Usability Study of Button Size and Spacing in Virtual Reality On-Demand Audiovisual Media Preview Interfaces

Abstract In virtual reality (VR) interface design, button size, and spacing are key design elements. This study investigated these two factors in the context of Fitts' Law within a VR on-demand media preview two-dimensional (2D) interface, assessing both objective performance and subjective perceptions. A convenience sample of 72 participants completed a 2 (large, small button size) × 3 (small, medium, large button spacing) between-subjects factorial experiment. The collected data were analyzed using a two-factor analysis of variance (ANOVA). The results indicated that: (1) small spacing demonstrated shorter task completion times, consistent with Fitts' Law; (2) the button size across all tasks and the spacing used in the sequential clicking tasks showed no significant effects, suggesting that large buttons may lead to inconsistencies with Fitts' Law due to target size saturation, target utilization (uneven distributions of movement endpoints), and task specifications; (3) medium spacing resulted in higher subjective preference perception than small spacing; (4) combinations of small spacing with small size and medium or large spacing with large sizes, received the highest preference perception; and (5) perceived NASA-RTLX workload was higher for large spacing than for medium and small spacing, consistent with Fitts' Law. This study identifies where Fitts' Law holds and where it breaks down or saturates for large 2D media preview buttons in VR, informing improvements in interface usability.