February 14, 2013

Guest Speaker: Peter Graff (Feb. 15, 2013)

 Speaker: Peter Graff (MIT) http://web.mit.edu/graff/www/

Title: "Communicative Efficiency in Phonology"

Time: Friday Feb. 15th, 3pm.

Place: Sid Smith 560A (ground floor) (Sid Smith is located at 100 St. George St.)

In this talk, I present novel typological and behavioral evidence suggesting that phonological patterns derive from communicative efficiency: The cross-linguistic patterning of sounds and words as well as the ways in which speakers produce them are geared towards achieving a high rate of information transmission given the effort invested by the speaker (Lindblom, 1990; Flemming 1995). First, I show for the first time that the relative occurrence frequencies of different sounds in 60 languages from 25 major language families may be understood in terms of communicative efficiency. Building on well-known findings about the relative perceptibility of voicing contrasts in different contexts (Raphael, 1981), differences in the effort involved in articulating different voiced stops (Ohala & Riordan, 1979), and information theory in the sense of Shannon (1948), I derive a measure of communicative efficiency for frequency distributions over voiced and voiceless stops in context. I show that the efficiency of natural language frequency distributions over those categories is significantly greater than expected from chance.

Next, I present evidence that redundancy in the lexicon is not randomly distributed, but instead exists to supplement distinctions between meaningful linguistic units that are hard to perceive. Specifically, I show that the number of words disambiguated solely by a given contrast (i.e., minimal pairs) decreases as a function of the perceptibility of that contrast, beyond what is expected from the probabilistic patterning of the contrasting sounds. The lexicon as a whole is thus organized in ways that minimize the confusability of words given the effort invested in their production.

Finally, I present behavioral evidence suggesting that language production at the sound level seeks to maximize the rate of information transmission and minimize speaker effort (cf Aylett & Turk, 2004). I report on a phonetic corpus study of F2-transitions into stops and stop burst durations showing that these acoustic cues to place of articulation stand in a probabilistic trade-off relation. When stop bursts are long, F2-transitions are correspondingly small, while when stop bursts are short, F2-transitions are correspondingly large. This trade-off is expected if the articulatory effort invested in the production of the burst is reduced where formant transitions convey sufficient information for the listener to recover the place of a stop.

Taken together, these results suggest that communicative efficiency shapes human language phonology, the lexicon, and the ways in which humans use sounds and words to communicate intended meanings.

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