Definition:
Developmental sequences in second language acquisition refer to the consistent, predictable orders in which learners acquire specific linguistic structures, regardless of their native language, the target language, the instructional method, or the sequence in which structures are explicitly taught. Research across typologically diverse L1–L2 pairs has demonstrated that certain grammatical forms are acquired in a fixed order relative to each other — for example, learners of English as an L2 reliably acquire the progressive -ing before the regular past -ed, and acquire the third-person singular -s very late relative to other morphemes. These sequences represent strong evidence that SLA follows internal psycholinguistic processes, not merely the curriculum or the learner’s mother tongue.
Also known as: Acquisition orders, developmental stages, morpheme order, acquisitional sequences
In-Depth Explanation
The morpheme order studies.
The modern study of developmental sequences began with Roger Brown’s (1973) longitudinal study of L1 acquisition, which found that three English-speaking children acquired 14 grammatical morphemes in a remarkably consistent order. Dulay and Burt (1973, 1974) then replicated this finding cross-sectionally with L2 learners of English — Spanish- and Chinese-speaking children acquiring English as an L2 showed a similar (though not identical) morpheme acquisition order. Krashen later incorporated this finding into his Natural Order Hypothesis, arguing that the acquisition order reflects the natural operation of the language acquisition device, not instruction.
The finding was striking: the order in which morphemes were taught in the classroom had little effect on the order in which they were acquired.
Developmental stages vs. morpheme order.
The morpheme order studies (cross-sectional, comparing learners at different proficiency levels) are sometimes conflated with developmental stage research (longitudinal, tracking individual learners over time). Both reveal systematic sequences, but with different granularity:
- Morpheme order: A rank-ordering of when specific morphemes reach 90% accurate production in obligatory contexts — a snapshot of relative difficulty.
- Developmental stages: A sequence of qualitatively distinct stages through which learners pass — each stage characterized by distinct interlanguage rules.
The German word order example and Pienemann’s Processability Theory.
The most fully worked-out developmental stage research comes from work on German L2 acquisition. Clahsen, Meisel, and Pienemann (the ZISA project, late 1970s–80s) found that learners of German as a second language passed through six stages of word order development, in a fixed sequence that could not be skipped or reordered:
Stage 1: SVO (canonical order) — Ich trinke Kaffee.
Stage 2: Adverb preposing with no reordering — Manchmal ich trinke Kaffee.
Stage 3: Verb separation (separable particles) — Ich mache die Tür auf.
Stage 4: Adverb preposing with inversion (subject-verb inversion) — Manchmal trinke ich Kaffee.
Stage 5: V-end in subordinate clauses — Ich weiß, dass er Kaffee trinkt.
Stage 6: Verb second with complex NPs — full target-like word order
No learner skipped a stage. Instruction could not push a learner directly from Stage 2 to Stage 5.
Manfred Pienemann then formalized an explanation in Processability Theory (1998): learners can only acquire structures that do not exceed their current processing capacity — the ability of the parsing/production system to exchange grammatical information between constituents. Each stage requires a new type of processing procedure, and these procedures must be acquired in a fixed order because higher procedures presuppose lower ones.
Pienemann’s Teachability Hypothesis (1984) applies developmental stage research to pedagogy: instruction can only promote acquisition of structures the learner is developmentally ready to acquire. Teaching a structure from two stages ahead will not cause acquisition — the learner will not retain it. Teaching a structure at the next developmental stage (i+1 in Krashen’s terms) may accelerate acquisition of that stage.
This has major implications for syllabus design: a purely structural syllabus that teaches grammar in order of “logical simplicity” or “frequency” may systematically mismatch the learner’s acquisitional readiness.
Japanese developmental sequences.
Japanese L2 acquisition research has documented developmental stages for several structures:
- Relative clauses: Learners pass through stages from unmarked object-modifying relative clauses to more complex subject-modifying and internally-headed relative clauses in a consistent order.
- Verb morphology: Acquisition of verbal inflections follows predictable patterns — present/non-past forms before past forms; polite (masu) forms often acquired before plain forms in instructed learners, but plain forms may be needed for natural reading comprehension before they reach accuracy in production.
- Particles: Topic marker ? and object marker ? are acquired in somewhat different trajectories; learners frequently omit or substitute particles in predictable ways at early stages.
- Negation: Sentence-final negation (??/???) before mid-sentence negation; learners tend to negate at the clause boundary before acquiring more structurally embedded negation.
Implications for self-directed learners.
Understanding developmental sequences suggests:
- Some grammatical “fossils” or persistent errors reflect stage-appropriate interlanguage, not carelessness — they will resolve as processing capacity develops.
- Drilling structures far ahead of the learner’s current developmental stage produces limited retention.
- Comprehensible input at i+1 — slightly beyond the learner’s current stage — provides the optimal acquisitional conditions per Krashen’s Input Hypothesis.
- Extensive, stage-appropriate input exposure (graded readers, listening at appropriate level) facilitates developmental progress more reliably than structural drilling alone.
Common Misconceptions
Misconception: Teaching a structure means it will be acquired.
