This study aims to examine group trends and individual variability of descriptive Grammatical Complexity (GC) in writing development. A longitudinal sample of 41 high school EFL learners is followed for an academic year (12 waves of data collection), resulting in a corpus of 492 texts, coded for eight descriptive GC features of academic writing. Our analysis reveals different sets of descriptive GC features relevant to capturing group trends and individual variability in writing development. At the group level, two phrasal-level GC features could capture significant changes in group means over time; at the individual level, four types of clausal and phrasal GC features showed significant associations between individual variability over time (measured by Standard Deviation of differences) and gains (as measured by the increase of usage frequency). Findings are discussed with regard to modeling both inter-individual and intra-individual trajectories in writing development and pedagogical implications attuned to both group and individual needs.

中文翻译：

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写作发展中的群体趋势和个体差异：描述性语法复杂性分析

本研究旨在探讨写作发展中描述性语法复杂性（GC）的群体趋势和个体差异。我们对 41 名高中 EFL 学习者进行了一个学年的纵向样本跟踪（12 波数据收集），产生了包含 492 篇文本的语料库，针对学术写作的 8 个描述性 GC 特征进行了编码。我们的分析揭示了与捕捉写作发展中的群体趋势和个体差异相关的不同描述性 GC 特征集。在组级别，两个短语级别的 GC 特征可以捕获组平均值随时间的显着变化；在个体层面，四种类型的子句和短语 GC 特征显示出随时间变化的个体变异性（通过差异标准差来衡量）和收益（通过使用频率的增加来衡量）之间存在显着关联。