SCOTS living in towns and villages have baffled linguistic experts for years by speaking to their family and friends in one accent, while using another "posh" voice in the workplace.

The most likely reason for the phenomenon is that many people want to be better understood by outsiders.

Now an academic is to lead a team from Glasgow University who will attempt to fully understand the issue, which is known as "bidialectalism".

Dr Jennifer Smith, a senior lecturer in English Language, hopes to uncover why increasing numbers of people have developed a dual linguistic identity and are now using two separate dialects in their everyday lives.

Ms Smith herself returned to her home town of Buckie in Moray after years abroad and was accused of talking differently or "posh".

Bidialectalism is thought to lead to a dual identity particularly amongst younger Scots, who still regard speaking differently in their own community as socially unacceptable.

The study will investigate the growth of bidialectalism and look at what it will mean to the long- term future of linguistics in Scotland.

It will focus on Buckie, the fishing town on the Moray Firth that was the largest town in the old Banffshire, and will be led by "native speaker" Ms Smith.

The academic has also observed how some of her older family members had great difficulty in speaking in anything other than the local dialect.

She said previous studies have shown that people in smaller communities develop a local dialect, which is used among members of the same community, but also a more formal standard dialect, which is used when talking to members outside the local community.

It is thought that this increasing bidialectalism may be the root of a new dual identity within younger generations, whereby one dialect is assumed in the local community and a different one used elsewhere.

The team will measure the speech patterns of three generations of speakers ranging from 15 to 80 years of age.

The subjects will be interviewed twice, firstly by a native speaker of the dialect – also known as an insider – and then again by someone who has no ties to the area, or an outsider.

The team want to know whether there are changes in patterns of bidialectalism over the three generations. They will use a range of quantitative analysis techniques to test for variations in speech patterns between the age groups, looking for where and when speakers switch dialects, whether all speakers do this fluently, in which situations people switch dialects and how their speech patterns change.

Ms Smith, speaking of her own personal experiences, said: "The local Buckie dialect is used the majority of the time when talking to other community members, and indeed speaking 'posh' is a big no-no within the community.

"However, speakers do use a more standard variety – English with a Scottish accent – in certain situations, such as in school and talking to outsiders."

Ms Smith said this ability to switch between local and standard dialects is particularly noticeable amongst the younger generations, "but the question is where, when and how do speakers switch? Can all speakers switch fluently or does it depend on the individual person?"

She asked: "Do certain situations make people switch more than others? Do speakers switch words, sounds and grammar or only certain parts of the language?

"We're hoping that this study will help us learn how our language is evolving, and what to expect going into the future."

She said that when exiles reverted to their native speech they often sounded more dialectical than the people who had stayed put.

Ms Smith added: "It's due to the fact that a dialect in a community is constantly changing, but if you've been away, your dialect is stuck in the time before you left. This is known as 'colonial lag'."