Impair readability

Information should be easy to understand—that is the credo of good communication. Clear fonts, simple language, and quick comprehension are considered hallmarks of quality. Yet customers forget details, skim over important information, and make hasty decisions. The question is: Can deliberately impaired readability lead to deeper processing? When does effort in reading make sense—and what does the evidence tell us?

Studies

The Font Experiment

Adam Alter and Daniel Oppenheimer conducted an elegant experiment at Princeton University in 2008. Twenty-eight students read identical text about three fictional alien species—once in easy-to-read 12pt Arial black, and once in hard-to-read 12pt Comic Sans MS 60% gray. Afterward, they answered questions about specific details. The surprising result: the group that read the hard-to-read font recalled 14.45% more correct details than the Arial group. The cognitive effort required for reading had deepened information processing. In a follow-up experiment involving lottery descriptions, researchers found that hard-to-read lottery tickets were perceived as less likely to win—the disfluency triggered more skeptical thinking.

The Classroom Study

In 2011, Daniel Oppenheimer and colleagues tested the disfluency effect in real classrooms with 222 high school students from Ohio. Over several weeks, students received instructional materials in either easily readable standard fonts (Arial, Times New Roman) or harder-to-read variants (Comic Sans MS Italic, Bodoni MT Italic). At the end, all students took the same test. The results: Students who used the harder-to-read materials scored better on regular class tests, averaging 86.5% compared to 72.8%. The effect was particularly strong in complex subjects like physics and chemistry. The impaired readability forced students to read more slowly and process information more deeply—resulting in measurable learning gains.

Principle

Which principle for Customer Experience Design can be derived from this? The Disfluency Effect demonstrates that deliberately reducing readability can be a powerful tool for directing users' attention and promoting deeper processing. For complex product information, important contract terms, or decision aids, slightly reduced readability can encourage customers to think through content more consciously rather than merely skimming it. However, this approach only works with motivated users who are willing to invest additional cognitive effort—when motivation is low or time pressure is high, impaired readability can lead to abandonment. Additionally, the difficulty should be applied subtly, as excessive readability impairment causes frustration and degrades the user experience. The following guidelines show how to implement this principle concretely and responsibly.

Guidelines

Making important disclaimers deliberately difficult

Make Important Disclaimers Deliberately Harder to Read Legally important information—such as risks, side effects, or contract terms—should not be presented in a perfectly readable font. A moderately harder-to-read typeface (for example, slightly smaller text, subtle italics, or medium contrast) forces customers to read more slowly and actually process the information. This approach protects against hasty decisions and increases genuine understanding of important limitations. Important: The information must still be easily decodable—just not skimmable.

Visually slow down complex steps

For multi-step processes requiring careful attention—such as configuration, installation, or contract completion—critical steps should be visually slowed down. Rather than using perfectly organized bullet points, consider employing slightly italicized fonts, reduced contrast, or unconventional yet readable typefaces for important instructions to decrease processing speed. This approach leads to fewer errors and improved retention of crucial details. The effect proves particularly valuable for safety-critical or irreversible decisions.

Design training content to be deliberately more challenging

Onboarding materials, product training, and knowledge databases should not be designed solely for maximum ease of consumption. For content requiring long-term retention, a moderately difficult presentation—such as slightly smaller fonts, reduced contrast, or imperfect spacing—can increase learning depth. Customers who work through mildly challenging materials demonstrate better long-term retention and deeper understanding. This approach is particularly valuable for complex B2B products or software features that require mastery.

Design brand content with maximum fluency

The disfluency effect must be applied selectively. For emotional content, brand messaging, or creative elements, maximum fluency should be the goal. Easily processed information generates positive feelings, familiarity, and affinity—precisely what branding aims to achieve. Claims, hero sections, and emotional narratives perform better in highly readable, aesthetically pleasing fonts. The principle: analytical content benefits from disfluency, while emotional content requires fluency.

Emphasize important elements through contrast

Highlight critical information through visual differences – different font, color, or position. The small friction forces attention. The following examples illustrate this guideline:

• Rechtstexte: Important clauses in red text on a yellow background – unmissable, slightly unpleasant, but effectively read.

Confirmation for critical actions

For irreversible actions, require explicit confirmation. The brief pause prevents mistakes. 'Are you sure?' is sometimes exactly right. The following examples illustrate this guideline:

• Mailchimp: Before sending to 10,000 recipients: 'This cannot be undone. Are you sure?' – protects against accidental clicks.

Summary before completion

Show a complete summary of all decisions before the final step. This friction prevents regret and returns. The following examples illustrate this guideline:

• Autokonfiguratoren: Complete summary of all options and prices before ordering – prevents 'I didn't know that...' later.