The Effects of Working Memory Capacity on Workload and Task

Yi-Fang D. Tsai

Advisor: Matthew S. Peterson, PhD, Department of Psychology

Committee Members: Carryl Baldwin, Aimee Flannery

David J. King Hall, Room 2072
July 22, 2011, 10:30 AM to 07:00 AM


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). Although studies have shown that WMC can vary by individual, there is a shortage of information on how an individual’s working memory capacity ranges across tasks. Previous research has shown task performance benefits for individuals with high working memory capacity, with some exceptions for individuals with low working memory capacity. Kane and colleagues (2006) tested the relationship of WMC and executive attention control and found no relationship with individual differences in WMC and performance on visual search tasks, namely on feature-absence, conjunction, and spatial configuration search tasks. However, other studies have found that loading working memory interferes with search (Peterson, Beck & Wong, 2008; Han & Kim, 2004).

 The goal of this dissertation was to determine if complex tasks aimed at engaging the control of attention and limiting automatic forms of information processing will predict better performance for high WMC individuals compared to low WMC individuals. The first study tested whether the use of a more complex visual search task better demonstrates a relationship between WMC and visual search performance. The second study also explored this relationship in the context of a dynamic driving environment. In addition to crash involvement among older drivers that may be attributed to differences in perceptual and cognitive abilities, studies have suggested a relationship between working memory and performance on concurrent driving tasks that can adversely affect a driver’s situational awareness. An attentional battery was given to each participant to assess perceptual and cognitive differences. The results of the battery were compared to performance on a visual search and secondary number-letter task in the first study and a driving and secondary peripheral detection task performance in the second study.

 While WMC did not directly impact search performance in the first study and driving performance in second study, WMC affected performance on the secondary tasks and the ability to resume tasks. Differences in WMC was found in the secondary loading tasks where high WMC individuals had faster response times compared low WMC individuals, indicative of strain on attentional resources and an increase in workload demand. This demonstrates that low and high WMC individuals can, to at a certain extent, perform equivalently, such as shown in visual search studies like Kane and colleagues (2006) and driving studies like Radeborg and colleagues (1999); however, performance differences are noticeable when given more cognitive load in the form of secondary tasks. The two studies also showed that there were attentional control differences between low and high WMC individuals in their ability to multi-task. The implications of these studies can be considered for operations that require effortful control where the contributions of an individual’s WMC are limited such as with designing for cockpit operation and driving.