The way a person speaks is an intrinsic part of their identity. It's tribal, marking a speaker as being from one social group or another. Accents are a sign of belonging as much as something that separates communities.

Yet we can probably all think of examples of people who seem to have "lost" their regional or national accent and of others whose accent stays firmly in place.

Given the personal and social importance of how someone speaks, why would anyone's accent change?

You may think of your accent as a physical part of who you are - but a conscious or subconscious desire to fit in can influence the way you speak, whether you want it to or not. Research has shown a person's accent will move towards that of the group of speakers with which they identify at some stage in their lives. Accents are a fluid feature of speech. If someone moves from Australia to the US to work, for example, they will probably at least modify their accent, either consciously or unconsciously.

This may be out of a need or desire to be more clearly understood and to be accepted in a new community. They might also want to avoid ridicule for the way that they speak. Over a quarter of senior professionals from working-class backgrounds in the UK have been singled out for their accents at work.

A sense of belonging

For people whose accents do shift, the way they speak may be less important to their sense of identity, or their identity with a social or professional group may be more pressing.

Even before we are born, we are exposed to the speech patterns of those around us. Studies of newborns have found that it is possible to detect tonal aspects specific to their speech communities from their cries. To have our needs met, we are more or less programmed to fit in. We produce vocalisations that sound like they belong to our caregivers' communities. We progress through various stages of speech development that result in us having speech patterns similar to those around us.

Emerging into society, we mix with people outside our limited social group and are exposed to more patterns of speech. This can result in a child's accent changing rapidly to be accepted by their peers. A colleague of mine from the US, for example, who works in the UK, told me how their child had begun to speak with a standard southern English accent since starting school. The parents were now being taught by their child to speak "correct" English.

A strong identity

For others whose accent does not seem to change, it could be because they feel secure in their identity, and their accent is very much part of that identity - or that preserving the difference is valuable to them. They may not even be aware of how much their accent means to them. If a speaker has what most deem to be a desirable accent, they might not want to lose the advantage by modifying it.

Whether consciously or not, people have at least some control over their speech when they move home. But brain damage or stroke can, in rare cases, result in foreign accent syndrome (FAS). This syndrome results from physical changes that are not under the speaker's control. Some areas in the brain are associated with producing and perceiving language, and we also have brain regions that control the motor aspects of speech.

If these are damaged, speakers may lose the ability to speak at all or experience changes in the way they articulate sounds because the motor area is sending different instructions to the vocal organs. An extreme example, reported recently in The Metro, describes how a woman, Abby French, from Texas, US, woke up after surgery with foreign accent syndrome.

French claimed that she sounded Russian, Ukrainian or Australian at any one time. Listeners tend to guess at the accent they think the changed speech sounds most like.

In some cases, listeners might discriminate against a person with FAS as they believe them to be foreigners, which shows how much our speech can influence how others treat us. It's no wonder many people unconsciously protect themselves by adapting their speech to those around them.

Author: Jane Setter - Professor of Phonetics, University of Reading