Citations are classified by a deep learning model that is trained to identify three categories of citation statements: those that provide contrasting or supporting evidence for the cited work, and others, which mention the cited study without providing evidence for its validity.Citations are classified by rhetorical function, not positive or negative sentiment.
Citations are not classified as supporting or contrasting by positive or negative keywords.
A Supporting citation can have a negative sentiment and a Contrasting citation can have a positive sentiment. Sentiment and rhetorical function are not correlated.
Supporting and Contrasting citations do not necessarily indicate that the exact set of experiments were performed. For example, if a paper finds that drug X causes phenomenon Y in mice and a subsequent paper finds that drug X causes phenomenon Y in yeast but both come to this conclusion with different experiments—this would be classified as a supporting citation, even though identical experiments were not performed.
Citations that simply use the same method, reagent, or software are not classified as supporting. To identify methods citations, you can filter by the section.
For full technical details including exactly how we do classification, what classifications and classification confidence means please read our recent publication describing how scite was built: https://doi.org/10.1162/qss_a_00146
A few examples:
Supporting citation statement
Here, the statement In agreement with previous work .... indicates support, while ... the trisomic clones showed similar aberrations, albeit to a lesser degree (Suppplemental Figure S2B) ... provides evidence for this supporting statement. Hence, this citation is classified as supporting because the authors of the citing study provide primary evidence supporting (Nicholson et al 2015), they do not merely mention evidence provided by others.
Contrasting citation statement
Here, the statement These findings do not replicate previous studies... indicates a contrast between findings, while showing either increased (e.g., Phan et al. 2006) ...magnitude of dorsal anterior specifies the evidence that the citing study contrasts. Hence, this citation statement is classified as contrasting because the authors provide contrasting evidence, not repeat someone else's conclusion.
Mentioning citation statements
This citation statement refers to Phan et al. 2006 without providing evidence that supports or contrasts the claims made the cited study.
Here, the statement Consistent with these findings.... sounds supportive, but, in fact, cites two previous studies: [87] and [27] without providing evidence for either. Such cites can be valuable, as they establish connections between observations made by others, but they do not provide primary evidence to support or contrast the cited studies. Hence, this citation is classified as mentioning.
The following two citation statements agree with conclusions made previously by others, but do not provide primary evidence to either support or contrast them. Thus, these statements are classified as mentioning. 
If you do find citation statements that are not classified correctly, please flag them and suggest your classification. Your suggestion will be reviewed independently by two experts and, if both agree, will be accepted and labeled as "Expert classified."