Practice(orreview)tendstobuildandmaintainmemoryforataskorforanylearnedmaterial.Overaperiodofnopracticewhathasbeenlearnedtendstobeforgotten;andtheadaptiveconsequencesmaynotseemobvious.Yet,dramaticinstancesofsuddenforgettingcanbeseentobeadaptive.Inthissense,theabilitytoforgetcanbeinterpretedtohavesurvivedthroughaprocessofnaturalselectioninanimals.Indeed,whenone’smemoryofanemotionallypainfulexperienceleadstoseriousanxiety,forgettingmayproducerelief.Nevertheless,anevolutionaryinterpretationmightmakeitdifficulttounderstandhowthecommonlygradualprocessofforgettingsurvivednaturalselection.
Inthinkingabouttheevolutionofmemorytogetherwithallitspossibleaspects,itishelpfultoconsiderwhatwouldhappenifmemoriesfailedtofade.Forgettingclearlyaidsorientationintime,sinceoldmemoriesweakenandthenewtendtostandout,providingcluesforinferringduration.Withoutforgetting,adaptiveabilitywouldsuffer;forexample,learnedbehaviourthatmighthavebeencorrectadecadeagomaynolongerbe.Casesarerecordedofpeoplewho(byordinarystandards)forgotsolittlethattheireverydayactivitieswerefullofconfusion.Thusforgettingseemstoservethesurvivaloftheindividualandthespecies.
Anotherlineofthoughtassumesamemorystoragesystemoflimitedcapacitythatprovidesadaptiveflexibilityspecificallythroughforgetting.Inthisview,continualadjustmentsaremadebetweenlearningormemorystorage(imput)andforgetting(output).Indeed,thereisevidencethattherateatwhichindividualsforgetisdirectlyrelatedtohowmuchtheyhavelearned.Suchdataoffergrosssupportofcontemporarymodelsofmemorythatassumeaninputouputbalance.Questions:
1.AccordingtoPara.1,memoryplaysanimportantrolein____.
2.Wecanobviouslynoticethatoveraperiodofnopracticewhathasbee