Law of Similarity

Visual information shapes first impressions and purchase decisions. Intuition suggests that brands should be unique to stand out. However, customers categorize rapidly—what doesn't look familiar gets ignored or mistrusted. The question is: When does similarity harm and when does it help? How do successful brands use the visual codes of their category, and what does the evidence tell us?

Studies

Wertheimer's Dot Pattern Experiment

In 1923, Max Wertheimer described a series of experiments on visual perception in his seminal work "Investigations in Gestalt Theory." In a classic experiment, he showed subjects patterns of dots: first with uniform spacing, then with alternating close and wide spacing, and finally with alternating colors. The surprising result: although the same dots were presented, subjects perceived completely different groupings. With similar spacing, rows emerged; with similar colors, columns appeared—automatically, without conscious effort. The brain constructs relationships based solely on similarity. This effect was so powerful that it could override competing grouping principles.

Category Entry Through Visual Similarity

Byron Sharp and Jenni Romaniuk investigated the role of visual similarity in market entry at the Ehrenberg-Bass Institute in 2016. They analyzed over 200 product launches across various categories and compared success rates. Products that used the established visual codes of their category—in color, shape, and layout—achieved on average 23% higher recognition and 34% higher purchase intent in the first year compared to products with radically different designs. The surprising finding: this effect was stronger for premium products. Those that didn't look like their category had to invest significantly more in explanation and trust-building. The most successful brands used category codes for 70-80% of their visual elements and differentiated themselves in only 20-30%—mostly through a distinctive color or shape.

Principle

Which principle for Customer Experience Design can be derived from this? The Law of Similarity demonstrates that successful customer experience design requires a strategic balance between category conformity and targeted differentiation. Companies should first leverage the established visual codes of their product category—including color schemes, layout structures, and typical design elements—to create immediate orientation and implicit trust. Only on this familiar foundation can targeted differentiating features be deployed that capture attention without jeopardizing category membership. This approach is particularly effective in established markets with clear visual conventions, though it is less relevant in entirely new product categories. The following guidelines show how to implement this principle in practice.

Guidelines

Identify visual codes of the category

Systematically analyze the visual patterns of successful competitors: Which colors dominate? Which shapes, layouts, and typographies are standard? These codes aren't coincidental—they've proven functional. Customers expect them. Use 70-80% of these established codes for quick category recognition, then differentiate yourself in only 20-30% through distinctive brand assets.

Characterize product groups by similarity

Design related products or variants to be deliberately similar: use the same color for a product line, the same shape for related services, or the same icons for a feature group. These visual clusters enable quick navigation and reduce cognitive load. Customers don't need to analyze each element individually—they can recognize patterns at a glance.

Leverage industry standards for trust

In regulated or sensitive industries—finance, healthcare, and insurance—visual standards establish immediate trust. Professional typography, industry-specific color codes (blue for finance, green for sustainability), and clear layouts signal professionalism and competence. Innovation in these sectors is required in service and product delivery, not in design. Companies that deviate radically from visual conventions must work considerably harder to build trust.

Ensure visual consistency across touchpoints

Maintain high visual consistency across all customer touchpoints—website, app, emails, documents, and packaging. This consistency leverages the law of similarity: customers immediately recognize that all elements belong together. It creates coherence, reduces uncertainty, and strengthens brand recall. Inconsistent visual language appears unprofessional and fragments brand perception.