  The increasing number of users with multiple mobile devices underscores the
importance of understanding how users interact, often simultaneously, with
these multiple devices. However, most device based monitoring studies have
focused only on a single device type. In contrast, we study the multidevice
usage of a US-based panel through device based monitoring on panelist's
smartphone and tablet devices. We present a broad range of results from
characterizing individual multidevice sessions to estimating device usage
substitution. For example, we find that for panelists, 50% of all device
interaction time can be considered multidevice usage.

Human-Computer Interaction