Many interpretations of the research findings of the critical period hypothesis (CPH) have caused controversy. This thesis seeks to clarify the controversies surrounding CPH testing and determine what data would provide evidence for the hypothesis. The approach used is to discuss some of the difficulties in interpreting important empirical studies in the light of different formulations of CPH and the way of understanding CP for language acquisition.
The main issues are: age and the acquisition of different rule types, post-maturational age effects, the influence of the L1, and native-like achievement.
Introduction
These factors contribute to the fact that there are a large number of controversial issues surrounding the interpretation of the results obtained by empirical studies testing the CPH, and that there is no general consensus on the data that could provide evidence for the hypothesis . The purpose of this article is therefore to discuss the controversial issues surrounding testing of the CPH and to clarify what types of data can be interpreted as evidence for the CPH in light of the different formulations of the hypothesis and the characteristics of the CPH . putative CP for language acquisition. The article is structured as follows: first I will provide a definition of the CP for language acquisition, followed by an overview of the various theoretical explanations for the CP.
Finally, based on the theoretical considerations and the discussion of the empirical research, I will draw some conclusions about the types of data that could provide evidence for the CPH.
Definition of the critical period for language acquisition
After completion of MF, the learning opportunity often remains but is usually significantly reduced and the learning outcome becomes more unpredictable. Attainment as a native is not possible if the first exposure to the language occurred after the closure of the CP (Eubank & Gregg, 1999). There is no agreement on the underlying mechanisms that may bring about the end of CP, but it is generally thought to be the result of neurological or cognitive maturation.
In the next section, I will provide an overview of different explanations for CP, and also discuss whether some affective accounts of age-related differences in SLA can be considered as possible explanations for CP.
Causes of the critical period
- Neurobiological explanations
- Cognitive approaches
- Piagetian explanations
- The Fundamental Difference Hypothesis
- Affective explanations
- Summary of the different proposals
It is also worth mentioning that the explanations based on Piaget's theory are not completely independent of those approaches that consider the CP as the result of neurological changes since Piaget related the emergence of the formal operation stage to neurological maturation (Singleton, 1989). In his discussion of the CPH, Krashen (1975, as cited in Singleton, 1989) concentrates on the prevalence of abstract thinking and the "general tendency of adolescents to construct theories" (Inhelder & Piaget, 1958, as cited in Singleton, 1989, p. 181), which are considered to be characteristics of the formal operation stage. From this perspective, the end of access to the language learning device would be equivalent to the closure of the CP.
The end of the CP means the loss of this ability, and adults must employ explicit problem-solving abilities to compensate for this loss. Some reviewers of the CPH, such as Singleton (2007), interpret certain affective explanations for the differences between children and adult language learners as possible explanations for the CP. Singleton cites, for example, Guiora's (1972, as cited in Singleton, 2007) theory of the language ego and Schumann's (1975, as cited in Singleton, 2007) interpretation of age-related differences as the result of the increasing social and psychological distance between the adult learner and the target language group.
Affective theories should therefore not be considered as explanations for CP, as they predict that language learning ability is affected differently by aging as in the case of the existence of a CP. To summarize, researchers have widely differing views on the causes of CP. Proponents of the cognitive explanations also disagree about the exact nature of the mechanisms that may inhibit language acquisition.
Furthermore, different theories have different implications for the extent and timing of CP. If we try to summarize the various proposals regarding the closure of KP, we will have a rather wide age range; CP for pronunciation ends somewhere between the ages of six and puberty, while the acquisition of grammar becomes more difficult between the onset of puberty and the age of thirty. These factors may lead to a number of controversies regarding the empirical testing of PHC and a lack of agreement on what data would constitute evidence for PHC.
In the next part of the paper, I will provide an overview of some important studies investigating the CPH with a focus on the controversial issues that arise in connection with the interpretation of their results from the point of view of the CPH.
