Where scrollbars are clicked, and why

Area of Science:

• Human-Computer Interaction
• Cognitive Psychology
• Usability Studies

Background:

• Scrolling is a fundamental interaction method for navigating visual displays.
• Understanding user scrolling behavior can reveal inefficiencies and infer user intent.
• Current models may not fully capture the nuances of scrollbar interaction.

Purpose of the Study:

• To investigate how users position clicks on a scrollbar based on their intended scrolling action.
• To determine the factors influencing scrollbar click-position selection.
• To compare user scrollbar interaction with physical device manipulation heuristics.

Main Methods:

• Conducted two online experiments to systematically record scrollbar click positions.
• Analyzed click positions in relation to intended scrolling actions and contextual factors.
• Evaluated potential explanations for click-position selection, including cursor distance, memory load, and motor-cognitive factors.

Main Results:

• Scrollbar click positions were not solely optimized for cursor travel distance or cognitive load.
• Click positions varied significantly based on the immediate context and prior scrolling actions.
• Observed user behavior aligns with simple heuristics used in planning movements for physical devices.

Conclusions:

• User scrollbar interaction follows context-dependent heuristics, not just optimization principles.
• This behavior resembles physical device manipulation, suggesting a unified movement planning approach.
• Findings can enhance human-computer interaction models and improve prediction of user behavior during scrolling.