A Bilingual Advantage in Task Switching
Bilingualism: Language and Cognition, 2010AnatPrior & BrianMacwhinney
A theoretical cognitive system that controls and manages other cognitive processes such as planning, rule acquisition, initiation and inhibition of actions or sensory information.The executive functions are often invoked when it is necessary to override responses that are automatically elicited.Miyake et al. (2000) identify three separate, but correlated, executive functions: updating of working memory, inhibition ofdistractorsor responses, and shifting between mental sets.Ex: Being presented with a piece of chocolate cake may automatically elicit a response to take a bite, yet in some cases such an action would be inappropriateEx: Ignoring surrounding sounds in order to focus solely on one.
The acquisition and dynamic interaction of multiple languages are being intensely studied within the domain of psycholinguistics.Alongside this work, there is growing interest in the possibility that bilingualism might exert its influence beyond the language system, and have implications for cognition more generally.The theory is thatextralinguisticdifferences in the cognitive function of monolinguals and bilinguals can illuminate the degree to which language production and comprehension rely on domain-general cognitive skills (O’Grady, 2005).
Recent studies of young children have providedevidence for robust bilingual advantages in thedevelopment of executive control.The bilingual advantage in executive control isassumed to stem from bilinguals’ constant need to manageand monitor their two languages. There is abundantevidence that, perhaps counter-intuitively, both languagesof bilingual speakers are constantly active, thus it seemsthat the intention to speak in one language is not sufficientto suppress all activation of the other language
The tasks used to date to explore the impact of bilingualism on executive functions –including the Simon, anti-saccade, stop-signal and flanker tasks – fall mostly into the category of inhibition rather than controlled shifting of mental sets. However, during language production, bilingualism places particularly high demands on shifting abilities, as speakers have to decide, at least in certain circumstances, when and how to switch back and forth between their two languages.Thus, it is legitimate to measure the possible effects of bilingualism on experimental paradigms that require executive shifting and not solely inhibition.
support for bilingual advantages in the ability to shift mental sets
Bialystok & Martin (2004): bilingual preschoolers successfully performed the dimensional change card sort task at an earlier age than their monolingual peers.Bialystok &Shapero(2005): Bilingual advantage in the ability to identify alternative images in reversible figures when compared with monolinguals.Bialystok,CraikandRuocco(2006): Dual task paradigm shows a bilingual advantage in performing the classification of visual images during concurrent classification of auditory information (advantage only in the visual classification). However, it was concluded that the advantage was due to enhanced bilingual inhibitory control and not the ability to switch between tasks.
Parallels between language and task switching
Similar to general task switching, a switch between languages necessitates establishing the new language set and overcoming the language set inertia of the previous trial language.Another similarity is that much like switching from an easier task to a more difficult one, switching from a dominant language to a less prevailing language results in smaller switching costs than vise versa.Finally, there is evidence that language switching and task switching may be supported by similar brain regions.In light of these parallels, higher efficiencyof bilingualsintask switching, when comparedwith monolinguals, would lend support to the ideathat bilingualadvantages in executive controlextend beyondinhibitorycontrol.
Task Switching Paradigms
include twotypes ofexperimental blocks – single-task blocks, andmixed task blocks. From this basic setup, two measuresof executivecontrol can becomputed:Switching costs- thedifference in response time between switch andnonswitchtrialsin the mixed-task blocks, and arethought toreflect the difficulty in switching from onetask setto another.Mixing costs - thedifferencein performancebetween single-task blocks andnon-switch trialsin the mixed-task blocks. Mixing costs mayreflect theactivation of global sustained controlmechanisms necessaryfor maintaining two competingtask/response sets, for monitoring the task cued or for a process oftask decisionon eachtrial.
Predictions for the Current Study
The following study made use of a dual task paradigm in which conditions would allow for both mixing costs and switching costs to emerge.The two tasks usedwere shape decisionand color decision. To maximize mixingcost bivalentstimuli (red and green circlesand triangles) were used.Significant mixingcosts and switching costswere expected for both participant groups (bilingual & monolingual),and no difference was expected inthe basicreaction times of the two groups in thesingle-task blocks.
Participants47 bilingual and 45 monolingual psychology students from Carnegie Mellon University.Bilingual participants had learned English andanother languagebefore the age of six, and usedboth languages continuouslyever since.Monolingual participants were nativeEnglish speakers, and had not studied or been exposed toany otherlanguage before the age of twelve, though somehad limitedproficiency in a second language at the timeof testing.Self reported SAT scores were used as a measure of general cognitive ability and a working memory task was conducted to ensure there were no differences in capacity.
Design and Procedure
A non linguistic task switching paradigm(graphic task cue)using shape and color. (Red\Green, Circles\Triangles). The cue was displayed on screen and remained there while the target appeared in the center.Participants were instructed toperform onetask (either shapeor color, counterbalancedacross participants)using theright hand, and the other task using the left hand.Participants completed three parts of theexperiment, comprisinga sandwich design. In the first part,they performedtwo single-task blocks (color and shape,order counterbalancedacross participants), each including8 practicetrials followed by 36 experimental trials.In thesecond part, participants performed 16mixed-task practicetrials, followed by 3 mixed-task blocks.Each mixed-taskblock included 48 trials, half of whichwere switchtrials and half of which were non-switch trials,of boththe color and shape tasks, randomly orderedwith amaximum of 4 consecutive trials of the same type.Finally, in the third part of the experiment,participants againperformed two single-task blocks, presentedin theopposite order from that used in the first part. The sandwichdesign enables a comparison of 72 switchtrials, 72non-switch trials, and 144 single-task trials (72color and72 shape).
Switching costs- While both language groups performed identically on non switch trials, bilinguals were much faster than monolinguals on the switch trials. Thus bilinguals incurred a much lower switching cost than monolinguals.Mixing costs-trials in the single-taskblocks wereperformed more quickly and accuratelythannonswitchtrialsin the mixed-task blocks. However,there wasno significant difference betweenthe groups. Therefore, both groups exhibited significant mixing costs but there was no difference in the mixing costs between the groupsTable 2.Mean reaction time in milliseconds (SEM) and% correct for singletask, non-switchand switch trials, by language group.Mixed-task blocksSingle-taskblocksNon-switchSwitchBilingualRT 437.97(11.2)670.16(28.7)814.16(33.2)%correct95.9 94.2 91.8Monolingual RT448.8(11.8) 669.05(26.7)875.54(39.2)%correct97.8 96.1 92.2
As predicted, the bilingual group displayed an advantage in the executive function of mental task switching. However, the bilingualadvantage was limited to reducedswitching costs, which arise from transient control processesfor selectingbetween competing tasks, such asactivating currenttask goals and reconfiguringstimulus–response mappings. Conversely, no group difference was foundin mixingcosts that have been related to moresustained controlmechanisms, and the ability to resolveconcurrentdistractorinterference.Switching costs have also been described asreflecting proactiveinterference (Philipp et al., 2008), andthus thepresent results support enhanced bilingualefficiency inresistance to proactive interference, a subtypeof inhibitory function.Finally, Bialystok and colleagueshave describedaspects of cognitive executive functionthat deterioratewith aging, but are enhanced bybilingualism. Thus, it is interesting to compare the current studywith theimpact of aging on task-switching performance
In conclusion, the present study demonstrated arobust bilingual advantage in performance,suggesting thatlifelong bilingualism may lead to enhancedefficiency inthe executive function of shifting betweenmental sets. Specifically, the reduced switching costs foundfor bilingualscan be linked to the process oflanguage switchingthat calls on general mechanisms ofshifting, andutilizes overlapping neural resources. Further,it is suggestthat the increased bilingual efficiency inshifting mighthave contributed to some extent to previousfindings ofbilingual advantages linked to inhibitoryfunction, especiallyin light of the correlation between thesetwo executivefunctions. Future work on this importanttopic shouldinvestigate how the cognitive consequencesof lifelongbilingualism are expressed through variationsin executive function.