Sound credible

Trust requires logical examination of arguments. However, assessing logic is not neutral—it is influenced by whether we agree with the conclusion. The question is: Do people evaluate an argument's logic objectively, or is their evaluation biased by how desirable they find the conclusion—and what does the evidence tell us?

Studies

The Syllogism Experiment

Evans, Barston, and Pollard presented participants in 1983 with logical conclusions that varied in validity and plausibility. While 97% accepted valid conclusions with plausible results, only 46% accepted valid conclusions with implausible results. Even more striking: 92% accepted invalid conclusions with plausible results. The logical structure was almost completely ignored—what mattered was whether the result "sounded right."

Belief Bias in Advertising Messages

Follow-up studies demonstrated this effect in marketing contexts: Product arguments that confirm existing beliefs are rated as more convincing, regardless of their objective strength. A weak argument that aligns with one's worldview proves more persuasive than a strong argument that contradicts it. For communication, this means connecting to existing beliefs is more effective than arguing against them.

Principle

Which principle for Customer Experience Design can be derived from this? The central principle states: Plausible arguments convince more effectively than logically correct ones, as people evaluate messages primarily on their credibility rather than their logical structure. In customer experience, this means communication and product presentations should align with the target audience's existing beliefs and worldviews rather than challenging them directly. This approach proves particularly effective for complex decisions or emotional topics, where customers seek quick mental shortcuts. However, the principle may be less effective with highly analytical audiences or in domains where expertise commands high trust. The following guidelines demonstrate how to implement this principle in practice.

Guidelines

Building on existing beliefs

Frame arguments to align with your target audience's existing beliefs rather than challenging them. People who say "You're right, and furthermore..." are more persuasive than those who say "You're wrong." Your message must fit within their worldview. The following examples illustrate this guideline:

• Umwelt-Produkte: For the environmentally conscious: 'Protects the environment AND saves money'. For the price-conscious: 'Saves money AND protects the environment as a bonus'. Same facts, adapted framing.

Use customer language

Use the exact words your customers use—not industry jargon or marketing speak. If customers say "cheap," say "cheap," not "budget-friendly." Speaking in authentic customer language signals genuine understanding and builds credibility. The following examples illustrate this guideline:

• Monzo Bank: Instead of 'overdraft facility,' they say 'We'll lend you something.' Banking products in everyday language.

Examples from the Customer World

Illustrate abstract benefits with concrete examples from your target audience's everyday life. A single example in which customers recognize themselves is more convincing than listing ten features. Starting with 'Imagine...' is more powerful than 'Our product can...'. The following examples illustrate this guideline:

• Notion: 'Marie uses Notion to plan her wedding. Tim manages his startup with it.' Real people, real situations instead of feature lists.