TESOL – Critical Period Hypothesis

Is the research challenging the Critical Period Hypothesis (CPH) sufficient to refute it?


Over the past decades, the Critical Period Hypothesis (CPH) has enjoyed popularity. It states that individuals past the age of about thirteen are worse at learning a language than younger learners (DeKeyser, 2000).

More recently, research has refined and even refuted the CPH. many researchers believe now that children have an advantage in ultimate attainment, but adults have the initial advantage in rate of learning (DeKeyser, 2000). It is also stated that there is CPH is unimportant when it comes to ultimate attainment.

However, there are questions as to whether this research is sufficient to challenge the CPH. This essay will examine the research refuting the CPH, and consider points that support or dispute that research.

Literature Review

A study by Ioup et al (2004) led the researchers to reexamine the CPH while addressing the role of talent in adult language learning. Instead, a maturational state hypothesis was proposed (Long, 1990 in Ioup et al, 2004). The term “sensitive period” is used to show that the “critical period” is not, in fact, an abrupt point at which language acquisition is suddenly more difficult. Ioup et al (2004) put forward the philosophy that different “critical periods” exist for different aspects of SLA, such as phonology, morphology, syntax, lexis and pragmatic features.

Munoz (2011) proposes that time spent learning a language is equally as important as starting age. Munoz (2011) puts forward that, in the long term, someone starting to learn at an early age, and someone starting to learn at a later age will learn equally, given the same length of time and the same input of the L2. This research came to mixed conclusions as to the effects of starting age on second language acquisition. Munoz (2011) claimed that starting age has an impact in naturalistic settings, but in a foreign language setting where there is limited input, age does not have the same advantage.

Abello-Contesse (2008) also questioned CPH, and the existence of an optimal age for learning a second language, which ceases at puberty. Abello-Contesse (2008) put forward several alternatives, including: that there exists multiple critical periods; that there are no critical periods; that there is a sensitive period rather than a critical period; and that there is a gradual decline that continues from childhood to adulthood. Abello-Contesse (2008) also suggested that all different kinds of age effects depended in large on the real opportunities for learning, particularly whether exposure to the second language begins at an early age, and is significant and sustained.

Moyer (2004) states that although biological factors such as age have an effect on ultimate attainment (UA), other factors including psychological, social and cognitive also have an effect. Moyer (2004) also stated that the age of onset (AO) should not be given a dominant role with regards to UA.

Munoz (2006) went further than this, and stated that UA is the optimal language level that a learner will realistically attain. However, he stated that the optimal level couldn’t be attained in an instructional environment, as it is not the optimal setting. This is regardless of the AO, so therefore the CPH oes not apply at least for classroom settings.

The cases for and against CPH are put forward by Birdsong (1999), who presents case studies which supporting and rejecting the existence of a critical period (CP). However, the stronger case in the book is in support of CPH. Birdsong (

Singleton & Ryan (2004) also present case studies to cover a number of positions in relation to CPH, and seem to come to the conclusion that a CP does exist. However, they also state that length of exposure is an important factor in UA.

DeKeyser (2013) was very clear in stating that early starters are better at learning language than late starters, thus supporting the relevance of CPH. It is put forward that the contention about CPH arises from methodological difficulties and conceptual misunderstandings. DeKeyser (2013) also states that there is no evidence for the misconception that children learn languages faster than adults. However, children will keep going until their UA is close to, or equal to, that of a native speaker, whereas adults rarely achieve this.

Birdsong (2009) again says that some late starting learners achieve near native language learners, but that the typical late starter is non-native like attainment. Again, Birdsong (2009) is supporting CPH. Birdsong (2009) also refers to the “end state” as being the product of language acquisition. He says there is no end state to native language learning, but for adult learners, the native language (L1) affects the acquisition of the second language (L2), and there is an end state.

Jia & Fuse (2007) looked at the rate of acquisition of different English morphemes by native speaking Chinese children and adolescents, and found that age of arrival (AoA) in America had an effect on the mastery of the morphemes. It was found that those that arrived at a younger age mastered more morphemes than those that arrived at a later age, thus supporting CPH. Those that had a later AoA tended to master less morphemes, and had a higher error rate.

Tragant & Victori (2012) looked at learning strategies of Spanish adolescents learning English in a classroom environment in Spain. The study found that younger students, close to the CP, preferred different strategies to students just a few years older. This study also found that there is a correlation between the learning strategies of the older and younger learners, and their performance in English as a foreign language (EFL). The strategies utilised by the younger learners usually led to higher grades by the younger learners. As older learners achieve lower grades, this would also support CPH in as far as younger learners have more potential for language learning.

Izura et al (2011) looked not only at AoA of foreign words, but also order of acquisition (OoA) and cumulative learning. The results of the three experiments they conducted indicated that adults are faster, and make less errors, when identifying, producing and reading aloud words they learnt early in life than words they learnt later in life. They also found that words used more often by parents were learnt quicker by children, and that frequency of these words was higher in children than in adults.

