Mikey Does

Order of Acquisition

Order of acquisition (also called acquisition order) refers to the finding that second language learners acquire specific grammatical morphemes in a consistent, predictable sequence — and that this sequence is largely the same regardless of the learner’s first language. A Chinese L1 learner of English and a Spanish L1 learner acquire the same morphemes in approximately the same order, even though their native languages differ dramatically. This finding, first documented in the 1970s, challenged behaviorist models of language learning and became one of the most cited results in SLA research.

Also known as: morpheme acquisition order, natural acquisition order, acquisition sequence

In-Depth Explanation

The order of acquisition was established through the morpheme studies of the 1970s. Heidi Dulay and Marina Burt (1974) administered the Bilingual Syntax Measure to children from Chinese- and Spanish-speaking backgrounds learning English as a second language. Analyzing the accuracy of eight English morphemes in spontaneous speech, they found that both groups acquired the morphemes in nearly identical order — an order that correlated poorly with the frequency of those morphemes in classroom input or with the order in which they were taught.

The eight morphemes studied (and their approximate acquisition order, from earlier to later acquired) included:

  1. Progressive -ing (e.g., “she is running”)
  2. Plural -s (e.g., “two cats”)
  3. Copula be contracted (e.g., “he’s tall”)
  4. Auxiliary be contracted (e.g., “she’s running”)
  5. Articles (a, the)
  6. Irregular past (e.g., “went,” “came”)
  7. Regular past -ed (e.g., “walked”)
  8. Third person singular -s (e.g., “she walks”)

This research built on Roger Brown’s landmark L1 acquisition study (1973), which documented a similar consistent order for English-speaking children acquiring their first language — though the L1 and L2 orders are not identical.

The order of acquisition finding had several significant implications. First, it suggested that the sequence of acquisition is driven by internal psycholinguistic factors — perhaps the perceptual saliency, semantic complexity, or structural regularity of morphemes — rather than by instruction, frequency of input, or L1 transfer. A morpheme like third-person singular -s is highly frequent in English input and explicitly taught early in most curricula, yet it is acquired late — learners persist with errors like “she walk” far into intermediate stages.

Second, the consistent order across L1 backgrounds supported the existence of a language acquisition mechanism that processes L2 input systematically, rather than simply mapping L2 onto L1 structures. This was used as evidence against an extreme transfer view of interlanguage and supported the idea that learners’ developing grammars follow a universal developmental trajectory.

Third, the finding highlighted the relationship between accuracy in controlled tasks and genuine acquisition. Dulay and Burt used accuracy order (the proportion of obligatory contexts where a morpheme is supplied correctly) as a proxy for acquisition order. Critics later noted that accuracy in elicited tasks may not perfectly reflect acquisition — learners can use morphemes correctly in one context and fail in another — leading to debate about what the morpheme studies were actually measuring.

History

The morpheme studies emerged against the backdrop of 1970s debates between behaviorist (habit formation through L1 transfer and imitation) and mentalist (innatist, Chomskyan) accounts of language learning. Dulay and Burt’s work was part of a cluster of studies — alongside Roger Brown’s L1 research and Krashen’s synthesis — that reframed SLA as a developmental, rule-governed process rather than a habit-formation process shaped primarily by L1 interference.

Krashen incorporated the order of acquisition into his natural order hypothesis, one of the five elements of his Input Hypothesis model. He argued that the consistent order was evidence that acquisition is a natural, predictable process governed by comprehensible input, not by teaching sequences.

Later research complicated the picture. Subsequent morpheme studies using different tasks, learner populations, and languages found variation in the ordering, suggesting that the order is a robust trend but not an invariant law. Researchers including Goldschneider and DeKeyser (2001) conducted meta-analyses showing that the acquisition order correlates with a cluster of factors: perceptual saliency, semantic complexity, morphophonological regularity, syntactic category, and frequency. This multi-factor account replaced the idea of a single universal order with a more nuanced probabilistic model.

Common Misconceptions

  • “The acquisition order is the teaching order.” Teachers cannot override the acquisition sequence by presenting morphemes in a different order. Learners acquire late-acquired morphemes (like third-person -s) when they are developmentally ready, regardless of how much instruction they receive. This is known as the teachability constraint, formalized in Manfred Pienemann’s developmental sequence research.
  • “Acquisition order means learners can’t produce a morpheme before its slot in the sequence.” Learners can produce morphemes before acquiring them systematically — often by memorizing formulas. “She walks to school” might appear early as a chunk, not evidence of acquired third-person -s.
  • “The order is the same in all languages.” The specific morpheme orders documented are for English. Other languages have their own acquisition orders, shaped by the structural features of those languages. Japanese morpheme acquisition research, for example, documents a different sequence reflecting Japanese morphology.
  • “High accuracy means full acquisition.” A learner might score 90% accuracy on a cloze test for progressive -ing but still not have acquired it as a productive rule — they may be treating common verb phrases as memorized units.

Criticisms

The morpheme studies have faced sustained methodological criticism. The most significant concern is that accuracy in obligatory contexts is a blunt measure: it collapses form-function pairings, conflates different types of errors (avoidance, misformation, omission), and does not distinguish proceduralized knowledge from declarative knowledge.

Later researchers, particularly those working in implicit learning and explicit knowledge frameworks, have argued that what the morpheme studies measured is accuracy under relatively unspontaneous elicited production conditions — not acquisition in the sense of a stable underlying grammar. Controlled studies using primed production tasks and eye-tracking have produced somewhat different acquisition sequences, raising questions about whether the classic order reflects something about morphemes or something about how the Bilingual Syntax Measure elicits data.

Despite these critiques, the core finding — that L2 acquisition is not a random process and shows systematic developmental patterns — has been replicated enough times, in enough languages and populations, to be considered a foundational result of SLA research.

Social Media Sentiment

The order of acquisition comes up in language learning communities primarily as a source of frustration. On r/languagelearning and r/LearnJapanese, learners frequently report that despite extensive study of a particular form, errors persist — which is consistent with what the research predicts. The inability to reliably produce Japanese verb te-forms even after months of drilling is a classic example of a form that takes longer to acquire than instruction alone would suggest. When the concept is explained in online forums, it is often a revelation — “so there’s actually research showing this isn’t just me being bad” is a common response. On YouTube, creators covering SLA theory regularly cite the morpheme studies as evidence for immersion-based approaches.

Last updated: 2026-04

Practical Application

The order of acquisition research has concrete implications for how language learners approach grammar study:

  • Instruction isn’t wasted, but it’s not sufficient. You can teach — and explicitly learn — a grammatical form before you’re developmentally ready to acquire it. This doesn’t mean not studying grammar; it means expecting that accuracy under pressure takes longer than accuracy in controlled practice.
  • Errors on late-acquired forms are normal, not a sign of failure. Third-person singular -s is the last-acquired morpheme in the classic English sequence — so even advanced L2 English speakers make errors on it in spontaneous speech. In Japanese, verb conjugation errors persist well into advanced stages. This is expected, not a deficiency.
  • Focus on meaning first, form second. The research suggests morpheme acquisition follows a natural sequence driven by meaningful input. Spending the most study time on morphemes the research shows are acquired late (trying to “force” acquisition) is less effective than ensuring rich, comprehensible implicit learning opportunities alongside targeted form-focused instruction.
  • Track accuracy over time, not in single sessions. Because accuracy fluctuates based on task type and attention, you need evidence from multiple contexts — spontaneous writing, monitored speaking, unmonitored conversation — to know whether a form has been acquired, not just learned explicitly.

Related Terms

See Also

Sources

mikeydoes.com