Lecture 11

[Music] hello and welcome to the course introduction to the psychology of bilingualism and multilingualism this is the third week of the course and I'm Dr arwma from the cognitive science department at I kpur in the last lecture we've talked a little bit about various stages of language acquisition mainly with a focus on first language acquisition but also simultaneously keep having an eye for how are individuals acquiring their two or three four languages simultaneously one of the very interesting aspects of this uh uh you know exercise of language acquisition is the chronology of how this happens and basically does this chronology have any boundary conditions for example uh are the developmental Milestones that we discussed for example in KS 2003 uh you know description of what happens at what age for these children are these Milestones really watertight or are they overlapping with each other or say for example if a child misses these Milestones what are the consequences for that all of these debates in some sense are gathered around a particular very influential hypothesis in the field of language learning which is known as the critical period hypothesis for language learning in today's lecture and the lecture after this I'm going to sort of uh take a detailed look at this critical period hypothesis uh basically with a view to understanding is there a critical period at all that limits or let's say gives a sort of a boundary condition for language learning in today's lecture I'll talk more about the critical period in terms of first language acquisition whereas in tomorrow's lecture I'm going to talk a little bit more in detail about whether there are critical where whether there can be a critical period or let's say age of acquisition kind of effect effect in second language learning let us begin now the critical period hypothesis uh you know as bird song aptly summarizes is basically uh to the tune that uh there is a limited developmental period during which it is possible for individuals to acquire a language whether it is their L1 or their L2 to normal or native like levels what is native like level I'll come to that and I'll talk about that as well but the idea is that this is a biological or intellectual sort of uh uh you know it's it's mainly housed in a biological argument which basically says that once this window of opportunity is passed the ability to learn languages steadily declines over time and in some sense a consequence of this hypothesis would be that while children will be very good children are in fact very good at picking up languages uh you know very swiftly uh the ability to pick up new languages learn new languages apparently should diminish or does diminish when when people of you know growing age say for example the older you get the harder it becomes for you to grasp another language now is this is this actually true should we sort of look around ourselves uh have a look at particular examples and do we find that this is actually the case this is something I would invite you to ponder upon uh because if that is then there must be either biological or intellectual cognitive factors that might be governing this the critical period hypothesis as I just said is more of a biological hypothesis that basically uh you know is in line with chomskian ideas of innate language specific learning capabilities uh rather than actual factors uh you know which are housed in cognitive theories or functional descriptions so the critical and also in in one of the in one sense if you look at the critical period hypothesis you might look at it as a summation of the general notion that acire acquiring new skills any skills be it language or otherwise gets progressively more difficult with age even if you were to learn driving or swimming at a later age let's say you decided to go to learn swimming at the age of 40 45 50 maybe uh it is that much harder for an individual to learn swimming at a at that age rather than if the individual were learning to swim let's say at 3 four 5 years of age more specifically uh you know if you look at this in more detail you would find that some forms of skill learning may require very specific stimulations so for example if you want to learn uh gymnastics uh you know a particular kind of training is required if you want to learn uh speaking a particular language a particular kind of training is required uh although when I'm talking about first language acquisition there's typically not really uh explicit language instruction that uh parents engage in but there is obviously that particular kind of input that is required for individuals to learn language okay uh interestingly people of uh reason that this training or this exposure to this external stimulation must happen within a particular bounded period of time within which its effects are most optimal uh and out of which the effects are slightly uh you know less effective for that matter say for example if somebody were to take uh swimming classes you know uh every day the swimming classes every day that you take at the age of three or four years might be more helpful than if you take the same kinds of sing classes every day at the age of 45 5050 55 and so on so the same kind of stimulation works better when it happens within a particular bounded period of Time Versus if it works outside that bounded period of time let's take an example the song but chinch uh must be exposed to the male song of its species within 10 to 15 days of its birth otherwise it would not be able to develop the similar singing skill similarly with ducks I'm sure you would know that ducklings need to be imprinted or say for example need to be attached to their uh mother immediately after birth otherwise what would happen is that they would attach themselves they would have this irrevocable sort of attachment with any moving object or things that they would you know come across uh you know minutes after birth it could be uh you know even a crocodile uh you know Flo swimming around in the river or let us say a twig or any other thing for that matter so there are instances in nature where uh you know there is this need for a Time bound stimulation and if this stimulation does not happen with a Time bound period it leads to semi-permanent uh changes I will not call them irreversible but semi-permanent changes that would happen with the biology uh you know of the of the individual in