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TopIntroduction
Mobile devices are challenging HCI in many new and unexpected ways. Many of these challenges can be seen to stem from two main aspects:
Firstly, mobile devices are becoming powerful and this is allowing increasingly complex software to be used on them. Secondly, mobile devices are being used in far more complex environments.
Examples of these phenomena can be seen, for example, in mobile learning software, where one of the main issues facing the usability of these types of applications was suggested to be cognitive load (Deegan and Rothwell, 2010a). Cognitive Load Theory explains how the human mind interacts with instructional materials for learning and has several guidelines that are used to assist in the design of instructional material used for learning (Sweller et al., 2011). This paper will explain related previous work and present the results of an experiment, the final experiment of the series, which investigates the relationship between Cognitive Load Theory and Mobile HCI. This experiment suggests that there are two different types of distraction which uniquely affect performance and usability separately.
TopLiterature Review
Usability is defined by the ISO as “the effectiveness, efficiency and satisfaction with which specified users can achieve specified goals in particular environments.” (ISO 9241-11, 1998). A usable system should be easy to use (utility) and easy to learn (learnability) (Nielsen, 1994).
In recent years the notion of 'ease of use' has been applied to Usability where the general philosophy is based on making things 'easy' for the user. This approach stemmed from work done by Miller (1956) which determined that human cognitive resources were limited. Miller’s work led, in part, to the development of Cognitive Load Theory.
Cognitive Load is the demand for mental resources associated with processing information in working memory. HCI attempts to reduce the inputs that humans had to process; making things easier (less Cognitive Load) meant making things more effective, efficient and satisfying to use. Research (Sweller et al., 2011, Sweller et al., 1998, Sweller and Chandler, 1994, Sweller, 1998, Paas and Van Merrienboer, 1994) suggests that our Cognitive Load can and will vary depending on the characteristics of the task and those of the user.
Cognitive Load Theory was developed primarily as a theory for learning, specifically to help understand problem solving (Sweller et al., 1998, Sweller, 1998, Bannert, 2002).
Previous research (Deegan and Rothwell, 2010b) suggested that there were many unconsidered extraneous distractions that a mobile user would face and presented a model of these distractions. They suggested that distractions can occur from 1) the content itself 2) the application 3) the system software 4) the device hardware and 5) the greater environment (Figure 1).
Figure 1. Sources of cognitive load
By combining several methods of balancing Cognitive Load (Sweller et al., 2011, Kirschner, 2002, Mayer and Moreno, 2003, Van Merrienboer et al., 2002) instructional designers can ensure that the learner’s Cognitive Load is at the suitable level with regard to the content only. HCI must then consider how to ensure the correct Cognitive Load is portrayed based on the application, system, device and environment.
These new concerns demand that efforts be made to understand how these distractions affect the usability of mobile devices.
TopThe final experiment, presented in this paper, builds on five previous experiments (Deegan and Rothwell, 2011, Deegan 2013a, Deegan 2013b, Deegan 2013c) and attempts to find an observable link between cognition, distraction, usability and performance. Below are brief summaries of the previous related work.