Multitasking is pervasive. With technological advancements, the desire, ability, and often necessity to engage in multiple activities concurrently are paramount. Although multitasking refers to the simultaneous execution of multiple tasks, most activities that require active attention cannot actually be done simultaneously. Therefore, multitasking is often a matter of perception. Unlike previous literature, I study how the exact same activity can be perceived as multitasking or single-tasking. This work is important because many activities in our lives can be perceived as multitasking or single-tasking and this has implications for performance and engagement. The first chapter of this dissertation demonstrates the malleability of people’s multitasking perceptions. That is, I explore different factors that make individuals perceive the same activity as multitasking or single-tasking. In seven studies, I identify different ways of separating an activity into its components to make people feel like they are multitasking. The second, focal chapter of this dissertation explores how the mere perception of multitasking impacts performance across many domains. Across 29 studies (N = 7,880), I find that the perception of multitasking improves performance compared to the perception of single-tasking, holding the activity constant. The third chapter of this dissertation identifies the mechanism underlying this effect, engagement, using a physiological measure of engagement. In seven studies, I show this increase in engagement is a result of the perceived difficulty of multitasking and rule out rival accounts. The fourth chapter presents an internal meta-analysis in addition to examining key moderators. I conclude with implications and next steps.