Figure 16. Right: benefit of using full-text articles.

Document frequencies (number of documents in which a word appears) for terms from the NeuroSynth vocabulary, in the NeuroSynth corpus ($x$ axis) and the NeuroQuery corpus ($y$ axis). Words appear in much fewer documents in the NeuroSynth corpus because it only contains abstracts. Even when considering only terms present in the NeuroSynth vocabulary, the NeuroQuery corpus contains over 3M term-study associations – 4.6 times more than NeuroSynth. Left: Most terms occur in few documents Plot of the document frequencies in the NeuroQuery corpus, for terms in the vocabulary, sorted in decreasing order. While some terms are very frequent, occurring in over 12 000 articles, most are very rare: half occur in less than 76 (out of 14 000) articles.