Sources of Secondary Task Interference with Driving: Executive Processes or Verbal and Visuospatial Rehearsal Processes?

We investigated the effects of secondary working memory tasks that loaded either visuospatial working memory or verbal working memory (phonological loop) and which required either rehearsal or executive processes involving stimulus manipulation. The effects of the secondary tasks on driver lookout behavior and driving performance were assessed. Preliminary studies were conducted to select tasks that resulted in similar levels

of accuracy and perceived difficulty across modalities (visuospatial, verbal, rehearse, and manipulate). Piloting and the preliminary studies were also used to evaluate different visual tasks and to select a visual task that could not be encoded verbally. Results of the study reveal that driving performance is significantly impaired while performing a secondary manipulation task than performing a rehearsal task of equivalent difficulty. The study finds that visuospatial and verbal secondary tasks produce the same level of interference with overall driving performance.