Talking It Through: Peer Dialogue May Break Grammar’s Fixed Learning Sequence

For nearly four decades, one of the most influential ideas in second language research has been that grammar develops along a fixed, stage-like route that teaching cannot accelerate. According to Processability Theory and the Teachability Hypothesis, learners can only acquire a grammatical structure when they are psychologically ready for it, and instruction aimed at structures beyond a learner’s current stage is essentially wasted effort. A new study from Shiraz University in Iran now challenges that orthodoxy, presenting experimental evidence that carefully scaffolded peer dialogue can lift learners past developmental constraints that were long assumed to be immovable.

The research, conducted by Hossein Kargar Behbahani and Naser Rashidi of the Department of Foreign Languages and Linguistics at Shiraz University and published in SN Social Sciences, focused on one of the trickier structures in English: tag questions. These short interrogative attachments, such as “isn’t it?” or “didn’t they?”, demand that speakers simultaneously hold the tense, auxiliary, and polarity of the main clause in mind and invert them correctly. Because tag questions sit late in the hypothesized developmental sequence, they are an ideal testing ground for asking whether the sequence itself can be compressed.

Instead of framing the study within the psycholinguistic tradition that produced Processability Theory, the researchers drew on two very different theoretical foundations. The first was Vygotskian Sociocultural Theory, which treats learning as a socially mediated process in which knowledge is first constructed between people and only later internalized by the individual. The second was Complex Dynamic Systems Theory, which views language development as emergent, nonlinear, and sensitive to contextual and ecological nuances rather than marching through predetermined stages. These frameworks predict that the right kind of collaborative interaction, calibrated to a learner’s Zone of Proximal Development, the space between what a learner can do alone and what they can do with assistance, should be able to reshape developmental trajectories.

Methodologically, the team employed a Solomon Three-Group Design, a rigorous experimental arrangement that includes groups receiving treatment with and without pretests, plus a control group, allowing the researchers to separate genuine treatment effects from artifacts of testing itself. Participants were classified according to their cognitive style along the field dependence and field independence continuum, a dimension describing whether learners tend to perceive information holistically, relying on the surrounding context, or analytically, separating details from their background. This individual-difference variable has long been suspected of influencing how learners benefit from different instructional styles, and the study set out to determine whether it would moderate the effects of collaborative dialogue.

The treatment itself consisted of scaffolded collaborative dialogues, in which learners worked together on grammatical problems while receiving support geared to their individual Zones of Proximal Development. In this Vygotskian arrangement, assistance is not a fixed script but a dynamic negotiation: more capable peers or prompts provide just enough support to enable performance that would otherwise be impossible, and that support is gradually withdrawn as competence emerges. The idea of collective scaffolding, in which a group jointly constructs knowledge none of its members could produce alone, was central to the intervention. Learners talked their way through tag question formation, noticing gaps in their own and each other’s knowledge and co-constructing correct forms in real time.

The statistical analysis, conducted with SPSS version 20 using t-tests, analyses of variance, and Scheffe post-hoc tests, produced results with real theoretical weight. Learners who received the scaffolded collaborative dialogue treatment showed both short-term and durable gains in tag question acquisition, effectively moving beyond the developmental constraints that Processability Theory predicts should hold them in place. In other words, instruction did not merely help learners perform better on structures already within reach; it appeared to accelerate development itself, propelling learners toward structures that the staged account says should remain out of bounds.

The findings on cognitive style were more surprising still. Field-independent learners, who tend to process language analytically, did outperform their field-dependent peers after the treatment, but the difference never reached statistical significance. The authors interpret this null result as evidence that, at least for the acquisition of tag questions, grammar development is predominantly a socially mediated process. When the engine of learning is collaborative dialogue rather than solitary analytical processing, the cognitive style a learner brings to the table may matter far less than the quality of the interaction itself. That would be good news for classrooms, where learners cannot be sorted by cognitive style and instruction must work for everyone.

Taken together, the results pose a direct challenge to the assumptions of Processability Theory and the Teachability Hypothesis. If a staged, biologically constrained sequence governed grammar learning, scaffolded dialogue should not have been able to uplift developmental constraints in the way the study documented. The authors argue that their findings instead showcase language development as an emergent, dynamic, nonlinear process shaped by ecological nuances, consistent with Complex Dynamic Systems Theory. In such a view, developmental trajectories are not railroad tracks but weather systems: sensitive to initial conditions, responsive to intervention, and capable of sudden reorganization when the right conditions converge.

The study carries practical implications for teachers, curriculum designers, and teacher educators. If grammar can be learned out of sequence through appropriately scaffolded peer interaction, then syllabuses built strictly around developmental readiness may be unnecessarily restrictive. Pairing learners in structured collaborative tasks, training them to notice and repair each other’s grammatical errors, and calibrating support to each learner’s Zone of Proximal Development could offer a powerful complement to traditional form-focused instruction. The finding that field-dependent and field-independent learners benefited comparably suggests such approaches need not be tailored to cognitive style, simplifying implementation in mixed-ability classrooms.

The research also adds to a growing body of work questioning rigid stage models across second language acquisition research, from early morpheme-order studies to contemporary processability experiments. While the study examined a single structure, tag questions, within one instructional context, its Solomon Three-Group Design and durable outcome measures lend credibility to the central claim: that the developmental constraints on grammar learning are less like walls and more like doors, openable through the right kind of socially mediated effort. For a field that has long debated whether language is learned alone or together, the answer from Shiraz is emphatically together, and the implications for how grammar is taught worldwide could be considerable.

Subject of Research: The effects of scaffolded collaborative dialogue and field (in)dependence on second language grammar development

Article Title: The dynamic nature of grammar learning: a voyage into how scaffolded collaborative dialogue and field (In)dependence (Re)shape L2 grammar development

Article References: Behbahani, H. K., & Rashidi, N. (2026). The dynamic nature of grammar learning: a voyage into how scaffolded collaborative dialogue and field (In)dependence (Re)shape L2 grammar development. SN Social Sciences, 6(10), Article 535. https://doi.org/10.1007/s43545-026-01796-9

Image Credits: AI Generated

DOI: 10.1007/s43545-026-01796-9

Keywords: second language acquisition, grammar learning, scaffolded collaborative dialogue, Processability Theory, Teachability Hypothesis, Sociocultural Theory, Complex Dynamic Systems Theory, Zone of Proximal Development, field dependence, tag questions, peer interaction, cognitive style