Prior experience in the use of domestic product interfaces

Interaction design and usability has focussed on instantaneous interaction, but the effects of prior experience are evidently important. Extant theories debate the nature of mental models or knowledge structures and their content, but less emphasis has been given to the effects of the various contributors to "unconscious" prior experience and their interaction with capability during real-time use of products. As a first step towards understanding product learning for inclusive design, this paper examines the role of prior experience, age and cognitive capability in individuals' performance with daily living products. Two microwave ovens were tested that had the same underlying functionality, but with the interface variations of dial or button control. The differences in performance were such that dials were found to be easier to use for both younger users and also those with higher cognitive ability. This was not related to prior experience as measured in a product knowledge questionnaire. However, it was possible that users possessed some degree of prior experience with specific interface elements and their use. Hence, in a second training-transfer experiment with DAB radios, participants were trained to a criterion of low error with a common base product to investigate the performance impact that subsequently resulted from switching to two further interfaces that varied in known interface properties. Transfer gave rise to a significant increase in time to complete set tasks proportional to the degree of difference. Small variations of interface function and appearance led to specific time-consuming misperceptions and trial-and-error exploration of interface functionality. Detailed error analysis further suggested the misapplication of specific sequences learnt with the original training. Both studies clearly indicate a general reduction of performance with increasing age and with reduced cognitive capability, but they also suggest that users were able to learn new interface sequences more effectively when they possessed higher cognitive capability. The results were not consistent with an interpretation in which knowledge-based mental models of the underlying functions of daily living products were dominating interaction effectiveness. They are, however, consistent with accounts of interaction that propose that in the absence of an adequate previously acquired mental model, users primarily resort to the application of skill-based or rule-based schemas to achieve task goals with everyday products (Freudenthal in Learning to use interactive devices: age differences in the reasoning process. Eindhoven University of Technology, Eindhoven, 1998; Blackler in Intuitive interaction with complex artefacts. Queensland University of Technology, Brisbane, 2006; Langdon et al. in Univers. Access Inf. Soc., 6(2): 179-191, 2007).