Proprioception in the age-related design of handheld devices

Societies around the world are facing the challenges of demographic transitions which bring with them important changes in technology users accompanied by changes in product requirements. It can be expected that national economic performance and quality of life will be determined by the extent to which countries successfully adapt to demographic changes. Much of this adjustment should consider the interaction between older adults and the ever-growing variety of technological systems, whereby mainly handheld devices gained in importance in recent years. As aging brings with it changes in perception, cognition and motor functions, those changes may result in age-related differences in technology usage. The diffusion of handheld devices like smartphones and tablet PCs has changed the nature of interaction with computing systems. This change has proceeded from indirect input, in which the motion of a controller had to be translated to the motion of a pointer on a screen as for example in mouse-driven interaction, to direct input, with touch-based technologies. Hence, the distance of the hand to the screen has changed from being within reach to being in direct contact, as touch technologies are held and controlled by the hands. This difference may have far-reaching consequences as different neuronal streams might be involved depending on the behavioral input. Specifically, the ventral stream is involved in visual identification and recognition (the 'what' pathway), whereas the dorsal stream is involved in processing the spatial location of objects relative to the viewer (the 'where' pathway), which is crucial when touching and manipulating objects. It is hypothesized that developing systems that are adapted to the neurological pathways involved in the interaction could further improve their usage. It is further hypothesized that there are differences in the usage of systems in dependence on subject's age as specific neuronal representations become less accurate with age. This thesis therefore investigates differences in the interactions of adults with handheld devices, based on the ways different age groups interact with these devices. Specifically, device-operation preferences in daily activities are evaluated, and the positions in which the devices are held as users interact with them are studied. Next, proprioception - the sense of one's own body position in space - is analyzed regarding the distance of the hand to the screen in three experimental studies. Results of the experimental studies indicate that the perception of information is more detailed if the stimulus originates near the hands, while at the same time reaction times are faster, and these effects are weaker for older adults. The results of the experimental studies are abstracted to more general design guidelines that can be used for the development and communication of knowledge in order to promote good interface design.