[Letter to the Editor] Does conceptual compositionality affect language complexity? Comment on Lou-Magnuson and Onnis

In a recent article, Lou-Magnuson and Onnis (2018) focus attention on the fact that `languages with smaller and more isolated speaker populations tend to make much greater use of morphology' (p. \X2791\X). That languages pattern in this way is intriguing. For purposes of communication, syntax and morphology are equally effective; so it is not obvious why smaller speaker populations should exhibit this tendency. The authors claim to offer the `first causal explanation' (p. \X2792\X) for the effect, which is termed `morphology bias' below. Their explanation takes the form of an agent-based simulation in which a process considered important for grammaticalization---reanalysis---is seen to increase an integer reflecting emergence of morphological structure. Testing of this model is said to reveal that `[s]mall populations with dense connections are able to support sustained reanalysis'. The conclusion then drawn is that that this causes `... the average level of morphological composition to be higher' (p. \X2814\X).