When U.S. soldier Bowe Bergdahl was released after being held captive by the Afghan Taliban for five years, his father said his son was “having trouble speaking English.” Many will find this statement incredible: Is it really possible to forget your native language?
The answer depends on many factors. The first is what we mean by “forgetting.” Would it, for example, be possible for a mother tongue to be completely forgotten, so that a person cannot understand, or even recognize it anymore? The answer is yes, but only if she or he lost contact with that language before puberty.
Studies of international adoptees show that they very rapidly and completely forget their mother tongue, even if they are as old as 8 at the time that they are adopted. As adults, they may no longer be able to recognize the simplest words of the language they had first learned, and if they try to learn it again, they have few, if any, advantages over novice learners.
But those who are older than 12-years-old when contact with their native tongue is interrupted will probably retain at least some proficiency for the rest of their lives. They will not only be able to communicate in this language and understand most of it, it will also be much easier for them to learn it again later on. They may have some problems accessing the correct words, they may become somewhat less fluent, and they may develop a foreign accent, but none of these will seriously impair their functioning in that language.
This is good news for Bergdahl and his family. Any problems that he may currently have, for example, remembering some English words, speaking with a foreign accent or making grammatical mistakes, are likely to be temporary and to disappear quickly — probably within weeks.
What other factors, then, might have caused these problems? While held in captivity, Bergdahl probably had very little occasion to speak or hear English. But how frequently someone uses his or her language plays a far smaller role for the maintenance of this language than one might think. Several studies have attempted to probe this, and all have found a complete absence of any correlation between frequency of use and degree of language loss.
These findings may appear counterintuitive, but they suggest that, for adult speakers, the native language has become so deeply entrenched and so frequently rehearsed that it will remain active in memory despite the fact that it is hardly used at all, sometimes for decades.
Pashto pushing out English
On the other hand, many people will know the phenomenon that when they try to learn a new language, other languages (their native language, or other foreign languages) will keep “butting in.” When trying to focus on the new language, the language learner will therefore have to repress or inhibit this knowledge very strongly, and once this has been done for any length of time, it can then become harder to switch back to the language that has been so actively inhibited.
If Bergdahl made a very strong effort to learn Pashto, and if he was encouraged or even forced by his captors not to use English, that may therefore now account for some of the troubles he is having. Again, any such problems are like to be temporary and vanish within, at most, a few weeks.
Traumatic experiences may also be a factor when it comes to forgetting or suppressing a language. In the absence of information about what happened during Bergdahl’s captivity, we can only speculate on this, but it does seem a strong possibility that this may have played a part. In this event, it would probably be necessary to address the trauma itself, and not the linguistic problems that it might have caused.