How Cognitive Fluency Affects Decision Making

Decision Architecture

Designing for decision making

A column by Colleen Roller
July 4, 2011
  • Why should fancy restaurants print their menus in a font that is elegant, but difficult to read?
  • Why should scary rides in amusement parks have names that are difficult to pronounce?
  • How do people assess the risk of food additives in everyday grocery items?

… And what does any of this have to do with UX design and usability?

Every day, your users make judgments and decisions about the products and services you provide based on the way you present them. In this column, I’ll talk about why seemingly insignificant aspects of information presentation can have surprising effects on people’s perceptions and behavior.

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Cognitive Fluency

In previous columns, I’ve talked about how sensitive people are to the work of decision making. Even though it may be at a subconscious level, people are affected by how easy or difficult it is to think about something. Not surprisingly, it turns out that people prefer things that are easy to think about rather than things that are difficult to think about. This feeling of ease or difficulty is known as cognitive fluency. Cognitive fluency refers to the subjective experience of the ease or difficulty of completing a mental task. It refers not to the mental process itself, but rather the feeling people associate with the process.

Fluency is important because of its power and influence over how we think about things and exerts its power in primarily two ways: its subtlety and its pervasiveness. Fluency guides our thinking in situations where we have no idea that it is at work, and it affects us in any situation where we weigh information. The full force of its power comes from the fact that we often misattribute the sensation of ease or difficulty in thinking about something to the thing itself.


To learn more about how fluency works, let’s start by looking at some research in this area. Some of the earliest research occurred in the 1960s, when Robert Zajonc conducted a series of experiments in which he found that the more people were exposed to certain words, patterns, or images of faces, the more they liked them. Zajonc’s experiments uncovered what we now know as the Mere Exposure Effect—the finding that the number of times people are exposed to certain stimuli positively influences their preferences for those stimuli.

This is an interesting finding because, along with more recent research, it reveals that the feeling of familiarity has a strong influence over what types of things people find attractive. In another series of studies, researchers found that, when they asked people to choose the most appealing face in a group of faces, people tended to select those that were composites of all the others. Psychologists call this the Beauty-in-Averageness Effect.

This research reveals that familiarity is a strong motivator of human behavior. In general, people like things that are familiar because they don’t require as much mental work as things that are new and different do. Familiarity is attractive because familiar things require only limited cognitive resources and feel easy.

The Familiarity / Fluency Link

Because familiarity enables easy mental processing, it feels fluent. So people often equate the feeling of fluency with familiarity. That is, people often infer familiarity when a stimulus feels easy to process. Thus, fluency becomes a common mental shortcut that people use to quickly determine whether a particular stimulus is something they’ve encountered before. Most of the time, this shortcut works well. We don’t need to expend time and mental effort scrutinizing something anew if we’ve already made this mental effort when we previously encountered it.

Sometimes, however, this mental shortcut can lead us astray—especially because there are many things that influence the feeling of fluency. Let’s look at some research that reveals some subtle aspects of information display that influence cognitive processing.

In one study, researchers presented participants with the names of hypothetical food additives and asked them to judge how harmful they might be. People perceived additives with names that were hard to pronounce as being more harmful than those with names that were easier to pronounce. On a subconscious level, people were equating ease or difficulty of pronunciation with an assumption about familiarity. When the pronunciation seemed easy, people assumed it was because they’d previously encountered the additive and had already done the mental work of processing information about it. Since it seemed familiar, they assumed it was safe.

The opposite was true of additives that were difficult to pronounce. The disfluency of a name’s harder pronunciation made an additive seem more foreign, and therefore, worthy of a more wary approach. These findings show that even ease of pronunciation, an aspect of cognitive fluency, by itself can influence perceptions of risk. [1]

Fonts and Cognitive Fluency

Ease of pronunciation is just one of many aspects of cognitive fluency. In a different study, researchers asked participants to read instructions on how to do an exercise routine. As Figure 1 shows, they presented the instructions in two different fonts—a font that was easy to read and a font that was more difficult to read.

When they asked participants to estimate how long it would take to actually perform the exercise routine, people anticipated that it would take almost twice as long to do the exercise when reading instructions in the font that was difficult to read, in comparison to the font that was easier to read. In the first example, people estimated it would take about 8 minutes to perform the exercise, while in the second example, they estimated it would take about 15 minutes. With the font that was easy to read, they also assumed that the exercise routine would flow more naturally and were, therefore, more willing to incorporate it into their daily activities. [1]

Figure 1—Exercise instructions in two different fonts
Exercise instructions in two different fonts

In this study, people were actually transferring the difficulty of reading the instructions onto the task itself! This demonstrates the power of fluency and how it can affect people’s judgment and motivation regarding the adoption of new behaviors. If you want people to adopt new behaviors or perceive something new as being easy, it’s important to consider how the information about it appears in print.