Empirical research
- The Johnson and Newport (1989) study
- The criticism of Johnson and Newport (1989)
- The Birdsong and Molis (2001) study: The influence of the L1
- The question of native-like attainment
Johnson and Newport also suggested that the rule-type-difficulty differences are not simply the result of the influence of L1; therefore, these findings can also be interpreted as. Another criticism made by Bialystok (1997) raises an important issue related to the verification of CPH. However, it is possible to account for the age effects after maturation within the framework of CPH.
Thus, the fact that even in adulthood age has an effect on language learning outcome does not necessarily refute the CPH as it is consistent with certain formulations of the hypothesis. If we examine the graph containing Johnson and Newport's (1989) data reanalyzed by Bialystok and Hakuta (1994, as cited in Bialystok, 1997), we can discover this essential discontinuity; the slope of the curve showing performance on the grammatical judgment test changes around the age of eighteen. Since there is no agreed age for the closure of the CP for grammar, Johnson and Newport assumed that the cut-off age is related to puberty, which is the dividing line most often mentioned in the discussions about the CPH.
This later age is not incompatible with CPH, as, for example, the theory of Walsh and Diller (1981, as cited in Singleton, 1989) suggests that the ability to acquire L2 grammar may begin to decline around the age of twenty as a result of maturation. certain neurons. Unlike the Johnson and Newport study, there was no noticeable decline in performance between ages seven and fifteen, and participants generally scored higher than the Chinese and Japanese subjects. I have already mentioned that the occurrence of a discontinuity in performance around the ripening point is crucial for the verification of CPH, as this is one of the defining characteristics of CP.
Molis (2001) is also characterized by this important discontinuity; the slope of the regression line changes around age seventeen. I have already argued that a decline with increasing age after the conclusion of the CP is not necessarily problematic for the CPH. However, in the case of Birdsong and Molis's (2001) study, the negative relationship between age and performance after puberty is significantly stronger than that obtained by Johnson and Newport's (1989) reanalysis in Bialystok and Hakuta (1994, as cited) . in Białystok, 1997).
The results of some studies investigating the special characteristics of exceptional students also suggest that the refutation of the CPH is not as simple as it was suggested by Long.
Conclusion
Since the explanations that consider affective factors to be the cause of the age-related differences do not necessarily predict the existence of a CP, it must be demonstrated that the type of results described above cannot be explained by certain affective variables, and age as an indicator of maturational state should be the strongest predictor of performance. More evidence for CPH would be the lack of native-like attainment among those who started L2 learning after completing CP. Finally, as I argued in the Birdsong and Molis (2001) study, a pattern of age effects indicating the existence of a CP should be observed regardless of the languages studied.
Participants may generally achieve higher or lower proficiency depending on the proximity of L1 and L2, but the results should show characteristic features of CP, such as a discontinuity around the maturation point. The controversial issues discussed in this paper have additional implications for CPH testing. Disagreement regarding the interpretation of the lack of age effects on the acquisition of certain types of rules in Johnson and Newport (1989) and the lack of an age-related decline before puberty in the case of the Birdsong and Molis (2001) study indicated that a test measuring participants' L2 knowledge must be sufficiently rigorous and demanding.
Otherwise, the results regarding certain age groups or rule types could reflect ceiling effects rather than an effect of age, making the interpretation of the findings more problematic. In addition, some questions raised by Birdsong and Molis' (2001) study on the influence of L1 on L2 learning at different ages remain unanswered. In order to clarify these questions regarding the influence of L1, more research with different L1s and L2s should be conducted to investigate how combining languages modifies the effect of age on language performance, and the implications of the findings for CPH should be reviewed.
Finally, as far as the conflicting views on the characteristics of the CP are concerned, further research is needed on the nature of CPs in human development and on the processes that might underlie a CP for L2 acquisition to to increase our understanding of how age can influence L2 learning. Critical period effects in second language acquisition: The effect of written versus auditory material on the assessment of grammatical competence.
