Effects of time-of-day on interpreting signs and icons

The effect of time-of-day on performance in a wide range of cognitive tasks has been well documented. Typically performance improves over the morning followed by a dip in performance early in the afternoon. The practical implications of time-of-day effects are apparent in studies which point out the link between post-lunch performance and the increase in car accidents in the early afternoon. One reason for this may be that drivers are slower to interpret and respond to road signs at these times of day, however, almost nothing is known about the effects of time-of-day on interpreting signs and icons. The evidence to date suggests that variations in performance across the day depend upon a combination of factors including the type of icons presented and task demands. A framework is proposed for understanding these effects and the practical implications of these findings are discussed.