Dealing with phonological variations is important for speech processing. This article
addresses whether phonological variations introduced by assimilatory processes are
compensated for at the pre-lexical or lexical level, and whether the nature of variation
and the phonological context influence this process. To this end, Swedish nasal regressive
place assimilation was investigated using the mismatch negativity (MMN) component.
In nasal regressive assimilation, the coronal nasal assimilates to the place of articulation
of a following segment, most clearly with a velar or labial place of articulation,
as inutan mej“without me” > [ʉːtam mɛjː]. In a passive
auditory oddball paradigm, 15 Swedish speakers were presented with Swedish phrases
with attested and unattested phonological variations and contexts for nasal assimilation.
Attested variations – a coronal-to-labial change as inutan“without”
> [ʉːtam] – were contrasted with unattested variations – a labial-to-coronal change
as inutom“except” >∗[ʉːtɔn] – in appropriate
and inappropriate contexts created bymej“me” [mɛjː] anddej“you”
[dɛjː]. Given that the MMN amplitude depends on the degree of variation between two
stimuli, the MMN responses were expected to indicate to what extent the distance between
variants was tolerated by the perceptual system. Since the MMN response reflects not
only low-level acoustic processing but also higher-level linguistic processes, the
results were predicted to indicate whether listeners process assimilation at the pre-lexical
and lexical levels. The results indicated no significant interactions across variations,
suggesting that variations in phonological forms do not incur any cost in lexical
retrieval; hence such variation is compensated for at the lexical level. However,
since the MMN response reached significance only for a labial-to-coronal change in
a labial context and for a coronal-to-labial change in a coronal context, the compensation
might have been influenced by the nature of variation and the phonological context.
It is therefore concluded that while assimilation is compensated for at the lexical
level, there is also some influence from pre-lexical processing. The present results
reveal not only signal-based perception of phonological units, but also higher-level
lexical processing, and are thus able to reconcile the bottom-up and top-down models
of speech processing.
