生成式AI让大学生解题时间减少27%，但知识掌握反而下降25%。
Faster Completion, Less Learning: Generative AI Reduced Study Time on Math Problems and the Knowledge They Build
- 对比文本题与绘图题，发现易受AI影响的题目学习时间显著缩短
- 大学生成绩在无监考下正确率下降25%，有监考时差异消失
- 首次大样本证据显示生成式AI正导致学生认知依赖，影响真实学习
生成式AI如何改变学生的日常学习过程及其长期学习成效？自述调查显示变化不大，小规模行为研究虽发现广泛使用AI，却缺乏足够规模和时长来衡量学习后果。本研究利用覆盖十年、320万次ALEKS学习交互的面板数据，结合ALEKS PPL学业评估数据，通过准实验设计，比较对AI更敏感（文本型应用题）和较不敏感（互动绘图题）的任务。大学本科生在ChatGPT发布后，每季度学习时间减少2.8%，十一季度累计下降26.9%；高中生下降31.3%，初中生9.0%，五年级学生无明显变化。在监考条件下，这种时间差异完全消失，排除了效率提升的可能解释。对随机分配的监考保留题项的逻辑固定效应模型显示，正确作答概率下降25%；非监考评估则出现相反方向的大幅上升，无法用平台、群体或课程差异解释。这些结果是首批大规模行为与成效证据，表明生成式AI正在改变学生的学习方式与知识建构——体现为群体层面的“认知投降”现象，对教育研究、评估治理及AI政策具有直接意义。
原文摘要 · Abstract (English)
How much have students' ordinary learning processes shifted in response to generative AI, and how does that affect their durable learning outcomes? Self-report surveys show little change, while small-scale behavioral studies report widespread AI use without the scale or duration to measure learning consequences. We address both questions using a ten-year panel of $3.2$ million ALEKS learning interactions for investigating time-on-task, complemented by ALEKS PPL placement-assessment data for examining proctoring and learning outcomes, with a quasi-experimental design exploiting variation in tasks that are more susceptible to AI (text-based word problems) and less susceptible to AI (interactive graph-based problems). Learning time on AI-susceptible problems declines $2.8\%$ per quarter among college students after ChatGPT's release, cumulating to $26.9\%$ over eleven quarters; high-schoolers show $31.3\%$, middle-schoolers $9.0\%$, and Grade 5 students no detectable change. Among college students, the post-ChatGPT divergence vanishes entirely under proctoring, ruling out broad efficiency gains as the likely explanation. Logistic fixed-effects models on randomly assigned proctored retention items yield a $25\%$ cumulative decline in odds of correct response; the same estimator on non-proctored assessment produces a large opposite-signed increase -- inconsistent with any platform, cohort, or curriculum explanation. These results are among the first large-scale behavioral and outcome evidence that generative AI has altered how students study and the knowledge they build -- the population-level indicator of \emph{cognitive surrender}, with direct implications for educational research, assessment governance, and AI policy.
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