Simplifications made early in learning can reshape language complexity: an experimental test of the Linguistic Niche Hypothesis

Languages spoken in larger populations seem to be relatively simple. One possible explanation is that this is a consequence of the simplifying influence of non-native speakers: adult learners tend to reduce complexity during learning, and large languages tend to have a higher proportion of non-native speakers. This Linguistic Niche Hypothesis, that languages adapt to their social niche, receives some statistical support from typological studies which show negative correlations between population size or number of non-native speakers and morphological complexity. Here I report an experimental test of this hypothesis, using two artificial language learning experiments to explore the impact of simplifications made by non-native-like early learners on morphological complexity. These experiments show that the presence of non-native-like early learners in a population can lead to the simplification of that language's morphology as a result of inter-generational language transmission, providing experimental support for the Linguistic Niche Hypothesis.