Effects of Working Memory Capacity on Workload and Task Performance

Abstract

Working memory capacity (WMC) is generally referred to as a quantitative measure of the ability to maintain relevant information while performing unrelated tasks (Delaney & Sahakyan, 2007). Studies have shown that WMC can vary by individual, with high WMC individuals generally exhibiting better performance on attentional tasks than low WMC individuals. Current research is inconclusive as to how an individual’s WMC affects performance on tasks of varying workload. Kane, Poole, Tuholski, & Engle (2006) tested the relationship between WMC and executive attentional control and found no relationship between individual differences in WMC and performance on basic visual search tasks. Other studies, however, have found that loading working memory interferes with search (Peterson, Beck, & Wong, 2008; Han & Kim, 2004). This dissertation determined if low- and high-WMC individuals perform differently when engaged in complex tasks that tax attentional control and limit automatic forms of information processing, specifically on visual search and navigational driving. The first study tested whether there is a relationship between WMC and visual search performance on visual search tasks that are more complex than the ones used in Kane and colleagues’ 2006 study. The second study explored this relationship in the context of a dynamic driving environment, which has not previously been examined in depth. An attentional battery measuring WMC, selective attention, and other related measures such as visuo-spatial ability was given to each participant in both studies to assess perceptual and cognitive differences. The results of the battery were compared to performance on tasks in both studies. The results showed that WMC did not directly impact primary performance in either of the studies, but differences were found in the secondary loading tasks. In each study, high-WMC individuals responded faster than low-WMC individuals to the loading task. Though their performance was equivalent in the primary task, the two studies presented showed that there were attentional control differences between low- and high-WMC individuals in their ability to multitask. As in the visual search studies of Kane and colleagues (2006) and driving studies of Radeborg and Hedman (1999), low- and high-WMC individuals demonstrated equivalent performance. The implications of this dissertation are useful for understanding tasks that require effortful control. For example, differences between low- and high-WMC individuals may not be apparent under safe driving conditions, but could manifest in decreased response times to hazards on the road when drivers interact with additional tasks created by in-vehicle technologies.