  While it has long been recognized that a team of individual learning agents
can be greater than the sum of its parts, recent work has shown that larger
teams are not necessarily more effective than smaller ones. In this paper, we
study why and under which conditions certain team structures promote effective
learning for a population of individual learning agents. We show that,
depending on the environment, some team structures help agents learn to
specialize into specific roles, resulting in more favorable global results.
However, large teams create credit assignment challenges that reduce
coordination, leading to large teams performing poorly compared to smaller
ones. We support our conclusions with both theoretical analysis and empirical
results.
