The relationship between quality and quantity in research (Vol. 41, No. 5)

A new sociophysics model has led to quantification of the hitherto intuitive notion of critical mass in research. By treating research groups as complex systems, in which interactions between individuals are taken into account, a relationship between quality and quantity has been established. The model posits that the collaborative effect dominates quality, being an order of magnitude stronger than other factors such as individual calibre or institutional prestige. This means the strength of a research community is greater than the sum of its parts.

The research shows that there exist two critical masses, the sizes of which are discipline dependent. A small group is vulnerable and must strive to achieve the lower critical mass. Up to approximately twice this value, research quality is strongly dependent on the quantity of researchers. However, once beyond the value of the upper critical mass, research quality does not significantly improve with team quantity (the figure illustrates this for physics). The upper critical mass is interpreted as the maximum number of colleagues with whom an individual researcher can meaningfully communicate. When a group grows larger than this value, it tends to fragment. The lower critical mass is half the upper value, and for biology, physics and Earth sciences is 10, 13, and 15, while for pure and applied mathematics is about 2 and 6 respectively.

The research draws on data from evaluation exercises in Britain and France and suggests that to maximise the overall strength of a discipline, it is best to provide support for medium-size research teams to help them reach the upper critical mass, but that a policy of continued concentration is less effective above this limit.