Developmental sequence research consistently shows that explicit instruction does not override acquisitional readiness. Learners can learn to produce a structure under controlled test conditions without acquiring it — it may not generalize to free production and may be subsequently “lost” when under communicative pressure.
Misconception: Developmental sequences only apply to morphology.
While morpheme order studies are the most famous, developmental sequences have been documented for syntax (relative clauses, negation, interrogatives, word order), phonology (L2 phoneme acquisition stages), and vocabulary (depth of lexical knowledge development is also staged).
History
- 1973: Roger Brown publishes A First Language — documents consistent morpheme acquisition order in L1 English learners.
- 1973–74: Dulay & Burt demonstrate a similar (though distinct) acquisition order for L2 English learners — the “creative construction” hypothesis.
- 1977–83: ZISA project (Clahsen, Meisel, Pienemann) documents six-stage German word order developmental sequence for L2 learners.
- 1984: Pienemann publishes the Teachability Hypothesis — pedagogical implications of developmental sequences.
- 1998: Pienemann publishes Language Processing and Second Language Development: Processability Theory — the full theoretical account of why developmental sequences exist.
- 2000s–present: Processability Theory applied to Japanese, Arabic, Swedish, and other languages; debate continues about the universality of sequences and the extent to which they can be influenced by instruction.
Criticisms
Research on developmental sequences has been criticized for over-reliance on data from English L2 acquisition and a small set of morphosyntactic features — particularly English morpheme acquisition order studies and the German word order acquisition sequence. Generalizability to other target languages, less-studied L1-L2 combinations, and non-morphosyntactic features (pragmatics, lexical development, phonology) is far from clear. The claim that developmental sequences are invariant and cannot be altered by instruction has been partially revised: while sequences cannot be skipped wholesale, instruction appears to affect the rate of movement through stages and the robustness of forms at each stage. Methodological critiques include over-reliance on single production tasks and group-level data that may obscure significant individual variation.
Social Media Sentiment
Developmental sequences are discussed in applied linguistics and language teacher education communities, though they rarely surface in general language learning discussions. The practical implication — that certain grammatical structures are learned before others regardless of instruction order — is relevant for curriculum design but abstract for individual learners. Teachers encounter the concept when students “cannot” learn a form they have been taught repeatedly, which is often attributable to developmental prerequisite structures not yet being acquired. The teachability hypothesis (Pienemann) — that instruction only accelerates learning when the learner is developmentally ready — resonates with teachers who observe the phenomenon even without knowing the formal theory.
Last updated: 2026-04
Practical Application
Understanding developmental sequences helps language teachers and learners set realistic expectations about the order in which complex structures will be acquired, and avoid over-attributing slow progress to insufficient teaching or effort. Instruction can accelerate movement through developmental sequences when it is well-timed to a learner’s current developmental stage — but cannot shortcut the sequence entirely. For L2 Japanese learners, awareness of acquisition sequence research suggests prioritizing forms shown to develop earlier (e.g., te-form constructions, basic noun modification) before more complex structures like conditional forms or causative-passive combinations. Sakubo naturally exposes learners to vocabulary at levels matched to their current proficiency, supporting the input conditions that facilitate developmental progression.
Related Terms
See Also
Research
1. Brown, R. (1973). A First Language: The Early Stages. Cambridge, MA: Harvard University Press.
The foundational study documenting consistent morpheme acquisition order in three L1 English-acquiring children. Established the idea that language acquisition follows internal developmental sequences rather than being directly shaped by input frequency or parental instruction — setting the stage for the L2 morpheme order studies.
2. Dulay, H., & Burt, M. (1974). Natural sequences in child second language acquisition. Language Learning, 24, 37–53.
The landmark L2 morpheme order study demonstrating that Spanish- and Chinese-speaking children acquiring English L2 show a remarkably similar morpheme acquisition order — and that this order differs from both the L1 English order and from classroom instruction sequences. One of the most cited and debated findings in SLA history.
3. Pienemann, M. (1984). Psychological constraints on the teachability of languages. Studies in Second Language Acquisition, 6, 186–214.
The Teachability Hypothesis paper: argues on the basis of developmental stage research that explicit instruction can only advance acquisition when the learner is developmentally ready for the target structure. Structures beyond the learner’s current processing stage cannot be acquired through instruction alone, regardless of input or practice.
4. Pienemann, M. (1998). Language Processing and Second Language Development: Processability Theory. Amsterdam: John Benjamins.
Full theoretical statement of Processability Theory — the most complete explanation of why developmental sequences exist (each stage requires new processing procedures that build on prior procedures in a hierarchical order). Required reading for understanding the cognitive basis of acquisitional sequences.
5. Kawaguchi, S. (2005). Argument structure and syntactic development in Japanese as a second language. In M. Pienemann (Ed.), Cross-Linguistic Aspects of Processability Theory.
Applies Processability Theory to Japanese L2 acquisition, documenting developmental stages for Japanese argument structure and verb morphology. Demonstrates that the hierarchical processing requirements of Processability Theory correctly predict the order in which Japanese grammatical features are acquired — extending the theory beyond European language pairs.