From this, they proposed that an OoA can also be implemented when teaching second language learners. It was also found that adult learners tended to learn the early acquisition words faster than younger learners, but were slower in learning later acquisition words than learners who started learning at an early age. This tends to support CPH.

As an extension of this, Gauthier & Genesee (2011) studied young children adopted from China and required to learn a second language. It was found that the older children initially learnt faster, but that he younger children had more success over equal periods of time. UA for the younger AoA children was higher than for the older AoA children.

DeKeyser (2013) sums up the research against support for CPH, by stating that there is not much research on age effects that achieves high standards of methodology, that here is no research at all that meets all the standards he thought were necessary, and that there is virtually no evidence that is clearly relevant in an educational sense.

Literature in Practice

To argue against the CPH, Ioup et al (2004) used the study of Julie, a British adult transposed to Egypt, who was forced out of necessity to learn Arabic. While Julie achieved native-like ability in Arabic, the study does not state how many other adults in similar situations around the world failed to achieve native-like ability. The case study involves two isolated individuals, so I would not accept it as evidence against the CPH. It was my own experience in China that out of the hundreds of expats I met learning Chinese as adults, very few had achived even near-native levels of the language.

Munoz (2011) is a more convincing study, as it involves a larger sample of subjects. However, I believe that it, too falls short in the respect that the sample of late starters of English learning is much smaller than the sample of early starters of English learning. Additionally, all the subjects are English language “experts” and all the subjects learnt English in a formal setting. Munoz (2011) also states in the conclusion that a large number of studies show that early starters surpass late-starters in naturalistic settings.

From my own teaching experiences, I have found Munoz’s (2011) findings about age not being an advantage in foreign language setting to have at least some credibility. I taught students in China that had started learning English as a second language, some early and some late in life. I found that some that started in their adult years had a better command of English than many that started in primary or high school. However, there were other factors as well.

Abello-Contesse’s (2008) criticism of CPH initially rests on the fact that CPH was originally formulated to explain the inability of adults to relearn impaired L1 skills, not L2 skills. Then Abello-Contesse (2008) goes on to propose not one, but four reasons why CPH is not relevant.

One aspect of Abello-Contesse’s (2008) writing is that opportunities for learning have a great effect on ability to learn a second language. I found this to be true for  a group of fifty junior high school students in Hangzhou, China. Many had lived in English speaking countries for several years, and these students had a far better command of English language than the students who had only learnt English in Chinese schools.

Because the students spent several hours a day, six days a week, learning IELTS Preparation, Maths and Science in English, there was a residual effect. All students conversed in English outside the classroom, so this gave the students who had not lived in an English speaking country the opportunity for prolonged exposure to near-native level English. As a result, many showed marked improvement.

Moyer (2004) says that factors other than age affect ultimate language acquisition, and to this extent, I feel that my observations of the Hangzhou students support those statements. Most of the students came from privileged backgrounds, not typical of the substandard conditions most Chinese live in.

Many had also largely avoided the nationalistic conditioning of the Chinese education system for at least a few years, during their formative years. Additionally, in accordance with Munoz (2006), many had learnt outside the classroom, in a naturalistic setting. However, Moyer’s (2004) work concentrates on only one aspect of post- critical period learners, that being accent. Therefore, it is not strong evidence to refute CPH.

Birdsong (1999) and Singleton & Ryan (2004) both favoured the existence of a CP, thus supporting a CPH. In my own experience in China, I have found that some learners who commenced learning in adulthood achieved a high level of language skills. However, my best group were the Hangzhou learners, who all started in early childhood, and achieved levels higher than most of the adult starters, even at the age of thirteen.

Two of these students had grown up in America from early ages – one arriving in America at two years of age, and the other at four. Both left America at about eight years of age, and continued studying at an international school in China. The one that had arrived at two years of age had a better mastery of morphemes than the other, which equates with the findings of Jia & Fuse (2007). Additionally, the student who started at an earlier age spoke better English overall, which equates to the findings of Gauthier & Genesee (2011).

From talking to the families of these two students, it appeared that the one who had started younger had both parents speaking English and Chinese at home during their stay in America, while the other student only had one parent talking English to her at home, and the main language was Chinese. Both were exposed to English at school in America. I strongly suspect that Izura et al’s (2011) findings in regard to AoA affected the students respective acquisition orders.

DeKeyser (2013) maintained that early starters will continue to learn until their UA is native or near-native level, whereas adults usually cannot do so. I had a pair of students who would seem to prove this to be true. They were government translators, and both had begun learning English at about four years of age, and one other language in high school, about fourteen years of age. Both spoke one language other than English, one speaking German and then other Japanese. It is a requirement for government translators that they speak two foreign languages.

My colleagues, one of whom was a native Japanese speaker, and the other a native German speaker, reported that the students’ third languages, commenced later in life, were of a high standard, but not near-native level. However, both had near-native level English. This would seem to support DeKeyser’s findings. They had not progressed as far in the languages they began learning later in life as they did with English, which they began early in life.

