1Weeks 2-3.The Critical Period HypothesisCAS LX 400Second Language AcquisitionL1A vs L2A• Some properties of L1A:– Fast– Seemingly effortless– Uniformly successful in reaching target.• Some properties of L2A:– Slow– Hard– Typically does not end in native-like ability.Child L1A: fast, easy, successful.Adult L2A: slow, hard, failure-prone.• Suggests that kids are “built to learnlanguage” in a way that adults are not.• Perhaps there is a “sensitive period” early inlife where one absorbs languages? Asensitive period which ends at some point…Lenneberg 1967• Lenneberg 1967 is usually considered to bethe written origin of this idea that there is a“critical period” or “sensitive period” forlanguage acquisition.• He based this on several observations,including the observation that criticalperiods are biologically common.What makes us think there mightbe a critical period?• Concerning L1A, there are (traumatic) casesof delayed language exposure whichtogether seem to show that only if recoveredbefore age 10 would normal L1 languagedevelopment occur. This includes Genie(started at 13;7, learned some but stoppedshort of native-like attainment inmorphology and syntax)What makes us think there mightbe a critical period?• Another case of severely delayed language access(but without abuse) is Chelsea, misdiagnosed asretarded in early childhood, when in fact she wascongenitally deaf—only discovered when Chelseawas 31.• Chelsea’s utterances have almost no discernablestructure at all; her speech was less language-likethan Genie’s.2How early is early enough?• Isabelle (imprisoned with her mute, uneducatedmother), starting at 6, rapidly caught up to normalage-levels.• Jim, hearing child of deaf parents, brought intospeech contact around 3;6, rapidly caught up inspoken language, reaching age-norms by 6.How early is early enough?• Newport & Supalla’s study of ASL as L1 amongcongenitally deaf individuals, who started learningASL at different ages.– Exposure before 6 yields native competence, uniformerror types (4-6 did slightly less well).– Exposure after 7 yielded more errors in closed-classitems, later correlated with evidence of more“holistically” (rote?) learned elements.– Exposure after 12 much higher error rate and variableerror types, more frozen forms.Seems clear enough• There is some kind of advantage to L1Awithin the “sensitive period”.• Is it language specific? Or is theresomething about overall cognitivedevelopment that can explain this?• Once you get L1 within the sensitive period,is that good enough (does that “get itstarted”) for L2A even after the sensitiveperiod?To reiterate…• Is there a critical period for L1A?– Evidence just reviewed suggests probably.• Does this critical period affect L2A?– Is it easier to learn an L2 inside the critical period?– It is possible to learn an L2 outside the criticalperiod?– Does it just depend on having learned an L1 insidethe critical period?About critical periods• Just a note: It’s pretty uncontroversial that there issome decline in the ability to learn language thathappens with age. Nobody disputes the fact thatit’s harder to learn a second language later in life.• The question is: Is this caused by an irreversibleneurological change? (A critical period) Is itimpossible to “learn an L2” after the end of thecritical period? Or does it just get harder to learnstuff as you get older? Why does it seem to beparticularly acute with language learning?About knowledge• We can borrow from Krashen a distinction betweentwo types of knowledge:– language competence (acquired competence)– learned linguistic knowledge• The first is generally unavailable to consciousreflection. The second is quite often conscious.– An L1 example of LLK is Don’t end your sentenceswith a preposition, which if followed threaten to result intravesties like: This is the sort of pedantry up withwhich I will not put!3About knowledge• The critical period hypothesis is about obtaining acquiredcompetence (not learned linguistic knowledge) and it makesa claim about whether an L2 speaker can obtain a native-like competence of an L2.• People can always gain LLK in an L2 as well, learn rules,apply them, maybe get so practiced at it that it becomessecond nature, but this still wouldn’t rise to the level ofacquired competence.L2A and age of initial exposure• Adults proceed through early stages ofmorphological and syntactic development fasterthan children (time and exposure constant).• Older children acquire faster than youngerchildren (morphology and syntax; time andexposure constant)• Child starters outperform adult starters in the end.• So, age improves rate, at least initially, butnegatively affects ultimate level of attainment.Phonology—6• Studies of phonological acquisition suggestthat 6 years old is a critical one forattainment of native-like phonology.• Generally tested by having native speakerjudges listening (to accent, presumably) andguessing which were native speakers andwhich weren’t.Morphology, syntax,semantics—15• A few studies (including Johnson &Newport 1989) show that L2 speakers withan initial exposure prior to 15 didsignificantly better than L2 speakers with aninitial exposure after 15 in the domain ofsyntax and morphology.Comprehension—10• A small set of results (Oyama 1978, Scovel1981) suggest that ability to comprehend“masked” speech and recognize foreignaccents has a discontinuity at around age10.Several “critical periods”• So it seems that there is an age-sensitivity,but it is not even language specific, it issubpart-of-language specific.– Phonology—6– Morphology, syntax, semantics—15– Comprehension—10–…?4Why isn’t it strange that thereshould be (a) critical period(s)?• There are critical periods attested all over thebiological world.• The visual system is a favorite example. Inexperiments done on macaque monkeys, it wasdetermined that there is a critical period fordevelopment of binocular vision cells in the visualcortex (tested by monocular deprivation)• Recovery after CNS damage: disappointinglylimited in the adult brain, but can be nearly 100%in the immature nervous system.Why isn’t it strange that thereshould be (a) critical period(s)?• Vision studies replicated in cats.• In fact, vision studies “replicated” in humans as well; thereseems to be a visual critical period at