In another study, researchers asked people to choose between two phones. They presented information about the phones in either a font that was easy to read or a font that was more difficult to read. Researchers found that the type of font affected people’s willingness to make a decision. While only 17% of the participants postponed the decision when they received information in the font that was easy to read, 41% did so when the font was difficult to read. Subconsciously, people attributed the difficulty of reading the information as a cue that the decision itself was difficult to make. [2]

Cognitive Fluency and Truth

The readability of fonts can also affect people’s perception of truth. In one study, researchers asked people to view unfamiliar statements in either light-colored print or darker-colored print. Because the print-to-background contrast was better with the darker print, resulting in better readability, people tended to rate those statements as more truthful. [3]

The darker print with better contrast resulted in more fluent mental processing. Because those statements seemed easy to decipher, people subconsciously assumed they were familiar. Because people aren’t good at tracking how many times they’ve heard something, they often mistake familiarity with the number of times they’ve actually heard something. They assume that a statement must be popular—and, therefore, true. Although there are a number of steps in this mental process, they all happen subconsciously and instantaneously, at a Gut level.

From a UX design perspective, it’s important to be aware of the significant impact the visual display of information can have. People’s perception of truth plays a critical role in how seriously they’ll consider your product and service offerings, and ultimately, in their decision outcomes.

Cognitive Fluency and Decision Strategies

We’ve seen how fluency influences perception and judgment. Fluency can also affect which decision strategies people use. In my previous columns, I’ve described how we are of two minds when making decisions—Gut versus Head. Gut makes decisions quickly and effortlessly, while Head is more analytical and systematic.

Researchers have found that, when a stimulus feels fluent, people are more likely to make judgments and decisions based on their first, Gut reaction. However, when a stimulus feels disfluent, people are more likely to reconsider their initial Gut reaction. Disfluency functions as a cognitive alarm that gets people to slow down and reassess a situation.

From a UX-design standpoint, sometimes it’s good to get people to slow down and pay attention—and one way to do this is to deliberately make the information harder to process mentally by making its font harder to read or by using wording that is uncommon or unfamiliar.

The Work of Decision Making

I’ve talked about how people are sensitive to the work of decision making in previous columns. Fluency is key in people’s assessment of work. One intriguing study examined the impact of fluency on students’ self-confidence prior to taking an exam. Researchers split students into two groups and asked one group to think of a few reasons they would succeed in doing well. They asked the other group to think of many reasons they would do well. [4] Which group do you think was more confident that they would do well?

Although it may seem counterintuitive, the students asked to provide only a few reasons for their success ended up being more confident. Why would this be? Why wouldn’t a list of more reasons have a more convincing effect? Researchers concluded that, subconsciously, students were more attuned to the mental work of generating many reasons rather than becoming convinced by the number of reasons they generated.

It is difficult, after all, to think of many reasons for just about anything—and people’s perception about the amount of work that is associated with a task informs their feelings about the object or subject of focus. Thus, researchers concluded that thinking of twelve ways to fail—a hard task—had an equivalent effect to thinking of three ways to succeed—an easier task.

This research is important because the generation of reasons is often integral to decision making. In a subsequent research study, researchers asked people to think of either many or only a few reasons why they would purchase a specific item among a choice set. When they were asked to think of more reasons for their choice, they tended either to defer the decision or to choose the middle option—a decision strategy I talked about in a previous column.

Implications for UX Design

Cognitive fluency—or disfluency—plays a subtle, yet influential role in judgment and decision making. Research has shown that many aspects of design can impact fluency, or the feeling of mental effort—including the style and size of fonts, figure-to-ground contrast, wording and terminology, pronunciation, and others. In general, anything that affects the feeling of the ease or difficulty of mental processing can—and does—affect people’s judgments and decisions.

As I stated earlier, fluency gains its power in primarily two ways: through its subtlety and its pervasiveness. Fluency is at work any time we are in a situation where we weigh information. Its impact on choice and decision making is just as influential as that of other, more tangible aspects of a decision-making context that I’ve mentioned in previous columns—including the number of choices, the types of choices, the effect of difficult tradeoffs, and others. Since fluency, by itself, has just as much influence on choice behavior as these other, more tangible components of a decision environment, it is a critical aspect of designing for decision making. 


[1] Song, Hyunjin, and Norbert Schwarz. “If It’s Hard to Read, It’s Hard to Do: Processing Fluency Affects Effort Prediction and Motivation.”PDF Psychological Science, Volume 19, 2008. Retrieved June 12, 2011.

[2] Novemsky, Nathan, Ravi Dhar, Norbert Schartz, and Itamar Simonson. “Preference Fluency in Choice.” Journal of Marketing Research, August 2007. Retrieved June 12, 2011.

[3] Reber, Rolf, and Norbert Schwarz. “Effects of Perceptual Fluency on Judgments of Truth.” Consciousness and Cognition, Volume 8, September 1999. Retrieved June 12, 2011.

[4] Sanna, Lawrence, and Norbert Schwarz. “Integrating Temporal Biases: The Interplay of Focal Thoughts and Accessibility Experiences.”PDF Psychological Science, Volume 15, 2004. Retrieved June 12, 2011.

Independent Consultant

Boston, Massachusetts, USA

Colleen RollerColleen is a skilled writer and an experienced UX researcher who has spent hours watching people use Web sites and other digital tools. She has a deep understanding of what works—and what doesn’t—from a design and content perspective. Whether it’s an online user interface or the written word, she collaborates with her clients and partners to craft solutions that communicate clearly and succinctly. Colleen always welcomes opportunities to use her writing and UX design and research skills.  Read More

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