When we learn to speak a foreign language as an adult it is practically impossible to lose our original accent. If you think of people you know who speak English as a foreign language, sometimes to highest of standards, there is always something that gives them away: a slight lilt, one particular sound they mispronounce or some awkwardness of expression which tells us that they are not English speakers from birth. The same of course is true of those of us who like to think we speak very good Spanish. No matter how good we may become we will never be able to fool native Spanish speakers, even if we can fool our compatriots, that we can truly speak Spanish like a native.
There are several reasons for this, the most fundamental being to do with how our language learning skills develop in early childhood. As we start to distinguish and imitate the sounds we hear around us our speech organs: that is our throat, mouth and tongue, develop in such a way as to mimic these sounds perfectly. If we are lucky enough to be exposed to more than one language from very early childhood, this process will allow us to echo back all the sounds we hear from different sources. There are also more complex processes that occur in the brains of true bilinguals which relate to other cultural and linguistic factors.
As children grow they lose this plasticity and although the maximum age at which a child can truly imitate a native accent is variable, it is possible that children as young as three or four are sufficiently formed in their native tongue to be unable to achieve perfect pronunciation in a second language. Of course, a lot depends on how much exposure the child receives to the second language and what his or her dominant cultural references are. This leads me to the second, and perhaps more interesting, reason why some people’s accents are stronger than others.
In the case of older children, adolescents and adults learning a new language there is an issue of self-image, often working at an unconscious level. We may be reluctant or even afraid of losing our identity and clinging to our accents can be a way of asserting ourselves as different from those around us. This might sound a bit fanciful and would take more time to explore and explain, but for now I think it´s an interesting thought to ponder: how much of our accent is dictated by our fear of letting go and sounding too foreign?