Cheap and Fast – But is it Good? Evaluating Non-Expert Annotations for Natural Language Tasks
Rion SnowBrendan O'ConnorDaniel JurafskyAndrew Y. Ng
Demonstrates that carefully designed non-expert crowdsourcing can produce reliable NLP labels at a fraction of expert annotation cost.
Natural language processing research depends on large annotated datasets, but creating them with expert labelers is costly and slow. The article examines whether Amazon Mechanical Turk can supply reliable annotations from non-experts at far lower expense.
The study set out to test non-expert performance on five established tasks: affect recognition in headlines, word similarity judgments, recognizing textual entailment, temporal ordering of events, and word sense disambiguation. Researchers collected ten independent labels per item via Mechanical Turk and compared the results directly to existing expert gold standards using agreement metrics such as Pearson correlation and majority-vote accuracy.
For every task, non-expert labels reached high agreement with experts once multiple annotations were averaged. Four non-expert labels per item typically matched the reliability of one expert; ten labels produced even stronger results. A bias-correction model that accounts for individual worker accuracy improved performance by roughly four percentage points on two categorical tasks. Classifiers trained on non-expert affect labels performed as well as or better than those trained on single-expert labels.
These outcomes show that crowdsourced annotations can replace or supplement expert work for many labeling projects, cutting costs to hundreds of labels per dollar while maintaining usable quality. The approach also surfaced and corrected an error in one expert gold set.
The findings support wider adoption of Mechanical Turk for dataset creation, provided projects collect redundant labels and apply simple quality controls. Additional testing on new tasks, larger scales, and more complex annotation schemes would strengthen before full-scale deployment.
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