The Great Vowel Shift was a series of changes in the pronunciation of the English language that took place primarily between 1350 and the 1600s and 1700s, beginning in southern England and today having influenced effectively all dialects of English. Through this vowel shift, all Middle English long vowels changed their pronunciation. Some consonant sounds changed as well, particularly those that became silent; the term Great Vowel Shift is sometimes used to include these consonant changes. The Great Vowel Shift was a series of changes in the pronunciation of the English language that took place primarily between 1350 and the 1600s and 1700s, beginning in southern England and today having influenced effectively all dialects of English. Through this vowel shift, all Middle English long vowels changed their pronunciation. Some consonant sounds changed as well, particularly those that became silent; the term Great Vowel Shift is sometimes used to include these consonant changes. English spelling began to become standardized in the 15th and 16th centuries, and the Great Vowel Shift is the major reason English spellings now often considerably deviate from their representation of English pronunciations. The Great Vowel Shift was first studied by Otto Jespersen (1860–1943), a Danish linguist and Anglicist, who coined the term. The causes of the Great Vowel Shift have been a source of intense scholarly debate, and, as yet, there is no firm consensus. The greatest changes occurred during the 15th and 16th centuries. Some scholars have argued that the rapid migration of peoples from northern England to the southeast following the Black Death caused a mixing of accents that forced a change in the standard London vernacular. Others argue that the influx of French loanwords was a major factor in the shift. Yet others assert that because of the increasing prestige of French pronunciations among the middle classes (perhaps related to the English aristocracy's switching from French to English around this time), a process of hypercorrection may have started a shift that unintentionally resulted in vowel pronunciations that were less like French instead of more. An opposing theory states that the wars with France and general anti-French sentiments caused hypercorrection deliberately to make English sound less like French. The main difference between the pronunciation of Middle English in the year 1400 and Modern English (Received Pronunciation) is in the value of the long vowels. Long vowels in Middle English had 'continental' values, much like those in Italian and Standard German; in standard Modern English, they have entirely different pronunciations. The differing pronunciations of English vowel letters do not stem from the Great Shift as such but from the fact that English spelling failed to be adapted to the changes. German had undergone vowel changes quite similar to the Great Shift in a slightly earlier period but the spelling was changed accordingly (e.g. Middle High German bīzen → modern German beißen 'to bite'). This timeline shows the main vowel changes that occurred between late Middle English in the year 1400 and Received Pronunciation in the mid-20th century by using representative words. The Great Vowel Shift occurred in the lower half of the table, between 1400 and 1600–1700. The changes that happened after 1700 are not considered part of the Great Vowel Shift. Pronunciation is given in the International Phonetic Alphabet: Before the Great Vowel Shift, Middle English in Southern England had seven long vowels, /iː eː ɛː aː ɔː oː uː/. The vowels occurred in the words bite, meet, meat, mate, boat, boot, out and many more. The words had very different pronunciations in Middle English from their pronunciations in Modern English. Long i in bite was pronounced as /iː/ so Middle English bite sounded like Modern English beet /biːt/; long e in meet was pronounced as /eː/ so Middle English meet sounded similar to Modern English mate /meɪt/; long a in mate was pronounced as /aː/, with a vowel like Scottish English ah in father or General American short o in cot /kɑːt/; and long o in boot was pronounced as /oː/, similar to modern oa in General American boat /oʊ/. In addition, Middle English had a long /ɛː/ in beat, like modern short e in bed but pronounced longer, and a long /ɔː/ in boat. After around 1300, the long vowels of Middle English began changing in pronunciation. The two close vowels, /iː uː/, became diphthongs (vowel breaking), and the other five, /eː ɛː aː ɔː oː/, underwent an increase in tongue height (raising).