upon that included undesirable images, or required me to delete my browser history.

There are more influences, however. Psychologists Alter and Oppenheimer have created the following list, identifying the various “faces of fluency.” You can think of this list as interpretational filters upon fluency:

  • Perceptual fluency
  • Conceptual fluency
  • Linguistic fluency
  • Retrieval fluency
  • Encoding fluency
  • Embodied fluency
  • Decision fluency
  • Spatial fluency
  • Deduction-based fluency
  • Generative fluency
  • Attentional fluency.

Obviously, such a vast array of fluencies combined with the vast variety of potential customers is going to affect the user’s fluency or lack of fluency in any given conversion context.

Basically, fluency is in the cognition of the beholder. (Kind of like “beauty is in the eye of the beholder,” only better.)

So what should we do about it?

Here comes my ever-beaten drum: Know your customer.

Know their motivations, their drives, their desires, their demographics, their psychographics, their all.

And … know your customer’s cognitive fluencies.

Cognitive fluency affects conversion optimization in several significant ways.

I’m now diving into the section of this article that deals with the impact of cognitive fluency upon conversion optimization.

Cognitive fluency affects how customers judge their experience with your website.

Psychologists concur on this critical point: Cognitive fluency has a profound and tremendous effect on judgment.

Judgment is at the core of conversion optimization. ClickZ points out that, regardless of the conversion context, “consumers [display] similar patterns of judgment.”

Cognitive fluency and conversion cohere in this nexus of judgment.

A bunch of geniuses agreed that processing fluency (another term for cognitive fluency) affects judgment:

The Hedonic Marking of Processing Fluency

The “judgment” we’re talking about is as simple as a customer deciding whether something is true or false.

Christian Unkelbach, at the Psychologisches Institut, Universität Heidelberg, writes this:

Fluently processed statements are judged to be true, fluently processed instances are judged to be frequent, and fluently processed names are judged to be famous.

That’s why Apple can produce a cognitively fluent page, and people believe what the page says. They perceive as truth the claims that Apple makes.

Just look at this page featuring the Apple watch:

iwatch ad

The human brain rapidly transmits the aesthetic visual layout, the svelte products, the minimalist design, and the easy-to-read font. In other words, this page has high cognitive fluency.

Thus, the customer is highly likely to see that phrase — “To wear it is to love it” — and interpret it as true. They believe it.

Remember the Boston Globe, and their easy = true idea? That’s what’s going on here. It is easy to understand, to look at, to process, to see. Therefore it is true.

Cognitive fluency affects the customer’s willingness to make a decision to convert.

The Boston Globe explains the far-reaching impact of cognitive fluency with this apt observation:

Because it shapes our thinking in so many ways, fluency is implicated in decisions about everything from the products we buy to the people we find attractive to the candidates we vote for — in short, in any situation where we weigh information.

The point is, cognitive fluency affects decision making. The author of the article, Drake Bennett, goes on to point out,

Advertisers, educators, political campaigners, or anyone else in the business of persuasion can use these findings.

Hey, he’s describing us — you, me, conversion optimizers!

Aesthetic pleasure and beauty increase the likelihood of a conversion.

How ugly or pretty something is will have an impact on conversions. Basically, an ugly website will have poor cognitive fluency, and therefore low conversions. A pretty website will have high cognitively fluency and therefore high conversions.

The mere-exposure effect comes into play here.

The mere-exposure effect is a psychological phenomenon by which people tend to develop a preference for things merely because they are familiar with them. In social psychology, this effect is sometimes called the familiarity principle.

Familiarity and beauty are closely linked. The more often we see a person, the more familiar they become to us. We develop some level of attraction toward another person, not simply because of the objective measure of that individual’s beauty, but simply due to the subjective experience of familiarity that we have with them.

The mere exposure and its aesthetic implications hold true in design and conversion optimization.

Yesterday’s web was far from aesthetic. I mean, seriously, look at this ...

Today, however, entire industries are devoted to making the web beautiful.

a modern website design

Let me use another Apple example, not because I own any stock in the company, but because they do a good job of featuring cognitive fluency in their marketing.

Notice how the Apple Watch TV ad features cognitive fluency:

There are no words until the very end of the ad. Your mind doesn’t have to listen to someone talking and reading words and process images. All you have to do is allow your mind to be influenced by the emotion-affecting music, and watch the pretty watches float around the screen.

Your brain’s processing centers are signaling things like this is beautiful! This is true! This is good! This is ideal! This is optimal!

The very fact that you can process the ad in a fluent way means the ad is effective. Cognitive fluency equals conversion optimization effectiveness.

Here’s an e-commerce page inviting me to purchase some bottled water that allegedly melted off of a glacier in Norway. I look at this, and it communicates with cognitive fluency.

I know what I’m looking at, what to do, where to click, and how to achieve the desired objective. Conversion is just a click away. Cognitively fluency makes it easy to convert!

The application of cognitive fluency in conversion optimization is remarkably simple: The easier it is for a user to understand and do something, the more likely the user is to convert.

Design for the mind, not just for the eye.

Conversion optimizers are like web designers for the mind. Our goal is to approach a website, a landing page, a form field, a CTA, a conversion funnel with cognitive design in mind.

Web designers are interested in how the user’s eye travels on a page — white space, kerning, type size, color choice. Each of those elements (plus 1.5 million others) are doubtlessly an integral part of conversion optimization.

But the competent conversion optimizer realizes that there’s more to it than that. The visual elements of a page possess remarkable cognitive corollaries.

In order to get from the eye to the mind — where conversion optimization releases its undeniable power — the page must possess cognitive fluency.

As you approach each web page for conversion, keep this idea in mind. You are designing for the mind.


I’m as eager for tactics as the next guy, but cognitive fluency lends itself more to methodological approaches rather than ruthless tactics.

Simply knowing that certain principles about the mind are true helps us develop a more strategic approach to optimizing for conversions.

By understanding the concept of cognitive fluency, you can improve your conversion game.


Jeremy Smith

Digital marketer with a penchant for dance; helping clients see the light through the jungle of tweets since before Twitter was cool.