Canadian raising
Canadian raising is a phonetic phenomenon that occurs in varieties of the English language, especially Canadian English, in which diphthongs are "raised" before voiceless consonants (e.g., /p/, /t/, /k/, /s/, /f/). For example, IPA /aɪ/ (SAMPA /aI/, the vowel of "eye") and /aʊ/ (/aU/, the vowel of "loud") become /ʌɪ/ (/VI/) and /ʌʊ/ (/VU/), respectively, the /a/ (as in "father") component of the diphthong going from a low vowel to the mid vowel /ʌ/ (/V/)/ (as in "up"). As /ʌʊ/ (/VU/) sounds similar to /oʊ/ (/oU/) (as in "road), the Canadian pronunciation of "about the house" may sound like *"a boat the hoas" to non-Canadians. Some stand-up and situation comedians exaggerate this to *"aboot the hoos" for comic effect.
Despite its name, the phenomenon is not restricted to Canada. The example above deals with the /aʊ/ (/aU/ diphthong, but, as noted, the /aɪ/ (/aI/) diphthong can be affected as well. So, whereas the General American pronunciations of "rider" and "writer" are identical /ɹaɪɾɚ/ (/raI4@r/), those whose dialects include Canadian raising will pronounce them as /ɹaɪɾɚ/ (/raI4@r/) and /ɹʌɪɾɚ/ (/rVI4@r/), respectively. It is this raising of /aɪ/ (/aI/) which can be found in the United States, especially in the Pacific Northwest. Note also that Canadian raising preserves the etymological /t/ in "writer," even though in Canadian English, as in most other versions of North American English, the /t/ and /d/ are merged to /ɾ/ (/4/) before unstressed vowels.
The phenomenon of Canadian raising may be related historically to a similar phenomenon that exists in Scots and Scottish English. The Scots Vowel Length Rule lengthens a wide variety of vowel sounds in several environments, and shortens them in others; "long" environments include when the vowel precedes a number of voiced consonant sounds. This rule also conditions /aɪ/ — /aI/ in the long environments and /ʌɪ/ — /VI/ in the short environments.
