User immersion in computing happens not only in entertainment, gaming, and virtual reality but whenever users are "in the flow", completing their work and communication without thought to the technology that is making it possible. When a user is in the flow, and poor performance brings attention back to the technology, the user is pulled from that immersive experience to focus on computer performance in a negative way. System response time (SRT) is the amount of time that elapses from when a user submits a request until the result is returned from an interactive computing device. Empirical and theoretical literature has repeatedly demonstrated that SRT is a key factor that can dramatically affect user satisfaction. Although it has been suggested that SRT issues would become obsolete with the technological advancements in hardware and software, the amount of literature in this field and its effect on user experience (UX) is a clear reminder that SRT continues to be problematic. Specifically, there is a lack of comprehensive metrics that quantitatively correlates user satisfaction to SRT. This paper will discuss SRT and its influence on user-perceived performance. It will describe how the concept of flow is an essential factor influencing user satisfaction, especially with highly interactive devices. In addition, it will explore how time perception, attention, and feedback can impact users' perception of flow. It describes why the little things (seemingly small or short-duration characteristics of the experience) have the most impact on users' perception of flow. Finally, a new framework for categorizing and mapping UX and SRT's will be presented along with the three guiding principles that dictate this relationship. This new framework provides a systematic approach to enable the objective measurement of flow, and hence, a new user-centric approach to computer performance evaluation. (C) 2015 The Authors. Published by Elsevier B.V.
