Effects of Bilingualism and Task Switching on Hemispheric Interaction Suzanne E. Welcome & Christine Chiarello Univ

1. 1 7 1 7 1 3 WithinVF (One Hemisphere Can do Alone) AcrossVF (Hemispheres Must Communicate) No Match p = .010 1 7 7 1 1 3 p = .010 Same Task (less demanding) 3 3 3 7 1 p = .002 1 Percent Error Add Task (more demanding) Effects of Bilingualism and Task Switching on Hemispheric Interaction Suzanne E. Welcome & Christine ChiarelloUniversity of California, Riverside Introduction Methods Task Difference in Across Hemisphere Advantage Differs Between Language Groups • Attentional resources may be managed by the degree of interhemispheric interation. • If a task is attentionally demanding, performance is improved when relevant information is divided across hemispheres; if the task requires less attention, performance is best when relevant information is presented to a single hemisphere (Banich 1998; Weissman & Banich, 2000; Mickels & Reuter-Lorenz, 2004). • Bilingualism might impact interhemispheric interaction. • Bilingualism might result in a more widespread, less left-lateralized cortical network devoted to language. • Several neuroimaging studies have suggested that bilinguals activate right hemisphere regions to a larger extent in one of their languages than another (Perani, Paulesu, Galles, Dupoux, Dehaene, Bettinardi, et al., 1998; Dehaene, Dupoux, Mehler, Cohen, Paulesu, Perani, et al.,1997; Ding, Perry, Peng, Ma, Li, Xu, et al., 2003). • Bilingualism might place demands on general cognitive control mechanisms which are not lateralized. • The flexible use of multiple languages requires the ability to restrict the accessibility of one language in some situations and the ability to keep multiple languages accessible simultaneously in other situations. • When participants are asked to switch between languages while doing a language task, activation is seen bilaterally (Hernandez, Martinez, & Kohnert, 2000; Price, Green, and von Studnitz 1999). • Bilingualism might impact non-linguistic aspects of cognition, including task switching. • Bilingual adults show an enhanced ability to attend to task-relevant dimensions of stimuli • Bilingual adults are less impacted by stimulus-response incompatibility than monolinguals (Bialystok, Craik, Klein, & Viswanathan, 2004). • Older adults with approximately equal proficiency in two languages were faster to respond in a Stroop task than participants with unbalanced proficiency in two languages (Zied et al, 2004). • Bilingual children show an advantage over monolingual children on card sort tasks which involve switching from one set of rules to another (Bialystok, 1999; Bialystok & Martin, 2004). • Participants • 60 right-handed undergraduates • 20 monolingual speakers of English who were not exposed to a second language before age 10 • 40 fluent bilinguals who currently use English and another language and were exposed to both languages before age 5 • 20 “Low Switchers”: Predominantly one language used with each individual, but that language varies across individuals • 20 “High Switchers”: Relatively even use of more than one language with each individual • Stimuli • Written language history questionnaire • ??? Trials • Half match, half no match • Of match trials, • Within VF – matching items on same side of fixation point • Across VF – matching items on opposite sides of fixation point • Two Tasks • Same – Is the bottom number the same as either of the top two numbers? • Add – Do the bottom number and either of the top two numbers add up to ten? • Two Switch conditions • No switch – Same task as previous trial • Switch – Opposite task from previous trial • Equally often switch after 1, 2, and 3 repetitions of previous task Presentation • Fixation flash (300 msec) • Colored letter to signal task (150 msec) • Simultaneous presentation of target and probes (140 msec) Monolinguals p = .73 Low Switchers p = .04 High Switchers p = .01 AHA difference between tasks greatest for high switchers and smallest for monolinguals Conclusions • The magnitude of the switch cost does not differ between monolinguals and fluent early bilinguals. Task switching difference between monolingual and bilingual children may be the result of a developmental difference rather than a performance difference. • Even when the task is switched between trials, there is an overall across hemisphere advantage for the more complex add task and not for the less complex same task. The benefits of interhemispheric interaction outweigh the costs only when the task is sufficiently attentionally demanding. • Bilinguals’ experience with the recruitment of bilateral resources enhances both the costs and benefits of interhemispheric interaction, making the difference in AHA across tasks more dramatic for bilinguals than monolinguals. Those bilinguals most likely to frequently switch between languages show the greatest task difference in AHA. Switch Cost Does Not Differ Between Language Groups Predictions • As the result of a lifetime of language switching, bilinguals will show less of a switch cost than monolinguals. • If bilinguals are able to alter processing in response to changes in task dimension, there should be a greater difference in the AHA between less and more computationally complex tasks for bilinguals than monolinguals. • These effects would be more pronounced in bilinguals who have greater experience in switching between languages. References Banich, M. (1998). The missing link: the role of interhemispheric interaction in attentional processing. Brain and Cognition, 36, 128-157. Bialystok, E. (1999) Cognitive complexity and attentional control in the bilingual mind. Child Development, 70(3), 636-644. Bialystok, E., Craik, F. I. M., Klein, R., & Viswanathan, M. (2004) Bilingualism, aging, and cognitive control: evidence from the Simon task. Psychology and Aging, 19(2), 290-303. Bialystok, E, & Martin, M. M. 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