UC Santa Cruz

Phonetic dispersion has been proposed as an explanation for a number of sound-change phenomena, including vowel chain shifts, compensatory sound change, and universal trends within phoneme inventories. These explanations usually take the form of speaker-based accounts (principally H&H theory; see Lindblom, 1986). But there is a lack of empirical evidence for speaker-based approaches (McGuire and Padgett, 2011), which have also been criticized as being teleological (e.g. Blevins, 2004). This thesis explores an alternative, listener-based, perceptual account of dispersion: the Filtering Listener (Labov, 1994: 587; Wedel, 2006; McGuire and Padgett, 2011). Based in exemplar theory (Nosofsky, 1986; Pierrehumbert, 2001; etc.), the Filtering Listener hypothesis argues that when listeners are confronted with phonetically ambiguous percepts, they may not store them to phonetic memory. In turn, these unstored percepts do not update the phonemic categories of the listener, and are thus not reflected in that listener's future productions. This thesis explores the Filtering Listener as a mechanism for contrast maintenance and source of sound change, and tests its predictions experimentally in a perceptual recognition task. Participants heard phonetically ambiguous target words and phonetically unambiguous control words in noise and were asked to identify them, following Goldinger (1996). This task was repeated in 4 identical experimental blocks. Results showed that participants improved their accuracy of recognition much more over the course of the experiment for the unambiguous condition, suggesting that their storage of ambiguous percepts was degraded in memory. This provides promising preliminary evidence for the Filtering Listener; further replication, with more tightly controlled pilot studies, is required.