Robert DeKeyser

Definition:

Robert DeKeyser is an American applied linguist and cognitive psychologist specializing in the cognitive mechanisms of second language acquisition, particularly the role of explicit instruction, procedural learning, and language aptitude. His most influential contribution is the application of skill acquisition theory — a framework from cognitive psychology — to explain how explicit L2 grammatical knowledge becomes automatized implicit competence through practice. DeKeyser has also made major contributions to adult language aptitude research and to the debate about whether adult L2 learners remain capable of achieving native-like implicit linguistic competence. His work positions him as one of the primary theoretical counterweights to Krashen’s non-interface position.

Institution: University of Maryland (Professor of Second Language Acquisition)

In-Depth Explanation

Skill acquisition theory in SLA.

DeKeyser’s central contribution is adapting Anderson’s (1983) ACT* (Adaptive Control of Thought) framework from cognitive psychology to SLA. Skill acquisition theory distinguishes three stages of skill development:

1. Declarative stage: The learner consciously knows a rule or fact but cannot yet execute it automatically. Example: a learner knows the rule “Japanese verb stems ending in -u take -tte in the te-form” and can state it but must consciously apply it during production.

1. Procedural stage: Through practice, the learner begins to compile the declarative knowledge into procedures — the rule begins to execute without requiring full conscious access.

1. Automatic stage: Through extensive practice, procedural knowledge becomes fully automatized — execution happens without conscious attention, at native-like speed, with minimal cognitive load. This is the implicit competence that characterizes fluent speakers.

DeKeyser’s key claim: this three-stage progression from declarative ? procedural ? automatic is available to adult L2 learners for grammatical knowledge. Explicit instruction builds declarative knowledge; communicative practice under appropriate conditions drives proceduralization and automatization. This is a direct challenge to Krashen’s non-interface position which holds that learned (explicit/declarative) knowledge never converts to acquired (implicit) competence.

The practice problem.

A key question in applying skill acquisition theory to SLA: what kind of practice drives proceduralization? DeKeyser argues for communicative practice — practice using target forms in meaningful, communicative contexts (not just drills for drill’s own sake):

• Drills (output practice without communicative purpose) may build speed of execution but fail to develop the contextualized, meaning-linked automaticity needed in real communication.
• Meaningful practice with target forms in communicative contexts (form-focused tasks, focused output practice) drives the form into automatic production in the conditions under which it must operate in real speech.

This is the SLA research basis for focus on form approaches — brief, reactive attention to form during primarily communicative activity provides the overlap of communicative and form-focused conditions needed for proceduralization.

The critical period revisited: aptitude and adult SLA.

DeKeyser has conducted important research on the Critical Period Hypothesis and adult language aptitude. His 2000 paper is particularly significant:

• Using the Johnson and Newport (1989) dataset on L1 Korean/Chinese immigrants to the US, DeKeyser reanalyzed outcomes and found that adult arrivals (post-puberty) who scored high on a verbal analytic ability test were able to achieve high grammaticality judgment scores.
• This suggests that for adult L2 learners with high language aptitude (specifically, high explicit/analytic ability), an alternative — explicit — learning mechanism may partly compensate for reduced access to the implicit acquisition mechanism available in childhood.
• This finding implies that adult SLA success is not impossible — it may require higher aptitude and more deliberate explicit learning effort to compensate for reduced implicit acquisition efficiency.

Language aptitude.

DeKeyser has extensively studied language aptitude — the cognitive abilities that predict L2 learning rate and ultimate attainment for adults:

• Classical aptitude measures (Carroll’s MLAT — Modern Language Aptitude Test) measure working memory, phonological discrimination, and inductive language learning ability.
• For explicit learning mechanisms: analytic ability (the ability to generalize rules from examples) is the key aptitude predictor for adult learners.
• For implicit learning mechanisms: more domain-general cognitive capacities (phonological memory, attention) predict implicit acquisition.

