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Reading PracticeColorblindnessAMyths related to thecauses andsymptoms of colorblindness”abound throughouttheworld.The termitself ismisleading,since it is extremelyrare fbranyone tohave acompletelack ofcolor perception.By lookinginto the myths related to color blindness,one canlearnmany factsabout thestructure andgenetics othe human eye.It isa myththat colorblindpeoplesee theworld asif itwere ablack and white movie.There arevery fewcases ofcompletecolorblindness.Those whohave acomplete lackofcolor perception arereferredto asmonochromatics,and usuallyhave aserious problemwith theiroverall visionas wellasan inability to see colors.The factis thatin most cases of colorblindness,there areonlycertain shades that a person cannot distinguish between.These peopleare said to bedichromatic.They maynot beable totell thedifference betweenred andgreen,or orangeandyellow.A personwith normalcolor visionhas whatis calledtrichromatic vision.Thedifferences betweenthe threelevels ofcolorperceptionhave todo withthe cones in thehumaneye.A normalhumaneyehas three cones locatedinside theretina:the redcone,thegreen cone,and theyellow cone.Each conecontains aspecific pigmentwhose functionisto absorbthe lightof thesecolors and the combinationsof them.People withtrichromaticvision have all threecones inworking order.When one of thethreeconesdoes notfunctionproperly,dichromatic visionoccurs.B Somepeople believethat onlymen canbe colorblind.This isalso amyth,though it is notcompletelyuntrue.In anaverage population,8%of malesexhibit someform ofcolorblindness,while only
0.5%of womendo.While theremay besome truthto theideathat moremen havetrouble matchingtheir clothingthan women,the reasonthat colorvision deficiency is predominant inmales hasnothing todo withfashion.The factis thatthegene fbrcolorblindness is locatedon theX chromosome,which menonly haveoneof.Females havetwo X chromosomes,and ifone carries the defective gene,the otheronenaturally compensates.Therefore,the onlyway for a femaleto inheritcolorblindness isforboth ofher X chromosomes tocarry thedefective gene.This iswhy theincidence ofcolordeficiency issometimes moreprevalent inextremely smallsocieties thathavealimitedgene pool.C It is truethat allbabies areborn colorblind.A baby!s conesdo notbegin todifferentiatebetween manydifferent colors until heis approximatelyfour months old.This iswhy manyof the modemtoys fbrvery youngbabies consistof blackandwhitepatterns orprimarycolors,rather thantraditional softpastels.However,some currentresearch pointsto theimportanceof developingan infantscolor visualsystem.In2004,Japanese researcherYoichiSugita ofthe NeuroscienceResearch Instituteperformed anexperiment thatwouldsuggest thatcolor vision deficiency isntentirely genetic.In hisexperiment,he subjectedagroup ofbaby monkeysto monochromaticlighting forone year.He latercompared theirvisionto normalmonkey whohad experiencedthe colorfulworld outdoors.It wasfoundthat thetest monkeyswere unableto performthe color-matching tasksthat thenormalmonkeys could.Nevertheless,mostcasesofcolorblindnessare attributedto geneticfactorsthat arepresent atbirth.D Partofthereason there are somany inconsistenciesrelatedtocolorblindness,or colorvision deficiency asit iscalled inthe medicalworld,is thatit isdifficult toknow exactlywhichcolors eachhuman cansee.Children aretaught froma veryyoung agethat anappleis red.Naming colorsallows childrento associatea certainshade witha certainname,regardless ofa color visiondeficiency.Someone whonever takesa colortest cangothrough lifethinking thatwhat theysee asred iscalled green.Children aregenerally testedfbrcolorblindness atabout fouryears ofage.The Ishihara Test isthe mostcommon,thoughit is highly criticized1because it requires that children have the ability to recognizenumerals.In the Ishihara Test,a numbermade upof coloreddots ishidden insidea seriesofdots ofa differentshade.Those withnormal visioncan distinguishthe numberfrom thebackground,while thosewith colorvisiondeficiencywill onlysee thedots.E Whilemany ofthemythsrelatedtocolorblindness havebeen bustedby modemscience,there arestill a few remainingbeliefs thatrequire moreresearch inorder to be labeledasfolklore.For example,there isa long-standing beliefthat colorblindnesscan aidmilitarysoldiers becauseit givesthem the abilityto see throughcamouflage.Another beliefis thateveryonebecomes colorblind in anemergency situation.The basisof thisidea is that acatastrophicevent canoverwhelm thebrain,causing itto utilizeonly thosereceptorsneeded toperform vitaltasks.In general,identifying coloris notconsidered anessentialtask ina lifeor deathsituation.Read thepassage andanswer thequestions.Use yourpredicting skills.Note thetype ofquestions.Questions1・5Choose thecorrect headingfor eachsection fromthe listof headings.There aremoreheadings thansections,so youwill notuse themall.Section A2Section B3Section C4Section D5Section EiColorblindness1in differentcountries iiDiagnosing colorblindnessiiiWhat iscolorblindness ivCuring colorblindnessvUnsolved mythsvi Animalsand colorblindnessviiDeveloping theabilitytosee colorviii Colorblindness andthesexesOuestions6-8Choose thecorrect letter,A,B,C,or D.6People whoseecolornormally arecalledA monochromatic.B dichromatic.C tichromatic.D colorblind.7Children usuallybegin tosee avariety ofcolors bythe ageofA onemonth.B four months.C oneyear.D fouryears.8Children whotake theIshihara Testmust beable toAdistinguish letters.B writetheir names.C readnumbers.D namecolors.Questions6-8Completing aSummaryThere aremore answersthan spaces,so youwill notuse themall.Itisa common9that onlymen suffer from colorblindness.On average10than tenpercent ofmen havethis problem.Women havetwo
1.iii.What isColorblindness Paragraph A discusseswhat peoplethink colorblindnessis,andwhat itreally is.In themiddle ofthe paragraphit states,The factisthatin mostcases ofcolorblindness,thereareonly certainshadesthatapersoncannotdistinguishbetween.Thesepeople aresaidto be dichromatic.
2.viii.Colorblindnessandthe Sexes.Paragraph Bdiscusses thefact thatmen aremore pronetocolorblindness thanwomen,and statesthe geneticreasons whythis isthe case.
3.vii.Developing theAbility toSee Color.Paragraph Cdiscusses thefact thatbabies arealt borncolorblindand thatthey do not developtheabilitytoseecolorsuntilthey areafewmonthsold.This paragraphalso discusses the possibilitythat infantsmay requirea colorfulenvironment inorderto developproper colorvision.
4.ii.diagnosing Colorblindness.Paragraph Rdiscusses thereasons whycolorblindness isdifficultto diagnose.It alsodiscussestheIshiharaTest,which distinguishesthose whoare colorblindfromthose whohave normalcolorvision.
5.v.Unsolved Myths.Paragraph Ementions twobeliefs aboutcolorblindness thathavent beenprovenas myths:that colorblindnesscan aidmilitary soldiersand thateveryone iscolorblindinanemergency.
6.C Thesecond tothe lastsentence ofParagraphAstates that:People withtrichromatic visionhaveall threeconesinworking order.
7.B Thesecond sentencein ParagraphC statesthat:A baby*s conesdonotbegin todifferentiatebetween manydifferent colorsuntil heis approximatelyfourmonthsold.
8.C ParagraphR statesthe maindownfall oftheIshiharaTest:The IshiharaTest isthe mostcommon,though itishighlycriticized becauseitrequiresthatchildrenhavetheability torecognizenumerals.
9.myth.Paragraph Bintroduces theidea thatalthough colorvisiondeficiencyispredominantinmales,itisstill possiblefor femalestobecolorblind.
10.alittleless.Paragraph Bstates:In anaverage population,8%of malesexhibit someform ofcolorblindness.
11.Xchromosomes.Paragraph Bstates:Females havetwo Xchromosomes.
12.less likely.Paragraph Bexplains thatitislesslikelyfor womentobecolorblind,because ifoneof theirXchromosomescarriesthedefectivegene,the otherone naturallycompensates.Compensate meansto makeup foranothers weakness.。