  With teams growing in all areas of scientific and scholarly research, we
explore the relationship between team structure and the character of knowledge
they produce. Drawing on 89,575 self-reports of team member research activity
underlying scientific publications, we show how individual activities cohere
into broad roles of (1) leadership through the direction and presentation of
research and (2) support through data collection, analysis and discussion. The
hidden hierarchy of a scientific team is characterized by its lead (or L)-ratio
of members playing leadership roles to total team size. The L-ratio is
validated through correlation with imputed contributions to the specific paper
and to science as a whole, which we use to effectively extrapolate the L-ratio
for 16,397,750 papers where roles are not explicit. We find that relative to
flat, egalitarian teams, tall, hierarchical teams produce less novelty and more
often develop existing ideas; increase productivity for those on top and
decrease it for those beneath; increase short-term citations but decrease
long-term influence. These effects hold within-person -- the same person on the
same-sized team produces science much more likely to disruptively innovate if
they work on a flat, high L-ratio team. These results suggest the critical role
flat teams play for sustainable scientific advance and the training and
advancement of scientists.
