Plasticity, Variability and Age in Second Language Acquisition and Bilingualism

Abstract

Much of what is known about the outcome of second language acquisition and bilingualism can be summarized in terms of inter-individual variability, plasticity and age. The present review looks at variability and plasticity with respect to their underlying sources, and at age as a modulating factor in variability and plasticity. In this context we consider critical period effects vs. bilingualism effects, early and late bilingualism, nativelike and non-nativelike L2 attainment, cognitive aging, individual differences in learning, and linguistic dominance in bilingualism. Non-uniformity is an inherent characteristic of both early and late bilingualism. This review shows how plasticity and age connect with biological and experiential sources of variability, and underscores the value of research that reveals and explains variability. In these ways the review suggests how plasticity, variability and age conspire to frame fundamental research issues in L2 acquisition and bilingualism, and provides points of reference for discussion of the present Frontiers in Psychology Research Topic.

Keywords: age factors; bilingualism; critical period; dominance; individual differences; plasticity and learning; second language acquisition; variability.

FIGURE 1

Sequential, overlapping critical periods in infant speech perception development. Solid lines represent typical onsets and offsets; broken lines indicate extensions of periods. Adapted from Werker and Hensch (2015). Republished with permission from Annual Reviews.

FIGURE 2

Schematic representations of age of acquisition (AoA) effects on L2 attainment. (A) linear decline of L2 attainment over all AoA; (B) initial decline of L2 attainment followed by leveling off over subsequent AoA; (C) L2 attainment plateau, followed by decline, followed by leveling off over subsequent AoA; (D) L2 attainment plateau followed by decline over subsequent AoA.

FIGURE 3

Results of a test of English morphosyntax, as a function of age of arrival in the United States. (A) Shows overall percent correct for Korean native speakers (filled circles) and native English controls (open circles); (B) breaks out test results by grammatical items (top) and ungrammatical items (bottom); (C) depicts different functions for ungrammatical rule-based items vs. ungrammatical lexically-based items. Adapted from Flege et al. (1999). Republished with permission from Elsevier.

FIGURE 4

Performance on procedural and declarative memory tasks for Learners (L), Non-learners (N), and Simplifiers (S). Adapted from Ettlinger et al. (2014). Republished with permission from Cambridge University Press.

FIGURE 5

Representation of balanced bilingualism, showing that “balanced” only implies dominance in neither language, not high proficiency in both languages. Adapted from Goto Butler and Hakuta (2004). Republished with permission from John Wiley and Sons.

FIGURE 6

For Spanish-dominant and Catalan-dominant Majorcan bilinguals, Euclidean distances between same-speaker tokens of /e/-/ε/ and /o/-/ɔ/, plotted as a function of BLP scores, which range from –120 (strongest Spanish dominance) to +130 (strongest Catalan dominance). Adapted from Amengual (2014). Republished with permission from Sage Publishing.

FIGURE 7

Correlation of BLP scores with relative peak alignment scores for Spanish–K’ichee’ bilinguals from Cantel and Nahualá. Zero-upward BLP scores = increasing Spanish dominance. Zero-downward BLP scores = increasing K’ichee’ dominance. Relative peak alignment scores = duration from syllable onset to peak pitch divided by total duration of syllable; values are individual speaker averages. Adapted from Baird (2015). Republished with permission from Cambridge University Press.