Time-of-day effects in icon usability

• Main Author: Tyrer, Victoria
• Published: Swansea University 2003
• Subjects: 150.724
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.639281

To date there appears to have been only one study that has examined time-of-day effects in icon interpretation. McFadden and Tepas (1997) found the time taken to respond to iconic stimuli to vary according to the time-of-day and found the exact time-of- day trend to vary according to the memory load involved in the task. This study was replicated, using slightly modified stimuli, and similar findings were obtained to McFadden and Tepas' earlier study. A series of experiments subsequently examined the effects that different icon characteristics and other changes in task demands had on the observed time-of-day trends. The first of this series, compared icons that were made up of a series of features (multi-feature) with those that were relatively wholistic (gestalts). Gestalt icons were found to markedly improve usability by dramatically reducing response times. Additionally, a trend was noted for the exact timing of peak performance to vary slightly according to icon type, with the multi-feature icons showing a slightly earlier peak in performance. The experiments that followed used icons that had been varied orthogonally in terms of their complexity and concreteness and examined other variations in task demands in terms of the semantic memory component required, the visual memory component involved, the difficulty of response required and the difficulty of icon discrimination. Results suggested that icon tasks requiring semantic memory were not susceptible to time-of-day effects. Similarly, neither differences in icon discrimination nor visual memory were critical in determining the diurnal trend observed. Surprisingly, it was difficulty of response that appeared to be a critical factor in consideration of the influence of exact task demands in icon search tasks. Interestingly however, it appeared that abstract, rather than concrete, icons may show more pronounced diurnal performance trends. It was proposed that the effects of different task demands on the observed timeof- day trends exerted their effects through their influence on working memory load, with higher memory load tasks showing an earlier performance peak relative to lower memory load tasks. A framework was proposed for the understanding, and development of, these time-of-day effects in icon usability.