This paper presents evidence for two claims: (a) that the underlying contrast
between stops in Swiss German dialects is based purely on quantity and (b) that
the duration of the stop closure is its sole reliable phonetic reflex, i.e. there is a
geminate–singleton opposition acoustically manifested in long–short closure
duration. Using production and perception data on initial, medial and final stops
in Thurgovian, a dialect spoken in north-eastern Switzerland, we show that the
pattern of phrase-medial contrast neutralisation supports both arguments: when
the extra phonological length position of a geminate is not syllabifiable, the closure
duration shortens and underlying geminates and singletons become indistinguishable.
The perception data in particular make evident that closure duration
is the crucial cue of the underlying contrast, because, in the absence of this
phonetic correlate, listeners can no longer discriminate an underlying geminate
from a singleton. The results bear not only on central issues concerning the
representation of geminates but also on some intricacies of the phonology–phonetics interface.