Cognitive flexibility (switching) and control (inhibition) are among widely accepted cognitive advantages of bilingualism. Switch Cost (SC), i.e., the time difference to complete a switch versus non-switch task, is a construct for measuring the switching ability. The need to control the interference and switching between one's languages leads to recruitment of new brain structures, such as the dorsolateral prefrontal cortex (DLPFC), which in turn decreases SCs. However, this benefit is not equally shared by bilinguals even after considering factors such as age of acquisition (AoA) and proficiency level. A less studied factor could be the language distance (LD) defined as the overall similarity or difference between two languages. As two languages' similarity increases their interference level increases. It is expected that extra accommodations required for handling proximal languages make them more accessible for these bilinguals compared to those with distal languages. Given the brain's inherent limitation in processing ability, a Multi-Switching task could be used to assess bilinguals' information-processing abilities, such as their task-switching ability, in relation to LDs. The current multiple single-subject study used the Color-Word Interference Test (CWIT) and a combined CWIT/color-cued language switching task to compare the switching costs of two groups of bilinguals (N = 10) with shorter (proximal) and longer (distal) linguistic distances, i.e., Spanish-English and Mandarin-English. The results showed a marginal change in the SC level across conditions only for the Spanish-English group. It also showed a moderately lower SC for proximal group compared to the distal group during the multitasking condition. This provides some supports the theory that LD can make a further difference between the cognitive functioning of bilinguals, namely their switching ability. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]