This work has practical implications for self-directed learners: understanding your aptitude profile can guide which learning strategies are most efficient for you.

Key Contributions

• Application of skill acquisition theory (declarative ? procedural ? automatic) to SLA
• Practice and automatization in instructed SLA
• Language aptitude research for adult learners
• Reanalysis of Critical Period data — explicit mechanism as adult compensation
• Integration of cognitive psychology with SLA theory

Selected Works

• DeKeyser, R.M. (1997). Beyond explicit rule learning: Automatizing second language morphosyntax. Studies in Second Language Acquisition, 19, 195–221.
• 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. (2007). Practice in a Second Language: Perspectives from Applied Linguistics and Cognitive Psychology. Cambridge: Cambridge University Press.
• DeKeyser, R.M. (2015). Skill acquisition theory. In B. VanPatten & J. Williams (Eds.), Theories in Second Language Acquisition. New York: Routledge.

Criticisms

DeKeyser’s skill acquisition theory has been challenged from multiple directions. Krashen-aligned researchers contest the fundamental premise that explicit knowledge converts to implicit competence through practice, arguing instead that the two knowledge systems are neurologically distinct and that explicit instruction produces only monitor-available knowledge that cannot become the basis for automatic, fluent production. The evidence that practiced explicit knowledge becomes implicit — rather than merely coexisting with separately developed implicit knowledge — remains contested.

The reanalysis of Johnson and Newport’s critical period data has been questioned on statistical and interpretive grounds. While DeKeyser demonstrated that high-aptitude adult learners can achieve native-like grammaticality judgment scores, critics note that grammaticality judgment tasks may tap explicit metalinguistic knowledge rather than the implicit competence that characterizes native speakers — meaning the reanalysis may show that high-aptitude adults can analyze grammar well, not that they have acquired it in the same sense as native speakers.

From a practical perspective, DeKeyser’s emphasis on “communicative practice that focuses on form” has been criticized as difficult to operationalize in real classroom settings. The specification that practice must be both communicatively meaningful and form-focused is theoretically precise but leaves teachers uncertain about concrete implementation — the gap between DeKeyser’s laboratory-demonstrated learning conditions and typical classroom constraints remains wide.

Related Terms

• Implicit vs Explicit Learning
• Acquisition-Learning Distinction
• Focus on Form
• Critical Period Hypothesis

See Also

• Rod Ellis
• Stephen Krashen
• Noticing Hypothesis
• Task-Based Language Teaching
• Sakubo

Research

• DeKeyser, R.M. (2007). Practice in a Second Language: Perspectives from Applied Linguistics and Cognitive Psychology. Cambridge University Press.
  Summary: The primary theoretical statement connecting cognitive psychology’s skill acquisition framework to SLA — examines how practice type, timing, and focus interact with learner aptitude to produce different acquisition outcomes.

• DeKeyser, R.M. (2000). The robustness of critical period effects in second language acquisition. Studies in Second Language Acquisition, 22(4), 499–533.
  Summary: The landmark reanalysis of Johnson and Newport’s critical period data, demonstrating that high-verbal-aptitude adults achieve native-like scores on grammaticality judgments — suggesting the critical period primarily constrains implicit learning, not overall attainment.

• Anderson, J.R. (1983). The Architecture of Cognition. Harvard University Press.
  Summary: The foundational ACT* (Adaptive Control of Thought) framework that DeKeyser applies to SLA — proposes the declarative → procedural → automatic knowledge transition that underpins skill acquisition theory’s predictions about language learning.

• DeKeyser, R.M. (2015). Skill acquisition theory. In B. VanPatten & J. Williams (Eds.), Theories in Second Language Acquisition (2nd ed., pp. 94–112). Routledge.
  Summary: DeKeyser’s own summary of how skill acquisition theory applies to SLA, including responses to major criticisms and updated evidence for the explicit-to-implicit conversion hypothesis.