Exploring the Bilingual Advantage in Executive Control: Using Goal Maintenance and Expectancies

Previous research has shown that bilingualism helps to offset age-related losses in certain executive processes such as inhibitory control, task switching and divided attention. The two studies presented in this dissertation investigated possible mechanisms underlying this bilingual advantage in executive control by examining the role of expectancies and goal maintenance in monolingual and bilingual younger (30 to 40 years) and older adults (60 to 80 years). In Chapter 2, the fadeout paradigm (Mayr & Liebscher, 2001) was used to examine differences in the ability to disengage from an irrelevant task cue. Testing began with single task blocks of shape and colour classifications presented separately, followed by a task switching block in which the two tasks alternated randomly. On trial 49, one of the tasks became irrelevant, leaving only a single task to perform. The critical variable was the point at which participants performance reflected this change by examining the number of trials required to return to single task block speed. Results showed that both younger and older bilinguals returned to single task block speeds sooner than monolinguals. The results were interpreted as showing that bilinguals were better able to use task cues to improve task performance and that outsourcing control to task cues may be beneficial. In Chapter 3, a dual modality classification paradigm was used to determine the speed at which two tasks could be executed at the same time as a means of measuring the ability to sustain task goals. The task required participants to simultaneously respond manually to visual stimuli and verbally to auditory stimuli. Results revealed that younger and older bilinguals showed smaller costs in responding to two tasks whereas monolinguals experienced larger delays in making their responses. Proportion analysis of dual task costs and pairs of responses revealed a bilingual advantage and did not show any age-related increases in costs. The results were interpreted as demonstrating the strength in goal maintenance in bilinguals, allowing them to establish a task goal, control interference from stimulus pairings in order to uphold the goal, and to manage multiple streams of information, and these abilities are sustained in aging