What is Ineffective Keystrokes

In usability research it is a common practice to take young and healthy university students as participants for usability evaluations. This chapter focuses on the “weaker” mobile phone users, which have been mostly disregarded in this field: Learning-disabled children. Their interaction with mobile phones is compared to that of average children and students. Results show that the consideration of the “ergonomic worst case,” which means a user group with cognitive deficiencies, leads to qualitatively and quantitatively different insights into the impact of specific design decisions. In contrast, when only students are involved as participants in the evaluation of technical devices, the impact of characteristics of the user interface on the ease of use is dramatically underestimated. One factor hampering the ability of learning-disabled children to interact meaningfully with a technical device may be their big difficulty building a correct mental representation of it. Therefore, this process should be especially supported.