Source
Limor Raviv, Antje Meyer and Shiri Lev-Ari (2019), Proc. R. Soc. B 286:20191262, LIT-825; read in NOTE-628 (main text; the supplementary models were not read). What the experiment showed is THEORY-164, which this entry extends.
The claim
When people who share no language build one by communicating, the size of the group they communicate in shapes the result. With everyone able to talk to everyone and the same total amount of interaction, members of larger groups end with languages whose forms map more systematically onto meanings, reach that structure sooner, and differ less from one group to the next. Members of small groups can sustain idiosyncratic, holistic labels, because with few partners and much shared history they can memorise them. The cause the paper argues for is input variability: more partners means more competing variants to cope with, which favours forms that are predictable from their meaning. The authors argue that the result should scale to real communities and supports community size as a driver of language evolution.
The experiment had two sizes, four and eight, with 12 groups each, of Dutch adults, over a written channel, in a meaning space designed to reward compositional structure. Input variability was measured, not varied, and less shared history per pair travels with group size.
What would settle it
The promote_when: a replication by other hands or with another meaning space and channel, and a study that manipulates input variability at a fixed group size. Correlations across natural languages cannot settle it, since they carry the confounds of network density and adult second-language learners that the experiment removed.