Speaker: Juliet Stanton (MIT)
Title: Environmental shielding is contrast preservation
Date: Monday, March 30th
Time: 5-6:30
Place: 32D-831
The term environmental shielding refers to a class of processes where the phonetic realization of a nasal stop depends on its vocalic context. In Kaiwá (Tupí; Bridgeman 1961), for example, plain nasal stops are realized as prenasalized stops before oral vowels (i.e. /ma/ > [mba]) but as nasal stops before nasal vowels (i.e. /mã/ > [mã]). Herbert (1986:199) claims that the purpose of shielding is to protect a contrast between oral and nasal vowels. If Kaiwá /ma/ were realized as [ma], without the intervening [b], [a] would likely carry some degree of perseveratory nasal coarticulation and be less distinct from its nasal counterpart /ã/ as a result.
This paper provides several arguments that Herberts position is correct that environmental shielding is contrast preservation, and that any successful analysis of shielding must make explicit reference to contrast. Results from a survey of over 150 languages reveal a stark asymmetry in the typology of shielding: all languages that exhibit shielding also license a contrast in vocalic nasality (see also Herbert 1986:219). In addition, further asymmetries within the typology mirror known cross-linguistic asymmetries in the direction and extent of nasal coarticulation. I propose an analysis referencing auditory factors that predicts these asymmetries, and show that its broader predictions, though not yet fully investigated, appear to be on the right track.