The landmark 21st is now seen as little more than an excuse to have a great party – before keeping the fun going for at least the next nine years.

The study, conducted by researchers at Melbourne’s Brotherhood of St Laurence charity, carried out from the time babies were born in two Melbourne suburbs in 1990, found that only 38 per cent of them believed they had reached maturity by the age of 21.

Another 13 per cent were adamant that they were not adults when their 21st birthday came around. The remaining 49 per cent couldn’t decide.