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　　标题：HowaHumanScreamUniquelyActivatestheFearResponseinYourBrain
　　source：io9丨byGeorgeDvorsky
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　　Weknowhumanscreamsarejarring。They’reloud，occasionallyshrill，andtendtomakeusfeelstressed，orevenfearful。What’suncleariswhytheyelicitanxiety。Butanewstudysuggeststhisresponsemayhavesomethingtodowiththeacousticqualityofhumanscreams，andhowtheytriggerthebrain’sfearresponse。
　　AccordingtoanewstudyheadedbyDavidPoeppelfromNewYorkUniversity，andhispostdocLucArnal，nowattheUniversityofGeneva，thishassomethingtodowithauniquepropertyofsound，calledroughness，thatactivatesthebrain’sfearcircuitrywithintheamygdala。ThedetailsoftheirworknowappearatCurrentBiology。
　　RoughSounds
　　Roughnessreferstofastsoundchangesinloudness，Arnaltoldio9。Normalspeechforinstanceonlyhasslowdifferencesinloudnessbetween4and5Hzwhichisnotroughandbasicallycorrespondstothesyllabicrate。Screams，ontheotherhand，modulateveryfastbetween30and150Hzwhichisrough。
　　Arnaladdsthatthestrength（lowvshigh）ofroughnesscorrespondstotheamplitude，orvolume，ofthesefastchanges。Lowroughnesscorrespondstoweakloudnesschangeswhereashighroughnesscorrespondstohighloudnesschanges。
　　Thiskindofsoundcouldbecomparedtoastrobelightintheauditorydomain，saysArnal。Everyoneisfamiliarwiththoselightsthatflashsuperfastinclubsforinstance。Screamscouldbedefinedasstrobophones，sincetheyaremodulatingsuperfastinananalogouswayintheauditorydomain。
　　Astheirfascinatingexperimentshows，theserough，strobelikesoundsappeartohaveacurious，andpossiblyadaptive，effectonthehumanpsyche。
　　AnEvolvedResponse
　　PoeppelandArnalusedrecordingstakenfromYouTubevideos，popularfilms，andvolunteerscreamerswhowererecordedinthelab’ssoundbooth。Then，inaseriesofexperimentsinvolvingfMRIscanners，16participantslistenedtosoundsofvariousdegreesofroughness。Theresearchersusedthreedifferentcategoriesofsoundsthatwereeitherneutralorunpleasant，namely：humanvocalizations（normalvoicesandscreams）；artificialsounds（likeinstrumentsandalarms）；andmusicalintervals（bothconsonantanddissonantsounds）。Theresearchersthenidentifiedbrainregionsinvolvedinprocessingunpleasantnessbycomparingresponsestounpleasantsoundsagainstresponsestoneutralsounds。
　　Resultsshowedthatunpleasantsoundsinducedlargerhemodynamicresponses，i。e。therateofbloodflow，inthebilateralanterioramygdalaandprimaryauditorycortices。Theamygdalaisabrainstructurecrucialforregulatingemotions。
　　HowaHumanScreamUniquelyActivatestheFearResponseinYourBrain
　　Therougherthesoundwas，andthemorescaryitwasrated，themoreeffectivelyitactivatedtheamygdala，Poeppelexplainedtoio9。
　　Fascinatingly，theresearchersfoundthattheamygdala，andnottheauditorycortex，issensitivetotemporalmodulationsintheroughnessrange。
　　Theirresultssuggestthatroughsoundsspecificallytargetneuralcircuitsinvolvedinfeardangerprocessing。Thisisthefirstdirectevidenceinsupportoftheideathatroughnessisanacousticattributethattriggersadaptedreactionstodanger。Theresearchersspeculatethatthisbehavioralfeatureconfersanevolutionaryadvantage，andthatroughvocalization，whichrecruitdedicatedneuralprocessesthatprioritizefastreactiontodangeroverdetailedcontextualevaluationinotherwords，thataroughsoundcantriggeryourfearresponsemoredirectly，andthereforefaster，thansomethingyou，say，witnesswithyoureyesandprocessinyourmind。
　　Iaskedbothresearchershowtheywerecertainthatotheraspectsofthesoundsweren’ttriggeringthefearresponse，suchasspokenwords，orsomeotherfactors，likecontext。
　　Weareverypedanticresearchers，repliedPoeppel。Wematchedalltheothersounds，infactallsoundsforduration，forloudness，formanyoftheotherfeatureswecancontrol。Wetryourdamnedesttomakesurethattheoneremainingfactorisinfactroughness。
　　TowhichArnaladded：Therewasnowordspoken。Onlysyllablesandartificialsoundswereusedinthatstudy。Wealsocontrolledforotheraspects（pitchfrequency，valenceofthesound）whenanalyzingthedataandfoundthattheamygdalaspecificallyrespondedtoroughness。
　　Interestingly，theresearchersdiscoveredthatroughsoundsdon’tnecessarilyhavetobeutteredbyhumanstoelicittheresponse。Theparticipantsexhibitedsimilarresponsestoalarmsignals，suchascaralarmsandhousealarms。
　　WhenBabiesCry
　　Thoughoutsidethescopeofthisstudy，theworkofPoeppelandArnalsuggeststhatotherhumansoundsmighttriggersimilarresponses，includingthesoundsmadebycryingbabies。Andinfact，that’sexactlywhattheresearcherswouldliketofocusonnext。
　　Weareplanningtocontinueourresearchonhumanscreamsinthelab，particularlythoseofinfants，toseeiftheirscreamsareparticularlyrough，Arnaltoldio9。Thisisaparticularlyexcitingprojectbecausewearefocusingonakindofvocalizationthatseemstobeinnate。Itisoneoftheearliestsoundsthateveryonemakesit’sfoundacrossculturesandagessowethoughtmaybethisisawaytogainsomeinterestinginsightsastowhatbrainshaveincommonwithrespecttovocalization。