Dynamics of Viewer's Attention: Making Content More Engaging in a Vertical Frame

The proliferation of mobile-first social media platforms has established vertical video (9:16 aspect ratio) as a dominant format for content consumption. However, established principles of visual composition, largely derived from landscape cinematography, may not directly apply to this narrow, portrait-oriented frame. This study investigates the impact of subject positioning on viewer attention within vertical videos. Using mobile camera-based eye-tracking technology provided by RealEye.io, we conducted a within-subjects experiment with 40 participants. Each participant viewed two purpose-created, 20-second stimulus videos. The first video (Dynamic AOI) featured the primary Area of Interest (AOI) in multiple, varied locations throughout the frame. The second video (Central AOI) consistently positioned the AOI in the central third of the frame. Key eye-tracking metrics were analyzed, including fixation duration, saccade count, and a derived attention efficiency metric, Coefficient K (ratio of fixations to saccades). The results revealed a statistically significant difference between the two conditions. The Central AOI video elicited significantly longer average fixation durations and fewer saccades compared to the Dynamic AOI video. Consequently, Coefficient K was substantially higher for the centrally framed content. These findings suggest that central framing in vertical video reduces cognitive load, minimizes visual search behavior, and facilitates more sustained and focused attention on the primary subject. The study concludes that for content creators, marketers, and platform designers seeking to maximize viewer engagement and message retention in the vertical video ecosystem, a deliberate strategy of centering the primary subject is demonstrably more effective