Picture description (PD) tasks are widely used in second language (L2) teaching, research, and assessment to elicit and/or evaluate L2 learners’ writing performance. However, there is little research on the effects of the characteristics of such tasks on L2 writing performance. This study aimed to examine the effects of task difficulty and learner variables on the linguistic characteristics of responses to the 2020 version of the Duolingo English Test (DET) PD writing tasks. The written responses of 1439 test takers from four first language (L1) backgrounds and at different levels of L2 proficiency to 335 DET PD tasks at two levels of difficulty were analyzed and compared in terms of measures of fluency, accuracy, and complexity using various computer programs. The findings indicated that task difficulty did not affect writing performance significantly; high-proficiency learners tended to perform better than did their low-proficiency counterparts; responses receiving higher scores tended to be longer and more accurate; and learner L1 was significantly associated with writing grades and linguistic features. The findings and their implications for the DET PD task and the DET validity argument are discussed.

中文翻译：

---

探索任务难度和学习者变量对图片描述写作任务表现的影响

图片描述 (PD) 任务广泛应用于第二语言 (L2) 教学、研究和评估中，以引发和/或评估 L2 学习者的写作表现。然而，关于此类任务的特征对二语写作表现的影响的研究却很少。本研究旨在探讨任务难度和学习者变量对 2020 版 Duolingo 英语测试 (DET) PD 写作任务反应的语言特征的影响。使用各种计算机对来自四种第一语言 (L1) 背景和不同 L2 熟练程度的 1439 名考生对 335 项两个难度级别的 DET PD 任务的书面反应进行了分析和比较，包括流畅性、准确性和复杂性程式。研究结果表明，任务难度并没有显着影响写作表现；高水平的学习者往往比低水平的学习者表现得更好；得分较高的回答往往更长、更准确；学习者的 L1 水平与写作成绩和语言特征显着相关。讨论了这些发现及其对 DET PD 任务和 DET 有效性论证的影响。