What is a ‘chain shift’?
Chain shifts are a series of interrelated vowel movements (regarding the pronunciation).
‘Interrelated’ means that a vowel moves because another vowel moves (-> causal relationship). This usually happens to vowels that are adjacent to each other in the vowel system.
There are two types of chain shift:
1. Push chains:
In push chains, vowel A moves into the direction of vowel B. As a consequence, vowel B moves out of the way.
The (not universally accepted) explanation for this is that linguistic systems try to avoid homophony (= two sounds being identical), i.e. maintenance of contrast.
2. Pull chains:
In pull chains, vowel A moves away from its previous position. As a consequence, an adjacent vowel B moves into the position that was previously occupied by A.
The explanation for this is that vowel systems tend to maintain equal spacing between vowels, i.e. optimisation of available space