question so the critical period hypothesis for language learning therefore has been favored for uh by experts from linguistics psychology Neuroscience foreign language teaching and even policy makers you could see some of the policies that exist in our schools uh some of the things that we sort of talk about even in the new education policy for example there is a lot of stress on teaching a lot of skills very early in life there's a lot of stress on what kinds of skills need to be imparted at what age because in some sense the uh idea is to align the cognitive and biological capabilities of an individual uh with the kind kind of pedagogic IAL you know instructions that they are being imparted with interestingly the critical period hypothesis comes in various shapes and forms uh one of which basically is made by let's say you know Penfield who says that the superior language learning skills of young children is due to the higher plasticity of brain the higher brain plasticity that is available to younger children as opposed to older individuals and he goes on to say that this higher plasticity is because when you are grow growing uh you know at early ages uh diminishes because at later ages the myelination of the you know neurons is finally complete and no no and fewer new connections can be formed and etc etc this is one way of looking at it the other way of looking at it was put forward by lenberg in 1967 who says that you know the critical period of language learning basically has something to do with the progressive lateralization of the brain so the idea is the brain is maturing it is you know it is sort of uh uh reaching its uh eventual uh final developmental stages by the age of 8 n years and this is around the time where the brain is also getting lateralized later what does lateralization mean uh just to give you a brief recap from some of the earlier lectures that I may have taken literalization basically refers to a relative uh specialization of either of the two hemispheres for a particular skill in in our case it is very uh well linked to the left hemisphere because the left hemisphere of the brain is supposed to be specialized for language functions whereas the right hemisphere of the brain is supposed to be specialized for non-l language functions Vision emotion those kind of things now lenberg basically says that our brain starting from birth is getting progressively literalized every uh you know with every passing day because of the new information it is getting and one of the key drivers of this literalization or you know in that sense is the lateralization towards the left hemisphere for language and towards the right hemisphere for other verbal activities lenberg basically says that around birth both the hemispheres are equip potential however as a consequence of measur that that is growing with age lateralization uh you know is in some sense getting culminated gradually and during this process the left hemisphere sort of becomes more and more specialized for language now uh I mean this in in some sense you can say call this as a culmination of the maturational period as well or the culmination of the lateralization process as well the sum total of that is that by the time these two processes are complete the left hemisphere should be should have already become specialized for speech whereas right hemisphere for non-verbal functions they're linking this to the crtical critical period hypothesis in a way that once the literalization or the maturation process is complete uh newer skills especially language is harder to come by is more much more harder to learn because whatever inputs that the brain had to take during this lateralization for language was happening is already assumed complete by that time if something happens after this it will delay that entire process or it'll make it that much more harder for the brain to pick up these new skills so the progress of uh lateralization or the progress of lateralization as you know the an individual is growing up uh is also supposed to be accompanied by the decreased plasticity of the brain which in some sense basically you know According to some biological uh researchers uh culminates at around puberty so around 10 11 years which is where the critical period also ends and basically uh what we are now saying is that by the end of pu puberty by the end of the period that the brain is reached its you know penultimate or ultimate stages of maturation lateralization is complete myelination is complete plasticity is limited and these are you know a bunch of biological explanations that people have put forward in order to explain uh you know the so-called diminish ability of older people in learning new languages now is that really the case we can sort of you know uh zoom in and look more closely at the evidence that there is before we move on to individual cases another supporting idea for the notion of this critical period is the relatively better recovery of language functions in children uh in children compared to adults following brain damage due to an injury so it has also been observed a lot of neuros pychology have observed and reported this that uh when in individual suffers from brain inj brain injury supposedly to the left hemispheric areas of the brain which are supposed to be specialized for language uh the younger children actually recover from that much earlier and uh you know the recovery is more uh more is is better it's uh you know uh as compared to when older people sort of have a brain injury let's say have a stroke or something they do not seem to fully recover from the effects of that injury and this basically happen s you know owing to the higher plasticity of the brain of these younger children so for example if if a younger child suffers from accident and areas of the left hemisphere are damaged what would typically happen is that because the brain is still maturing and the activity in the brain's maturation is is still going on uh other surrounding areas of the uh brain uh surrounding the damaged areas sort of take up the language functions all right so this is again something that has to do again with this higher plasticity in younger brains as opposed to older brains and so on finally the idea of a critical period as I said earlier as well is supported by chomsky's proposal of the universal grammar or a species specific language learning device and the idea is that it species