[PS-1.1] Adult learning and language simplification

Atkinson, M. 2, 1 , Smith, K. 1 & Kirby, S. 1

1 University of Edinburgh
2 University of Stirling

Languages spoken in larger populations are relatively simple. One explanation for this is that larger groups have greater proportions of adult learners, and that these learners introduce simplifications at the level of the individual which can reduce linguistic complexity at the level of the group. We assess this in three experiments. In Experiment 1, we show that individual adult learners trained on a morphologically-complex miniature language simplify its morphology. In Experiment 2, we explore how these simplifications may propagate through subsequent learning. We use the languages produced by the participants of Experiment 1 as input for a second set of learners, manipulating (i) the proportion of their input which is simplified, and (ii) the number of speakers they receive their input from. We find, contrary to expectations, that mixing the input from multiple speakers nullifies the simplifications. In Experiment 3, we consider language use as a mechanism for simplification. In interaction between individuals differing in linguistic competence, the speaker of a more complex variant simplifies their language during interaction. We suggest that adult learning is a plausible explanation for languages spoken by more people having simpler morphology, but that accommodation to non-native speakers may be a key linking mechanism.