Size matters! How thumbnail number, size, and motion influence mobile video retrieval

Various interfaces for video browsing and retrieval have been proposed that provide improved usability, better retrieval performance, and richer user experience compared to simple result lists that are just sorted by relevance. These browsing interfaces take advantage of the rather large screen estate on desktop and laptop PCs to visualize advanced configurations of thumbnails summarizing the video content. Naturally, the usefulness of such screen-intensive visual browsers can be called into question when applied on small mobile handheld devices, such as smart phones. In this paper, we address the usefulness of thumbnail images for mobile video retrieval interfaces. In particular, we investigate how thumbnail number, size, and motion influence the performance of humans in common recognition tasks. Contrary to widespread believe that screens of handheld devices are unsuited for visualizing multiple (small) thumbnails simultaneously, our study shows that users are quite able to handle and assess multiple small thumbnails at the same time, especially when they show moving images. Our results give suggestions for appropriate video retrieval interface designs on handheld devices.