specific language learning device uh basically Works upon the input that it is receiving from the environment to allow us to learn language once the uh you know the brain is reached its maturational uh uh you know uh stage or once the progressive literalization is complete it basically happens that this language learning device if it has not received any input during these early years uh you know of an individual's life uh this language learning capability or whatever the neural basis of this language learning capability is it veers off it gets destroyed it gets diminished and its ability to allow us to learn and pick up several new languages also Fades away and goes away so the idea is it is the time it is very time specific it is very time sensitive that individuals get the proper linguistic input and the proper environment to learn a language within this specific bounded period of time because this will allow them to learn language to the best probable extent that they can as opposed to if this simulation arrives slightly later in life when all of these three processes uh you know Pro myelination Progressive uh lateralization maturation have completed so in in some sense so far we've seen that the critical period hypothesis is actually uh more of a biological hypothesis that sets aside uh conditions uh within which language learning can happen and after which language learning becomes increasingly more difficult now let us look at you know age of acquisition effects for the first language you know what really happens depending upon when the individuals pick up language typically for most of us it happens that we are acquiring uh you know in input uh related to language since birth or if you remember the previous lecture n minus 3 months after birth which is when our auditory systems have already developed now uh children uh and it happens it has been reported in some very rare cases that childrens who have not been exposed to somehow uh to reach linguistic input since birth have eventually been found to uh you know have restricted linguistic development going forward and interestingly these children offer a very interesting opportunity uh in terms of studying language acquisition and its breakdowns uh whenever you know this really uh takes place uh and there are different types of scenarios where these kind of cases have been discovered uh typically it has happened uh you know typically these people these children have been referred to as feral children uh basically children who are reared in the wild or grew up in the wild reared by wild animals and there are two or three categories of these kind of children that you know have been documented and we're going to talk about them firstly children who are deserted in the wild and have been supposedly raised by animals such as wolves or monkeys and so on and so forth an interesting case of this type was that of uh two girls uh found in midnapur in India uh back in the 1920s called kamla and amla uh kamla was around 6 to 8 years when discovered amla was around 4 to 6 years when discovered they were both discovered in a Wolf Den and were taken to an orphanage by that by a missionary named Joseph Singh Who start who immediately put them on language training and you know other kind of uh you know uh behavioral training that is expected of girls of this age now interestingly these girls were being apparently being raised by the Wolves now Kamala the older kid who's probably already pass this critical period that we are talking about after 3 years of training could Master only about 40 words you know something that a normal 2-year-old could probably mastered within a week or a fewer days all right and even though whatever words she was learning were and when she would try to speak them would be phonologically UND specified the details the phones will not be as uh you know uh presented in that much detail as opposed to uh you know even for example compared to a 2-year or a three-year-old normal developing child kamla died at the age of 16 due to typhoid infection and although the younger sister Amala who was basically you know uh making slightly better progress than kamla given that she was still in this critical period uh you know that we have talked about uh she also Fel very very quickly and died within a year of being discovered so again while there is some trend of the importance of critical period the evidence is not really conclusive so we can go to another type of feral children that have been discovered it could be something those say for example there's a case of this boy called Victor you know from avaron you know Aon Forest near the near the city of tulus in France Victor was discovered at the age of 12 years and was trained by jeam Mark itard who was a medical student at that time uh interestingly you can note that uh Victor has also been discovered post the uh you know critical period and what happens is that even after 5 years of rigorous training uh you know Victor showed almost zero progress with respect to learning language and the only couple of words that he could actually Master eventually were o de basically meaning oh God or Le which is milk so other than that the child has not been able to pick up anything uh because probably he was discovered after the critical period had already passed finally a third category of such children whose Behavior resembles that of Federal children but they have not been raised in a wild environment but let's say within the human familial environment but have been kept devoid of any kind of linguistic input or human interaction for instance say for example some of these children that we could talk about were actually kept confined to a room a Cellar kept logged not allowed to speak not allowed to hear any kind of linguistic input and then when they were discovered and rescued uh their language abilities at that time were assessed and then it was also says that okay how did they improve with human contact with better living conditions and so on and so forth a very interesting case uh of of such a kind is that of oana Malaya who was a Ukrainian girl who spent the life who spent her life between 3 to 8 years of age in a dog kennel behind her house so she was basically somehow deserted by her parents and she spent three to the time of 3 to 8 years in her life in a dog Kel just behind her house uh when she was discovered she was found to be you know her behaviors