The actuation of sound change

In William Shakespeare's times, 'knee' and 'knot' were pronounced with a /k/, just like German does today. But why did English and not German drop the /k/?

This question is part of the actuation of sound change, recognised as one of the greatest challenges in linguistics, and which is about explaining why sound change happens, and why languages can follow such different paths of sound change.

The actuation puzzle remains unsolved principally because the beginning of sound change is so gradual that it is undetectable even with modern instrumentation. Yet a breakthrough is essential for explaining why languages split and diversify.

The project remedies this deficiency by determining how the cognitive mechanisms that control human speech processing, the social factors that bind individuals together, and the phonetic properties that shape a community's dialect, can, in combination, cause the sounds of the worlds languages to become unstable and change.

The methodological innovation is to recast the elusive actuation puzzle as an empirically tractable transformation of an input (A) into an output (B).

Here A and B are two closely related, geographically proximal, living dialects whose sound patterns differ in whether one or more common sound changes have taken place.

The actuation puzzle is then solved with experiments in human speech imitation and computational modelling in order to estimate which combination of cognitive, social, and phonetic factors transforms A into B.

Generalisation is achieved by selecting dialect pairs from Bantu, Indo-European, and Japanese languages that differ markedly in their sound patterns and sociocultural background.

The wider scientific impact lies in the commonality with many disciplines including ecology, economics, and geoscience in understanding complex systems (here: language) in which interactions between sub-components (here: communicating speakers) cause transitions (here: sound change) that are unevenly distributed in time.