  Co-authored articles tend to be more cited in many academic fields, but is
this because they tend to be higher quality or is it an audience effect:
increased awareness through multiple author networks? We address this unknown
with the largest investigation yet into whether author numbers associate with
research quality, using expert peer quality judgements for 122,331 non-review
journal articles submitted by UK academics for the 2014-20 national assessment
process. Spearman correlations between the number of authors and the quality
scores show moderately strong positive associations (0.2-0.4) in the health,
life, and physical sciences, but weak or no positive associations in
engineering, and social sciences. In contrast, we found little or no
association in the arts and humanities, and a possible negative association for
decision sciences. This gives reasonably conclusive evidence that greater
numbers of authors associates with higher quality journal articles in the
majority of academia outside the arts and humanities, at least for the UK.
Positive associations between team size and citation counts in areas with
little association between team size and quality also show that audience
effects or other non-quality factors account for the higher citation rates of
co-authored articles in some fields.