Both had been learning English for more than twenty years, and their third languages for more than ten years. They also reported that they had found different learning strategies more useful for their third languages than for English. This is in keeping with the results of Tragant & Victori (2012).

Another group of students, pilot’s at China’s Pilot Training School in Guanghan, Sichuan, had mostly started learning English later in life, either in high school or university, because they had decided then to become international pilots. However, all had near-native level English. It transpired that these pilots were training to be international pilots, where English is the international language of aviation. The large majority of pilots never achieved such high levels, so weren’t included in the international program. This is in accordance with the findings of Birdsong (2009), who said that some late starters achieve near native levels, but the typical late starter doesn’t.


From the literature, and my own teaching experiences, it would appear that there is a critical period, after which further language acquisition becomes much more challenging and a greater effort. Students who had started learning a second language before puberty, or around 13 years of age, generally learnt better than students who started after that age.

While there were some students who started learning after the CP that achieved near-native levels, they were the minority, and not the general rule. Additionally, little of the research refuting CPH met high standards of methodology, and there is virtually no evidence that would reach academic standards.

Therefore, my answer to the research question is that preliminary investigations would suggest that the evidence refuting CPH is not sufficient.

Reference List

Abello-Contesse, C. (2008). Age and the critical period hypothesis. ELT Journal, 63(2), 170-172.

Birdsong, D. (1999). Second language acquisition and the Critical Period Hypothesis. Mahwah,NJ: Erlbaum

Birdsong, D. (2009). Age and the end state of second language acquisition. In W. Ritchie & T. Bhatia (Eds.), The new handbook of Second Language Acquisition. Amsterdam: Elsevier.

DeKeyser, R. M. (2000). The robustness of critical period effects in second language acquisition. Studies in Second Language Acquisition 22: 499-533.

DeKeyser, R. M. (2013). Age effects in second language learning: Stepping stones toward better understanding. Language Learning, 63, 52-67.

Gauthier, K., & Genesee, F. (2011). Language development in internationally adopted children: A special case of early second language learning. Child Development, 82(3), 887-901.

Ioup, G., Boustagui, E., El Tigi, M. and Moselle, M. (1994). Reexamining the critical period hypothesis. Studies in Second Language Acquisition 16: 73-98.

Izura, C., Pérez, M. A., Agallou, E., Wright, V. C., Marín, J., Stadthagen-González, H., & Ellis, A. W. (2011). Age/order of acquisition effects and the cumulative learning of foreign words: A word training study. Journal of Memory and Language, 64(1), 32-58.

Jia, G., & Fuse, A. (2007). Acquisition of english grammatical morphology by native mandarin-speaking children and adolescents: Age-related differences. Journal of Speech, Language, and Hearing Research, 50(5), 1280-99.

Moyer, A. (2004), Age, accent and experience in second language acquisition: An integrated approach to Critical Period inquiry. Clevedon: Multilingual Matters.

Munoz, C. (2006). Age and the rate of foreign language learning. Clevedon: Multilingual Matters

Munoz, C. (2011). Input and long-term effects of starting age in foreign language learning. International Review of Applied Linguistics in Language Teaching, 49 (2), 113-133.

Singleton, D. & Ryan, L. (2004). Language acquisition: The age factor. Clevedon: Multilingual Matters 2nd edition.

Tragant, E. & Victori, M. (2012). “Language Learning Strategies, Course Grades, and Age in EFL Secondary School Learners”. Language awareness , 21 (3), p. 293.


One thought on “TESOL – Critical Period Hypothesis

  1. Wonderful text, Craig. Exactly what I needed in order to present next week. However, I must say that (also from studying and from experience) CPH places a lot of emphasis on age when it is clear to me that what really plays a vital role is the environment. Suppose we could recreate the exact same conditions of an infant acquiring language to an adult learner: Need to communicate with the world; lots of exposure (also long-term); regulated sleep (which contributes to memory consolidation; reduced levels of negative stress; less judging, etc. Don’t you think the adult would display a certain advantage in language acquisition? Considering that an adult learner has a lot more previous knowledge than an infant. Another point to be made is that children will reach a more limited proficiency, if we choose to regard age as the central variable, from studying let’s say 8 years (from 5 to 13 for instance) when compared to adults who study the same amount of time. An adult learner would be capable of reaching a CEFR C2 level when a kid would most likely be able to pass the FCE or CAE exams (CEFR B2 and C1 respectively). Are you familiar with Dr. Avi Karni’s paper on second language acquisition? He concludes that older students, after CP (depending on the author you choose), perform better than younger children. Dr. Tracey Tokuhama-Espinosa discusses in one of her lectures some facts and myths of bilingualism (you can watch it here: https://www.youtube.com/watch?v=420EHD4TfOU&t=3575s&list=PLuejVFj3iC4fuE_v6Nb25miJbDNfalPrE&index=1). She discusses the works of several authors who claim that adults are actually better learner than kids.

    In the end, you’re probably right when you say that your conclusion is that there’s a period in which language learning is potentiated, however, to me it’s more about other factors rather than age.

    Posted by André Hedlund | August 28, 2017, 01:22

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