Outline or Solid? The Role of Icon Style on User's Perception

Despite the many studies investigated the impact of icon design on usability in the past, few have compared outline icons with solid icons. This study combines familiarity training, recognition tasks, and visual search tasks to explore how icon design style and internal cognitive characteristics jointly affect visual perception. A total of 120 pairs of solid icons and corresponding outline icons were collected and designed. Subsequently, participants were asked to rate icons based on familiarity and concreteness, excluding those that were either too familiar or too unfamiliar. After 27 participants were familiarized with all of the icons over two training sessions, they were required to complete the task of recalling icons with relevant semantic meanings. Finally, to further decompose the users' visual perception process, participants' ability to visually search for icons was additionally tested. The results indicated that participants performed significantly better at recognizing and visually searching for solid icons, especially when they were unfamiliar. However, the visual perception advantage decreased with an increase in familiarity. In addition, strong evidence was found indicating that concrete solid icons have the highest visual search performance. The findings in this study provide practical guidelines for user interface design.