在二语写作教学中如何设计任务？任务复杂度作为任务设计的重要维度和指标，对建立任务分级和排序标准具有重要意义。关于任务复杂度的假说主要有两种：一是Skehan和Foster等基于有限注意资源模型提出的竞争假说，一是以Robinson基于多元注意资源模型提出的认知假说，两种假说对任务复杂度影响二语产出的预测是不同的。此外，近年来合作研究在二语习得领域受到广泛关注。合作写作以社会建构主义理论和建构主义理论为基础，认为合作在二语写作中对学习者语言产出具有重要的作用和意义。本研究将任务复杂度与合作互动因素相结合，探究任务复杂度与合作互动对中级汉语水平二语者写作产出中句法复杂度和准确度的影响。

本研究从数量、多样性和精细性三个维度中选取了7个指标来测算不同任务下句法复杂度的差异，从汉字、词汇和语法三个方面测算准确度的变化，具体包括以下几个关键问题：（1）任务复杂度对汉语二语者写作产出的句法复杂度和准确度各个指标的影响如何？（2）合作互动对汉语二语者写作产出的句法复杂度和准确度各个指标的影响如何？（3）任务复杂度和合作互动在写作产出的句法复杂度和准确度各个指标上是否存在交互作用？

为解决上述问题，本研究采用2*2被试内被试间两因素混合实验设计，实验对象为32名中级汉语水平二语者，让他们在不同的任务下进行写作，然后对语料进行量化分析。本文的基本分析单位是T单位，计算了句法复杂度和准确度各个指标的数据并进行了重复测量方差分析，随后根据录像和访谈对结果进行质性分析。此外，被试还需填写Robinson的任务感知量表，从难度、压力、兴趣、动机和能力五个方面进行自我评估，用以分析自我感知与不同任务类型的关系。

研究结果表明：（1）提高任务复杂度会降低汉语二语者写作产出的句法复杂度，对准确度影响甚微，在准确度各个指标上均不存在主效应。本研究结果支持了竞争假说。（2）合作互动对汉语二语者写作产出的句法复杂度影响较小，但是对准确度具有促进作用，在词汇准确度和语法准确度上主效应显著。（3）任务复杂度和合作互动在汉语二语者写作产出句法复杂度和准确度各个指标上不存在交互作用。（4）汉语二语学习者更喜欢任务复杂度较低的写作，合作写作更受汉语二语学习者的欢迎。合作能够降低写作焦虑，提升写作兴趣。

How to design tasks in second language writing teaching? Task complexity, as an important dimension and indicator of task design, is of great significance for establishing task classification and sorting standards. There are two main hypotheses about task complexity: one is the competing hypothesis proposed by Skehan and Foster based on the limited attention resource model, and the other is the cognitive hypothesis proposed by Robinson based on the multi-attention resource model. The two hypotheses predict that task complexity affects L2 output differently. In addition, collaborative research has received extensive attention in the field of second language acquisition in recent years. Cooperative writing is based on social constructivist theory and constructivist theory, and believes that cooperation in second language writing plays an important role and significance in learners' language production. In this study, task complexity and cooperative interaction factors were combined to explore the effects of task complexity and cooperative interaction on the syntactic complexity and accuracy of Chinese L2 learners' writing production.

In this study, seven indicators were selected from three dimensions of quantity, diversity and sophistication to measure the differences in syntactic complexity under different tasks, and the changes in accuracy were measured from three aspects of Chinese characters, vocabulary and grammar. This research specifically includes the following key questions: (1) What is the impact of task complexity on the syntactic complexity and accuracy of Chinese L2 learners' writing production? (2) What is the impact of cooperative interaction on the various indicators of syntactic complexity and accuracy of Chinese second language learners' writing production? (3) Is there an interaction between task complexity and cooperation or not on the syntactic complexity and accuracy of writing production?

In order to solve the above problems, this study adopts a 2*2 within-subject and between-subject two-factor mixed experimental design. The experimental subjects are 32 Chinese second-language speakers, who are asked to write under different tasks, and then quantitatively analyze the corpus. The basic unit of analysis in this paper is the T-unit. The data of each index of syntactic complexity and accuracy are calculated and repeated measures ANOVA is performed, followed by a qualitative analysis of the results based on video recordings and interviews. In addition, the subjects were also required to fill in the Robinson task perception scale, and self-assessed from five aspects of difficulty, stress, interest, motivation and ability to analyze the relationship between self-perception and different task types.