Detailed analysis of distraction induced by in-vehicle verbal interactions on visual search performance

We examined the negative effect of in-vehicle verbal interaction on visual search performance. Twenty participants performed a primary visual search task and a secondary verbal interaction task concurrently. We found that visual search performance deteriorated when the secondary task involving memory retrieval and speech production was performed concurrently. Moreover, a detailed analysis of the reaction time as a function of set size revealed that the increased reaction time was attributed not to the slowing of inspecting each item but to the increased processing time other than the inspection of each visual item, possibly due to task switching between the primary visual search task and the secondary verbal task. These findings have implications for providing information from in-vehicle information devices while reducing the risk of driver distraction.