On the rarity of pre-aspirated stops1

Pre-aspirated stops, known to be quite rare in the world’s languages, are shown herein to be significantly rarer still. Their aspiration component is typically reinforced by an oral gesture that is influenced by the following stop and/or the preceding vowel. Alternatively, the aspiration component weakens to zero and is replaced by vowel length. In this typological study I document the phonetic details of so-called pre-aspirates and offer phonetic explanations for their rarity and their diachronic instability