Jakob's Law

Key Points

• •Users transfer expectations they have built around one familiar product to another that appears similar
• •Mental models are internal representations of how systems work, built from cumulative experience across all products
• •By leveraging existing mental models, we create superior UX where users focus on tasks rather than learning new models
• •Fighting conventions forces users to relearn, increasing cognitive load and friction
• •When making changes, minimize mental model mismatch by letting users continue using a familiar version temporarily
• •Familiarity helps users know immediately how to use a product—from navigation to layout to visual cues
• •The less mental energy spent learning an interface, the more users can dedicate to achieving their objectives
• •Snapchat's 2018 redesign failed by launching major changes without gradual iteration—users migrated to Instagram
• •Google succeeds by letting users opt-in to redesigns (YouTube 2017, Gmail, Calendar)—preview, submit feedback, revert if needed
• •[FIGURE 1-1 — Form controls origin] Shows: Side-by-side comparison of physical control panel (toggles, knobs, buttons) and digital form elements (toggles, radio buttons, checkboxes). Teaches: Digital UI elements inherit mental models from physical counterparts—affordances are clear because they map to real-world controls. Reproduce as: Interactive comparison showing physical control → digital equivalent with shared affordance.
• •[FIGURE 1-2 — YouTube 2017 redesign] Shows: Before/after screenshots of YouTube desktop interface transitioning to Material Design. Teaches: Google mitigated mental model mismatch by letting users preview, provide feedback, and revert—gradual adoption reduces friction. Reproduce as: Slider or toggle showing old vs new design with annotation of what changed.
• •[FIGURE 1-3 — Etsy mental models] Shows: Etsy product listing page with familiar e-commerce patterns (grid layout, filters, cart, search). Teaches: E-commerce sites leverage preexisting mental models so customers focus on purchasing, not learning the interface. Reproduce as: Annotated screenshot highlighting conventional patterns (search placement, cart icon, filter sidebar).
• •[FIGURE 1-4 — Mercedes seat controls] Shows: Car door panel with seat adjustment buttons shaped like a seat silhouette. Teaches: Physical products also use mental model mapping—controls shaped like the thing they control are immediately understood. Reproduce as: Diagram showing seat shape → control shape correspondence.
• •[FIGURE 1-5 — Apple Vision Pro UI] Shows: VisionOS interface with familiar components (windows, sidebars, tabs, search fields) floating in space. Teaches: New technology (spatial computing) succeeds by building on existing mental models—windows, tabs, and search work as users expect. Reproduce as: Annotated mockup showing familiar UI patterns in spatial context.
• •[FIGURE 1-6 — User persona example] Shows: Template of a user persona with photo, name, bio, goals, frustrations, and insights sections. Teaches: Personas help teams understand users' preexisting mental models and design accordingly—grounded in real user research. Reproduce as: Interactive persona template with fillable sections.

Guidelines

• ✓Begin with common patterns and conventions; depart only when it makes sense
• ✓Place navigation where users expect it (top, left sidebar)
• ✓Use standard icons for common actions (hamburger = menu, magnifying glass = search)
• ✓Follow platform conventions for mobile (tab bars) vs. desktop (sidebars)
• ✓If you must deviate from convention, provide strong affordances and test rigorously
• ✓When launching redesigns, let users opt-in and revert—don't force sudden changes
• ✓Use design systems and established patterns as your starting point
• ✓Study competitor and category-leader interfaces to understand user expectations
• ✓Use personas, journey maps, and empathy maps to understand users' preexisting mental models

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