Effects of Age on Second Language Acquisition

It is popularly believed that age plays a biological role in language acquisition. This belief is supported by the fact that babies can acquire their first language (L1) within five years (Ortega, 2009). After this initial period, language learners rarely achieve native like proficiency in a second language (L2), which has been accredited to what Penfield, Roberts, and later Lenneberg described as the critical period.

Researchers have looked for biological findings to support the critical period hypothesis. Penfield and Roberts found that there was a loss of plasticity in the brain by the age of nine and a completion of lateralization—performing a certain function, like processing language, in mainly one hemisphere of the brain—by puberty. Other studies have referred to the process of myelination, which allows information to quickly go between neurons, during the first 12 years of life as another contribution to the critical period (Ortega, 2009). Another argument for the critical period is the increase in estrogen or testosterone after puberty decreases one's language learning potential; however, there is not sufficient neurological or neurochemical evidence to clearly back up the critical period.

Even the learning rates of language learners seem to support the critical period. Krashen, Long, and Scarcella reviewed 23 L2 studies and concluded that older learners perform at higher rates at the beginning, yet over time younger learners will outperform them (Ortega, 2009). Further research has shown that learners older than seven processed syntactic features differently than L1 speakers but processed semantic features the same (Ortega, 2009). Bley-Vroman’s fundamental difference hypothesis claims that children have the natural ability to acquire L1 grammar but adults have lost this ability; therefore, adults rely on other skills like problem solving and consciously paying attention to form (Ortega, 2009). Despite these studies and findings, other findings and additional factors discredit age as a biological factor of L2 learning.

Some late L2 learners are extraordinarily successful in the second language despite their age. An example of this is the two cases of L2 Egyptian Arabic speakers: Julie, who acquired the language naturalistically, and Laura, who acquired it through an instructional manner (Marinova-Todd et al., 2000). Both reached high levels of proficiency in two distinct ways. If cases like theirs exist, the critical period cannot be a biological fact.

Further arguments against the critical period establish the difficulty to acquire a new language is not due to biological constraints but rather due to one's expertise and dominance in their L1. Ortega (2009) writes about Piske et al. 2001, who describe age as a marker of the L1 development, which, when it is more developed, will influence the L2 more. Another researcher Ortega (2009) cites is Flege, who explains that accents are due to one’s own strength in pronouncing his or her native language, not an inability to learn how to pronounce. Ortega (2009) reports of Osterhout’s research of how certain brain activation patterns can change in location and degree after a certain amount of exposure to the L2. A main argument against biological constraints is that older learners’ lives are drastically different from those of young learners’ and, therefore, they are effected by different socio-educational factors as well as motivation (Marinova-Todd et al., 2000). Language abilities will be different among learners that are consequences of other environmental factors and are not impossible to overcome because they are biological (Ortega, 2009).


The fundamental difference hypothesis has influenced the type of second language instruction according to the students age. Younger learners are generally taught more implicitly, and the rate of acquisition must be slowed down. Meanwhile, older learners are taught more explicit grammar that they can analyze and problem solve with at a faster pace. This general difference could be a reason why older learners are not as successful. I would be interested in studies that incorporate the same teaching methods to both populations as well as studies that include both populations in the same class. However, the latter may not be as plausible due to the cognitive development differences due to age, but alterations could be made that could lead to successful results where the older learners do not feel as if they are being treated as children. Aside from these possibilities, older learners have an array of responsibilities and other factors that distract and intervene in their L2 learning process. The instructor must provide different possibilities and options that can help different students work with the L2 along with these additional factors in their lives.