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Systematicity

Systematicity in SLA refers to the observation that learner language — the variety of the target language produced by second language learners (also called interlanguage) — is not random. Despite being neither the learner’s L1 nor the target L2, learner language at any given stage follows consistent, rule-governed patterns. Learners make predictable errors at predictable stages; developmental sequences (the order in which linguistic features are acquired) are remarkably consistent across learners from different L1 backgrounds; and learners apply their own systematic, if not targetlike, rules to produce novel utterances. Systematicity is one of the key properties establishing that learner language constitutes a genuine linguistic system, not simply a chaotic mixture of L1 influence and random guessing.

In-Depth Explanation

Systematicity as a property of interlanguage:

Larry Selinker (1972), who coined the term “interlanguage,” specified multiple properties of learner language, of which systematicity is central. Learner language is:

  1. Systematic: Rule-governed, predictable, internally consistent at each stage
  2. Variable: Not entirely consistent — learners show variation across contexts and communicative demands
  3. Dynamic: Systematically changing over time as acquisition progresses
  4. Fossilizable: Sometimes stabilizing at a non-targetlike stage (fossilization)

The systematicity property means that learner mistakes are not random errors but reflections of underlying rule systems — often rules that are:

  • Simplifications of target language rules (overgeneralization)
  • Transfer from the L1
  • Universal developmental preferences (e.g., preferring open syllables over closed)

Developmental sequences:

The strongest evidence for systematicity in SLA is the finding of consistent developmental sequences — fixed orders in which grammatical features are acquired — that recur across learners regardless of L1.

Key documented sequences:

  • English morpheme order (Dulay & Burt, 1974; Krashen’s natural order): -ing, plural -s, copula be, auxiliary be, article, irregular past, regular past -ed, third person singular -s, possessive -s acquired in approximately this order by L1 Chinese and L1 Spanish learners of English — despite very different L1 grammars.
  • Negation in English: Learners pass through: (1) “No + utterance” → (2) “No/not + verb” → (3) Auxiliary + negation → (4) Analyzed auxiliary + negation — regardless of L1.
  • Question formation in English: Similar staged developmental sequence across L1 backgrounds.

These sequences suggest that SLA is governed partly by universal cognitive and linguistic factors that override L1 influence.

Systematicity vs. variability:

Systematicity does not mean learners are 100% consistent. Variable use of a form (using both the correct and incorrect version, depending on context, interlocutor, and attention) is normal. The key insight is that variability itself is systematic — learners are more accurate in careful, planned production than in spontaneous conversation; more accurate on linguistic features that are perceptually salient; more accurate in contexts that do not overload cognitive resources.

Implications for instruction:

Systematicity implies that:

  • Instruction cannot simply “implant” any linguistic feature at any time — features emerge when the learner’s developmental stage is ready for them.
  • Error correction of features learners are not developmentally ready for may produce temporary correction in controlled conditions but will not advance acquisition.
  • Instructional sequences should ideally align with developmental sequences — teaching features in the order they are naturally acquired.

History

The concept of interlanguage systematicity developed primarily through Selinker’s foundational 1972 paper and the morpheme order studies of the early 1970s (Dulay & Burt; Bailey, Madden & Krashen). The natural order and developmental sequence findings contributed to Krashen’s influential Input Hypothesis framework. The Teachability Hypothesis (Pienemann, 1984, 1998) formalized the relationship between developmental stages and instructional effectiveness, predicting that instruction is effective only when it targets the next stage in the developmental sequence.

Common Misconceptions

  • “Learner errors are just mistakes — random and meaningless.” Errors are systematically rule-governed and linguistically informative about the learner’s current interlanguage stage.
  • “Correcting every error will fix systematicity issues.” If the error reflects a developmental stage, error correction may produce temporary local repair but will not advance the underlying system.
  • “Systematicity means all learners take exactly the same path.” Developmental sequences show the macro-level order; individual variation within each stage is expected.

Practical Application

  • Understanding that your errors are often systematic (not random) allows you to analyze what underlying rule your interlanguage is operating by. This is more useful than simply noting “I got it wrong.”
  • Some improvements will come in jumps at developmental transition points rather than gradual linear improvement. Plateaus in accuracy on a particular feature may precede a sudden jump when the system reorganizes.
  • Prioritize continued extensive input exposure — systematic advancement through developmental sequences correlates with input quantity.

Related Terms

Sources

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