Assimilation

Assimilation

If speech is thought of as a string of sounds linked together, assimilation is what happens to a sound when it is influenced by one of its neighbours. For example, the word ‘this’ has the sound s at the end if it is pronounced on its own, but when followed by ʃ in a word such as ‘shop’ it often changes in rapid speech (through assimilation) to ʃ, giving the pronunciation ðiʃʃɒp. Assimilation is said to be progressive when a sound influences a following sound, or regressive when a sound influences one which precedes it; the most familiar case of regressive assimilation in English is that of alveolar consonants, such as t, d, s, z, n, which are followed by non-alveolar consonants: assimilation results in a change of place of articulation from alveolar to a different place. The example of ‘this shop’ is of this type; others are ‘football’ (where ‘foot’ fυt and ‘ball’ bɔ l combine to produce fυpbɔ l) and ‘fruit-cake’(fru t + keik → frυ kkeik). Progressive assimilation is exemplified by the behaviour of the ‘s’ plural ending in English, which is pronounced with a voiced z after a voiced consonant (e.g. ‘dogs’ dɒ z) but with a voiceless s after a voiceless consonant (e.g. ‘cats’ k ts).

The notion of assimilation is full of problems: it is often unhelpful to think of it in terms of one sound being the cause of the assimilation and the other the victim of it, when in many cases sounds appear to influence each other mutually; it is often not clear whether the result of assimilation is supposed to be a different allophone or a different phoneme; and we find many cases where instances of assimilation seem to spread over many sounds instead of being restricted to two adjacent sounds as the conventional examples suggest. Research on such phenomena in experimental phonetics does not usually use the notion of assimilation, preferring the more neutral concept of coarticulation.