Human-Computer Interaction (HCI) is “the study of how people communicate and interact with computer systems and how to design, build, and evaluate technologies to facilitate those interactions” [Inkpen, 1997]. HCI is a complex and highly interdisciplinary area of research. The main contributing disciplines include Computer Science, Cognitive Psychology, Social and Organizational Psychology, Ergonomics and Human Factors.
Usability is a central concept in HCI. It is defined in ISO 9241-11 as “the extent to which a product can be used by specified users to achieve specified goals with effectiveness, efficiency and satisfaction in a specified context of use”. Nielsen [1993] describes five characteristics of usability:
• Ease of learning: the interface should be designed to allow users who have never seen it before to learn to use it quickly to succeed in accomplishing basic tasks.
• Efficiency of use: the interface should be designed to allow rapid accomplishment of tasks for more experienced users.
• Memorability: the interface should be easy to remember, so that the casual user is able to return to the system after some period of not having used it, without having to learn everything all over again.
• Error frequency and severity: the interface should be designed to minimize the number and severity of errors, and allow for quick error recovery.
• Subjective satisfaction: the interface should be pleasant to use, so that users are subjectively satisfied when using it.
Because the purpose educational software is not just task performance but rather the promotion of learning, its usability is not related directly to the efficiency and effectiveness of the task execution, but to the effectiveness and efficiency of learning that should occur during this activity. Researchers have developed some guidelines with respect to the usability of educational software in order to help designers produce more usable systems [Sharples and Beale, 2002; Squires and Preece, 1999]. Barker and King [1993] provide some factors which their research suggests are of key importance to successful educational software. These factors include: quality of end-user interface, engagement, interactivity, tailorability, appropriateness of multimedia mix, mode and style of interaction, quality of interaction, user learning styles, adequacy of ancillary learning support tools and suitability for single user/group/distributed use. Mayes and Fowler [1999] also discuss some general design issues related to usability in three general kinds of educational software. However, the interface design of educational software is an extremely complex topic that goes beyond the usability during task performance because of the need to allow and support learning. Thus, general usability criteria and guidelines that are useful, remain quite limited. In order to examine usability that fulfils learning purposes, a wide range of methods should be used in the evaluation. Dimitracopoulou [2001] states that the usability evaluation of educational software should provide information with significant interpretative value, and should be applied not only during the whole development lifecycle but also during the postproduction period. Dimitracopoulou suggests that repeated informal and formal evaluation methods should be used in laboratory as well as in real school contexts.
User-Centered Design (UCD) is a widely accepted HCI methodology for designing usable applications. UCD focuses on the needs of the user and meeting those needs in the interface [Norman and Draper, 1986]. It offers a collection of tools and methods for planning, iterative development and evaluation, and fosters a tight evaluation feedback loop to assure that the deficiencies are identified and corrected at an early stage of the development life-cycle [Dimitracopoulou, 2001]. Learner-Centered Design (LCD) offers a new perspective in which HCI interaction principles are combined with educational interaction support [Guzdial et al., 1995]. Because children are becoming an increasing portion of the computer market, it is becoming important to apply Learner-Centered Design theory to more specific topics. As a unique group of learners, children’s needs and interactions are different from those of adults. Inkpen [1997] discusses three aspects of the difference:
• Motor skill development: children’s motor skills are not fully developed. For example, some researchers have found that children have difficulty performing mouse operations that require sustained pressure on the mouse button, thus point-and-click interaction style is better for children than the drag-and-drop interaction style [Inkpen, Booth, and Klawe, 1996; Stromme 94].
• Cognitive differences: children’s cognitive capabilities are different from those of adults. Children may have physical or cognitive difficulty using adult interaction techniques.
• Experiential differences: children have different experiences and perspectives from adults. For example, common adult metaphors in software may not make sense to children. Child-appropriate metaphors should be used in software for children.
In order to make children’s educational software effective, designers should take a child-centered view. Software should be designed in a way that addresses children’s cognitive, affective, and behavioral needs [Sedighian, 1998]. Much of the existing research focuses on conceptual aspects of software, such as how to help children learn particular subject matter, or how to improve their thinking and problem solving skills [e.g., De Corte, Kinn, Mandl and Verschaffel, 1992; Duffy, Lowyck and Jonassen, 1993; Klein, 1985; Forman and Pufall, 1988]. There is little research on how to design effective educational interaction [e.g., Soloway, 1996; Sedighian and Klawe, 1996; Holst, 1996]. More research in this area should be conducted in order for children to be able to use these systems effectively.
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