Australian Questioning Intonation, or
High Rising Tone, or
Upspeak, is a dialect variant where sentences end on an upward
inflection.
Although it is primarily used by young, female working-class Australians, its effects are now being heard much further afield in the English speaking world, in the U.K. and North America, for example.
Its origins are unclear. Audio recordings of Australian speakers dating to the 1960's show it to be absent, and its use appears to have begun between then and the 1980's.
One researcher theorises that its use came about as a reaction of native Australians to the large post-war influx of immigrants, as a method of eliciting a response to the question of whether or not they were being clearly understood.