were found to be resembling that of dogs she would walk on all four she would bark growl sniff at her food and so on and so forth interestingly if you type oan amalaya on YouTube you'll be able to find a very long sort of uh one one or two hour documentary uh that sort of describes her and you will see that it's it's very interesting that by this time you know when this documentary is made she has actually gained a bunch of language functions which probably would not there uh when these tests were being conducted so uh oana also could not learn language to the you know to any significant uh extent uh because when she was discovered she was already P what is referred to as a critical period final notable case in this uh uh you know in this category or in this variety uh could be that of the girl called Genie who was discovered in 1970 in a Los Angeles suburb now Genie was kept in a linguistically impoverished environment from the age of around 20 months to 13 years she had been kept logged up in a room tied to a potty chair uh with no uh you know permission to make any kinds of noises or even uh the input of any kind of human uh conversation was sort of very very minimal almost non-existent for her all right uh her father was obviously uh you know had some kind of mental issues and you could not tolerate any noises so Genie was not allowed to make any sounds moreover the household was also completely quiet she was rescued around the age of 12 or 13 and once rescued she was first moved to a child's hospital where the only speech uh she could produce were words like stop it no more or Sorry probably arising from you know her predicament in uh in in that particular place now uh Genie was uh in some sense or her training was undertaken by Victor frin a psycholinguistic from UCLA uh and uh her and his uh graduate student Susan Curtis uh who basically tried to rehabilitate Genie and uh you know help her grasp aspects of intelligence as well as aspects of language as well now uh according to Curtis's records uh within four years of her rescue Genie clearly attained most of the aspects of operational intelligence including uh that of uh you know a figurative thought uh moreover she could also demonstrate fully developed and Superior abilities in the domain of visual and spatial function so some of these aspects of you know children being intelligent is were very evident were pretty apparent in Genie however when you read Susan Curtis's reports it basically tells us that the linguistic repertoire of uh Genie uh was slightly atypical atypical in the sense that although within you know a few months of her Discovery she had begin to produce single words couple of months later later she had acquired a productive vocabulary about of 100 to 200 words and had also started to combine words the development of morphological and syntactic aspects of language were slightly impoverished uh according to the earlier reports Genie could not pick up comparable development of morphology and uh you know syntax uh such as tenses word order fixes you know also things like prepositions auxiliary verbs you know I will do this I will do that and so on and so forth and uh this basically led the researchers to believe that while Genie is being able to at least understand word meanings which is basically referential lexical knowledge she's typically being able to pick up what a word means say for example this is a pen this is a watch and so on she was being able to do that but she was not being able to master aspects of grammar which basically tells us maybe this critical period uh talks more about the development of syntactical capabilities rather than picking up semantic relations uh from the conceptual environment and the research actually actually published a bunch of papers documenting Genie's press in language learning and so on and so forth however uh years later probably you know a couple couple of decades later when this data was relooked at and a lot of researchers sort of went back and started uh looking at this data it was discovered that actually Genie was progressing rather well she was able to pick up a bunch of aspects of a syntax as as well as morphology and what probably was happening was that due to some kind of an experimental bias uh some of those aspects were being ignored by the experimenters or being treated as fluke or being treated as something that she's just done by chance and will not be able to replicate later so this here is a very interesting case of you know experimenters and scientists uh being in some slightly uh you know restricted in their Vision or interpretation by the idea that they already have obviously frin and Curtis probably believed more in the critical period hypothesis which may have led to you know some uh uh let's say a harsher interpretation of uh Genie linguistic skills then was basically warranted by her linguistic Behavior because a lot of later research actually talks about the fact that Genie did eventually pick up some aspects of grammar and uh you know morphology uh which were obviously overlooked by these earlier researchers so to summarize the critical period hypothesis seems to be able to predict a period of optimal learning for the first language which is let us say within this bound of critical period till puberty or up to 8 nine years and so on however the evidence uh for individuals you know whove missed this critical period is actually rather hard to take into account even if you talk about Kamala and amla or Victor or Genie or oana uh all of the these evidences are slightly underdocumented a bunch of these things uh may get confounded by experimenters bias uh bunch of these things uh basically so because we cannot really create an experiment around this we cannot actively control for all conditions and keep somebody isolated without linguistic input for any length of time uh a bunch of these things are not really testable and demonstrable in that sense so the evidence for the critical period hypothesis although it is part of folklore and common wisdom these days and has always been uh the part of the evidence for the critical period hypothesis uh especially for first language acquisition looks sketchy at best all right so in the next lecture I will talk about some of the related effects of critical period or age of acquisition for second language learning in bilinguals and multilinguals thank you so [Music] much [Music] [Music]