Coarticulation

Phonology

Coarticulation is the overlapping of articulatory movements for adjacent speech sounds. When we speak, the tongue, lips, jaw, and velum do not move in discrete steps from one sound to the next; instead, movements for upcoming sounds begin before the current sound is complete, and traces of preceding sounds persist into the next. At any point in the speech signal, acoustic information about two or more phonemes is present simultaneously.

Types

Anticipatory (Forward) Coarticulation

The articulation of a current sound is influenced by a following sound. The articulators begin moving toward the next target before finishing the current one.

In screws /skruːz/, lip rounding for /uː/ and /r/ extends backward over the entire word — even the initial /s/ may be produced with rounded lips
In keen /kiːn/, the /k/ is produced further forward in the mouth (palatalised) in anticipation of the front vowel /iː/

Anticipatory coarticulation is thought to reflect high-level articulatory planning.

Perseverative (Backward/Carryover) Coarticulation

The articulation of a current sound is influenced by a preceding sound, due to articulatory inertia.

After a nasal consonant, the following vowel may carry nasal quality (see Nasalisation)
After a rounded vowel, a following consonant may retain some lip rounding

Relationship to Connected Speech

Coarticulation is the physical mechanism underlying many Connected Speech processes:

Assimilation — Coarticulatory overlap causes one sound to take on features of its neighbour (ten bags → /tem bæɡz/)
Elision — When coarticulation is extreme, a sound may be effectively eliminated
Linking — Smooth transitions between words result from continuous articulatory movement

In isolated, carefully articulated words, coarticulation is reduced. In fluent speech, it is pervasive — which is why Connected Speech sounds so different from citation forms.

Communicative Function

Coarticulation is not merely articulatory laziness. It serves communication by spreading phonetic information across time, making the speech signal more redundant and therefore more robust to noise. Listeners use coarticulatory cues to anticipate upcoming sounds, facilitating faster processing.

Teaching Relevance

Understanding coarticulation helps explain to learners why fluent English sounds different from the word-by-word pronunciation they encounter in dictionaries. It provides the rationale for teaching Connected Speech Processes explicitly: these are not "sloppy" speech but natural consequences of how the human articulatory system operates.