Introduction
Fitts’s Law, a predictive model for human movement in human-computer interaction, states that the time required to reach a target area is a function of the distance to and size of the target. This principle is foundational in user experience (UX) design, guiding the placement and sizing of interactive elements to enhance usability. This case study explores how SpeedyPay, a digital payment app, applied Fitts’s Law to improve its user experience, resulting in reduced task completion times and higher user satisfaction.
Background
SpeedyPay was known for its fast and secure transactions but struggled with complaints about the usability of key features, such as bill payments, fund transfers, and account management. User feedback identified frustration with:
- Small, hard-to-tap buttons.
- Inconsistent spacing between frequently used elements.
- Poor placement of critical actions, requiring users to navigate extensively.
These issues increased user errors and completion times, leading to decreased user satisfaction and retention.
Challenges
- Target Size and Selection:
Small touch targets on mobile screens led to frequent input errors, especially for users with larger fingers or accessibility needs. - Placement of High-Frequency Actions:
Core actions (e.g., “Pay Now,” “Transfer Funds”) were placed far from the user’s natural thumb reach, slowing interaction on mobile devices. - Navigation Complexity:
Users needed multiple taps and extensive scrolling to access commonly used features, increasing cognitive load and task frustration.
The Fitts’s Law-Driven Redesign
1. Enlarging and Optimizing Touch Targets
- Action:
The design team increased the size of tappable elements, ensuring they met or exceeded the recommended 48×48 pixels for touch interfaces. Buttons for critical actions (e.g., “Confirm Payment”) were made larger and visually distinct.- Secondary actions were smaller but still usable, preventing accidental taps.
Outcome:
Error rates dropped by 35%, and users reported fewer issues with tapping the wrong targets.
2. Thumb Zone Optimization
- Action:
Based on research into thumb zones on mobile devices, the team repositioned frequently used actions (e.g., “Pay Now”) within easy reach of the user’s thumb. Less critical options were moved to the top or bottom corners.- Designed a floating action button (FAB) for universal access to the most-used feature: Quick Payment.
Outcome:
Task completion times improved by 25%, and users praised the app’s intuitive layout.
3. Reducing Distance Between Related Actions
- Action:
By grouping related functions (e.g., “Add Payee” next to “Transfer Funds”), the app minimized the distance users needed to move their fingers. Dropdowns and sliders were also replaced with larger, easily selectable options.
Outcome:
Users experienced smoother workflows, with an average of two fewer taps required per transaction.
4. Incorporating Visual Feedback
- Action:
To further assist users, interactive elements were enhanced with real-time visual feedback, such as button highlighting and animations, signaling successful taps or actions.
Outcome:
This reduced user hesitation and confirmed that inputs were accurately received, boosting confidence in the app.
Results
- Improved Usability Metrics:
Usability testing revealed a 30% decrease in task completion time and a 20% reduction in navigation errors. - Higher User Satisfaction:
Post-redesign surveys showed a 40% increase in user satisfaction scores, with specific praise for the app’s responsiveness and ease of use. - Increased Retention Rates:
User retention improved by 18%, driven by the enhanced experience and reduced frustration. - Business Growth:
SpeedyPay saw a 15% increase in transaction volume, attributed to users spending more time on the app without abandoning tasks.
Conclusion
Fitts’s Law provided a scientific basis for SpeedyPay’s redesign, focusing on target size, placement, and proximity to optimize interaction. The case highlights that effective application of this principle can significantly enhance usability, making apps more intuitive and enjoyable to use. By integrating Fitts’s Law into their design strategy, SpeedyPay not only improved the user experience but also achieved measurable business benefits.
Key Takeaway:
Fitts’s Law is a powerful tool for improving user interfaces, particularly in mobile and web applications where precision and ease of access are critical. Designers must prioritize intuitive placement and sizing of elements to ensure seamless interaction for users.
