A unifying explanation of the Great Vowel Shift, Canadian Raising and Southern Monophthonging

It is argued that three historical sound changes in English resulted from the enhancement of a duration cue involved in the signaling of phonological contrasts. In the case of the Great Vowel Shift (ca. 1600) the contrast involved was the opposition between long and short vowels, while in the case of Canadian Raising and Southern Monophthonging (ca. 1900) it is the laryngeal opposition in coda obstruents, whose most salient cue is a duration difference in sonorant rime portions preceding the coda obstruent. One of the two phonetic policies enhancing the duration distinctions is the raising of long vowels, which enhances their perceived longer duration by virtue of the illusion of a shorter time needed for the production of vowel targets, as occurred in the Great Vowel Shift. The second mechanism is the strengthening the second elements of closing diphthongs, which enhances their perceived shorter duration by virtue of an illusory conversion of the second elements into [w j], as happened in the case of Canadian Raising, and its counter-policy, the lengthening of the first element at the expense of the second, as happened in the case of Southern Monophthonging.