The lengthened vowels did not merge with any of the older long vowels, as can be judged from evidence in texts from certain areas and the modern dialects that retain such a distinction. Instead, the lengthening produced four new long vowels (see Middle Dutch phonology). They are conventionally denoted with a macron, and the original long vowels are denoted with a circumflex. The exact phonetic nature of the two types of long vowel is unknown and probably differed by area. Differences in vowel height, backness and/or diphthongal quality may have played a role. The following table shows the changes: