One of the most widely studied observations in linguistic phonetics is that, all else being equal, vowels are longer before voiced than before voiceless obstruents. The causes of this phonetic generalization are, however, poorly understood and several competing explanations have been proposed. No studies have so far measured vowel duration before stops with yet another laryngeal feature: ejectives. This study fills this gap and presents results from an experiment that measures vowel duration before stops with all three laryngeal features in Georgian and models effects of both closure and voice onset time (VOT) on preceding vowel duration at the same time. The results show that vowels have significantly different durations before all three series of stops, voiced, ejective, and voiceless aspirated, even when closure and VOT durations are controlled for.
The results bear several implications for the discussion of causes of vowel duration differences: the data support the hypotheses that claim that laryngeal gestures, temporal compensation, and closure velocity affect vowel duration. Some explanations, especially perceptual and airflow expenditure explanations, are considerably weakened by the results.