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Decision Tree Mapping

The Decision Tree Mapping exercise helps transform tacit design knowledge into explicit guidance for complex decision-making. Here's how to implement this exercise effectively:

Purpose:

  • Document the decision-making process behind complex design choices

  • Create reusable frameworks for consistent decision-making

  • Capture expert knowledge that can be shared with the team

  • Transform intuitive design decisions into systematic approaches

Materials Needed:

  • Whiteboard or digital diagramming tool (like Miro, Figma, or Lucidchart)

  • Example design scenarios that required complex decisions

  • Post-it notes or digital equivalents

  • Markers, pens

  • Templates for decision tree structures

Process:

01 Identify Complex Decision Points (30 minutes)

  • Brainstorm scenarios where designers regularly face challenging decisions, such as:

    • When to use different navigation patterns

    • How to select appropriate data visualization types

    • When to use different feedback mechanisms

    • How to handle edge cases in forms

    • Which interaction pattern to use for specific user tasks

02 Select Priority Decision Points (15 minutes)

  • Choose 2-3 high-impact decision points to focus on

  • Prioritize based on:

    • Frequency of the decision

    • Impact on user experience

    • Current inconsistency in approaches

    • Complexity that would benefit from guidance

03 Map Current Decision Process (45 minutes per decision)

  • Start with the core decision question (e.g., "Which navigation pattern should we use?")

  • Identify the key factors that influence this decision

  • Map out the conditional logic as branches:

    • "If [condition], then [decision]"

    • "If mobile context AND many options, then use bottom sheet"

  • Include relevant considerations at each branch point

  • Document the recommended outcome for each path

04 Test with Real Scenarios (30 minutes)

  • Apply the decision tree to past design challenges

  • Verify that following the tree leads to the right decision

  • Refine the tree to address any gaps or inaccuracies

05 Document Rationale (20 minutes)

  • For each major branch point, capture the reasoning behind it

  • Include user-centered justifications

  • Note any research or data supporting the decision path

  • Document exceptions where the rule might not apply

06 Create Final Decision Trees (30-45 minutes)

  • Clean up and formalize the decision trees

  • Create a clear visual hierarchy

  • Use consistent terminology

  • Include examples at terminal nodes

  • Add an introduction explaining when to use this decision tree

Benefits:

  • Makes expert knowledge accessible to junior team members

  • Ensures consistent decision-making across teams

  • Provides rationale behind decisions, not just rules

  • Reduces decision fatigue for common design challenges

  • Creates living documentation that can evolve with new insights

Example Decision Tree Topics:

  • Selecting the appropriate navigation pattern

  • Choosing between modal, slide-out, or inline forms

  • Determining when to use different notification types

  • Selecting appropriate data visualization for different data types

  • Deciding on responsive layout approaches for different content

This exercise is particularly valuable for complex design systems where simple rules aren't sufficient. The resulting decision trees become powerful tools that combine the flexibility of principles with the specificity of guidelines.