Wilf Douglas's dictionary compiled from research done between the late 1930's and 1970 is held in high esteem by many Noongar people. His description of Noongar dialects contrasts significantly with Tindale's map which is often taken to indicate dialect but should be seen more of an indicator of territorial boundaries than dialect boundaries. Douglas recorded 6 different pronunciations of the word 'Noongar'. He also observed that dental consonants (-ny, -ly -tj) in the south are replaced by alveo-dentals in the north (-n,l,-t).(see pronunciation guide)
The other major dialect shift that Wilf Douglas observed is the loss of the last vowel that occurs in the souther dialects. 'yok' versus 'yoka' for woman for instance. This loss of the last vowel is quite pervasive and is often accompanied by a subtle diphthong created by the substitution of a retroflexed consonant for alveolar as in quenda vs quernt for bandicoot. This dialect shift is alive and well amongst Great Southern people today despite the intermingling of people and the language as a whole
Carl von Brandenstein studied Noongar from 1964 to 1984 mostly from informants like Charlie Dabb at Esperance. He regarded this dialect shift as an artificial creation as a result of conflict that occurred within the previous 200 -300 years between the Western Desert 'law' makers and the more traditional people of the South West.
"My main reason... is to furnish proof of my contention that Nyungar is an artifical language, produced by a number of clever men, if not by a single individual, as the result of a socio-political crisis, whcih took place some time before the arrival of the white man in Western Australia" Nyungar Anew(1988), C von Brandenstein. p.v.
Although his contention is beguiling it is perhaps reading too much into the evidence. It is equally possible to hypothesize that the southern(Mirnang) form is the oldest and that the adoption of western desert word construction(with nouns ending with vowels)could have occurred as a result of interaction along the west coast trade routes which extended to the north east and north from Perth. The conflict that he describes at Esperance could be seen to be a local affair.