C.
Theterm“multitasking”originallyreferredtoacomputer’sabilitytocarryoutseveraltasksatonetime.Formanypeople,multitaskinghasbecomeawayoflifeandevenakeytosuccess.Infact,someexcellentmentalaerobicexercises(人脑训练)involveengagingthebrainintwoormorechallengingactivitiesatatime.Althoughcheckinge-mailwhiletalkingonaphoneandreadingthenewspapermaybesecondnatureforsomepeople,manytimesmultitaskingcanmakeuslessproductive,ratherthanmore.Andstudiesshowthattoomuchmultitaskingcanleadtoincreasedstr ess,anxietyandmemoryloss.
Inordertomultitask,thebrainusesanareaknownastheprefrontalcortex(前额叶脑皮层).Brianscansofvolunteersperformingmultipletaskstogethershowthatastheyshiftfromtasktotask,thisfrontpartofthebrainactuallytakesamomentofrestbetweentasks.Youmayhaveexperiencedaprefrontalcortex“momentofrest”yourselfifyou’veeverdialed(拨电话)andtheanswering,yourmindshiftedtoantherthoughtortask,andthenlookthat“moment”tocomeback.Researchhasalsoshownthatformanyvolunteers.Jobefficiency(效率)declineswhilemultitaskingascomparedtowhentheyperform.onlyonetaskatatime.
Multitaskingiseasiestwhenatleastoneofthetasksinhabitual,orrequireslittlethought.Mostpeopledon’tfinditd ifficulttoeatandreadthenewspaperatthesametime.However,whentwoormoreattention–requiringtasksareattemptedatonetime,peoplesometimesmakemistakes.
Weoftendon’tr ememberthingsaswellwhenwe’retr yingtomanageseveraldetailsatthesametime.Withoutmentalfocus,wemaynotpayenoughattentiontonewinformationcomingin,soitnevermakesitintoourmemorystores.Thatisoneofthemainreasonsweforgetpeople’snames---evensometimesrightaftertheyhaveintr oducedthemselves.Multitaskingcanalsoaffectourrelationships.Ifsomeonecheckstheire-mailwhileonthephonewithafriend,theymay**offasabsent-mindedordisinterested.Itcanalsocausethatpersontomiss*overlookkeyinformationbeingpassedontothem.
49.Whyaresomementalaerobicexercisesdesignedtoengagepeopleinmultitasking?
A.Tomakethemmoreproductive.
B.Toreducetheirstr essandanxiety.
C.Todeveloptheircommunicationskills.
D.Tohelpthemperform.dailytasksmoreeasily.
正确答案：D
