Elderly people seem to encounter more problems than people from other age groups do, when using consumer electronics products and their accompanying manuals. This may be due to the absence of some kinds of information. In this study the effects of the absence of different information types in instructions on action performance were explored for different age groups. Younger (aged 20–30 y.) and elderly (aged 60–70 y.) participants installed a VCR with the help of the manual, while working aloud. The absence of goal information, consequence information and identification information in the instructions proved to have a negative effect on task performance, especially for the elderly participants. When one of these information types was missing in the instructions, the elderly performed more actions incorrectly than when the information was stated explicitly.

This article discusses the adequacy of two modes of presenting information on a computer screen, i.e., the alternating screen presentation in which information is presented “screen by screen” and the simultaneous screen presentation that shows different sources of information simultaneously on the same screen. Using a simultaneous or an alternating screen presentation, subjects had to perform short writing tasks, half of which required the use of one on-line document, the other half required two documents. The subjects' task performance as well as their appreciation of the task and the presentation mode were measured. The results show that performance and appreciation data do not run parallel. While all subjects clearly prefer a simultaneous mode of presenting information on the screen, performance data are much more varied and less clear cut: when reading, subjects performed significantly better in the alternating mode; when producing a text, subjects slightly benefited from simultaneous screens.