Abstract
In this experiment, older and younger novice mobile phone users were examined when using handsets of different complexity. The independent variables were user age (young: 20 – 35 years; old: 50 – 64 years) and cognitive complexity of two mobile phones (Nokia 3210; Siemens C35i). The cognitive complexity of the phones was defined by the number of production rules applied when processing the four experimental tasks. Dependent variables were effectiveness and efficiency as taken from user protocols and the reported ease of use. The less complex phone (Nokia) performed significantly better than the complex one (Siemens). However, the benefit from the lower complexity was much larger than theoretically predicted. Thus, defining cognitive complexity of technical devices by the number of production rules does not account for the real difficulties which users experience. Older users had a lower navigation performance than younger users, however their performance matched younger users' when using mobiles with low complexity.
Acknowledgements
The authors express their gratitude to the patience, especially that of the older users, of those taking part in the study and overcoming the resentments of being ‘tested’. Thanks also to René Mueller, Julia Pollmann and Volker Pinsdorf for their research support and to Philipp Brauner who developed the experimental software. A final thank you is devoted to Julie Williamson and Sarah Hatfield as well as to two anonymous reviewers and Ahmed Çakir for helpful and constructive comments about an earlier version of this manuscript.