Listening is the first of the four language skills. It is usually the first language skill that we learn. In order to become a fluent speaker in any language, we need to develop strong listening skills. Listening not only helps us understand what people are saying. It also helps us to speak clearly to other people. If we are not in the right environment we will not be able to improve the level of our language. Therefore, I would say that the environment plays a fundamental role in the field of second language acquisition. To practise is the key to speak any language successfully, efficiently, effectively and fluently. Without practise , no one can acquire the competence of any language. Exposure to the language being learnt is very necessary. If there is no much opportunity to practise the language being learnt in the daily life situation, the acquisition process will be very much difficult. The process of practise can be very much successful if listening takes place in the right environment.

I would say, it depends a lot on how society views the other language. If the language provides a higher social status, as for example the knowledge of English here in Taiwan, children will learn the language of the parent that speaks this language, because it will often hear that it is great to learn the language. But if for example the mother comes from Vietnam, the child will most likely learn the language at an early age, but latest when starting schooling, stop speaking the language. Furthermore, it also depends if the other parent speaks the 'foreign' language, because if the child realizes that, e.g., the (foreign) mother uses the local language with the father, it will less likely answer in the foreign language, when talking to his/her mother because the local language will be the stronger language. 

I do not agree with Michela that a multilingual child is likely to receive less input from any of the languages she is acquiring. My kids are all bilingual, the eldest even trilingual. Chinese is their strongest language and you will not notice any difference between their Chinese ability and the one of their classmates. They did not receive less input for that language. When my eldest daughter was at high-school, her Chinese teacher wondered why the Chinese of the three children who had one foreign parent in the class was better compared to all of the other children whose parents were both from Taiwan.

They received less input from my language - for sure - but not from the language of the environment, although I never spoke Chinese to them.

I would say that the environmental effects that you ask about are the same as for monolingual children: if there’s no input, there’s no output, and if a language variety (language varieties being what we all learn) is deemed as lacking in prestige, there will be no incentive to use it.

These blog posts of mine expand on these issues:

The trick is in the input

http://beingmultilingual.blogspot.com/2011/10/trick-is-in-input.html

Little multi-dialectals

http://beingmultilingual.blogspot.com/2012/05/little-multi-dialectals.html

People see, people do

http://beingmultilingual.blogspot.com/2011/06/people-see-people-do.html

Madalena

I totally agree with Madalena. I would like to add concerns on a child moving from his more "civilized" country to lesser civilized one: would he feel ashamed of his culture? Some other aspects are his age and education. For example; 3 y.o. and no education; or, 10 y.o. and and outstanding role in primary school.

This does not perfectly address your question, but I just had an article published that addresses the overall environment of foreign language learning. It may have some ideas for you. Unfortunately, copyright does not allow me to share the full text on ResearchGate.  Here is the abstract:  

https://www.researchgate.net/publication/266557845

Article Environmental factors affecting Computer Assisted Language L...

Nhidal,

One should consider if the Bilingualism is a "rich bilingualism" (as the one of an American child studying at any American school in some other place in the World) or a "poor" one (like the one experienced by Deaf children in bilingual school, even when Bilingualism is official in the country.)

We have been working  within a bilingual deaf children school and we have learnt that prejudice exists, EVEN FROM THE SAME TEACHERS WHO ARE SUPPOSED TO BE THE ONES TO PROMOTE THEIR STUDENTS KNOWLEDGE CONSTRUCTION PROCESSES.

By the way, this coin has two sides. In that same school, an excellent deaf teacher who had got her deafness aged 16 was exposed to double prejudice: from non deaf teacher, since they consider their students cannot learn - in this way lowing their children horizon (...) and from deaf ones, since her sign language, as her second one, was not fluent.

Referring to the raeding and writing acquisition process, one of the hypotheses for the spread difficulties is that Oralism, the classical method, is not adequate for certain communities. This has been proved at least within young people living in risk situation and within deaf children, for which learning to read and write without listening at the oral referents is completely arbitrary. This is the reason by which we have learnt the Direct Way of reading and writing teaching-learning and applied it  for deaf children. IT WORKS.

The high relevance of environment in reading and writing acquisition was also the mais reason for deaf communities demanding for bilingual schools for deaf children, that our Brazilian Goverment, in the waves of Social Inclusion, was about to close. No deaf child can learn sign language in a place where he is the only one who uses it. In that kind of environment, he has no reference, and, additionally, he is deprived of language social functions, the most important for Socio-interactionists like us.

Obrigada, Laura, for spelling out so forcefully the prejudices surrounding language uses in Deaf communities! Multimodality is often forgotten in discussions of multilingualism.

I can't resist mentioning here yet another blog post of mine, 'Sign-speech multilinguals':

http://beingmultilingual.blogspot.com/2014/09/sign-speech-multilinguals.html

Madalena

You are wellcome, Madalena Cruz-Ferreira!

By the way, where are you from?

I will look carefully at your work.

Yours,

Laura.

Family is usually the main social unit that is responsible for nurturing bilingualism. However, external factors also play an important role within this environment for bilingual development. Particularly important is a stable and predictable linguistic environment. Simultaneous bilingualism involves the development of two languages learned parallel to each other, and this presupposes conscious effort by parents to use each language acquired by a bilingual child. Children also do need constant exposure to different language situations - extended family members, their peers, and schools (such as heritage language schools) can facilitate and encourage bilingualism. It is through these social interactions that a child shapes its own internalization of language and should extend it to a context outside the family. For bilingualism to be successful, it is also important that there is a positive attitude toward it within the larger social environment.

I agree with what the colleagues said earlier: environment is crucial.  Just to expand a little on the second part of your question: psychological factors are equally important, and as parents a little manipulation can be very beneficial.  My daughter grew up with 4 languages (Dutch with her mother, French with me, English in the environment, Urdu at the child minder - a language she lost after moving to nursery school).  Because my wife and I speak Dutch at home, French was the real minority language.  I enrolled my daughter in a French club aged 4.  She was pleased to see that other children were struggling to learn a language she already knew, and she realized that knowing French was something desirable in London. It boosted her French, linguistically and well as psychologically. It may have contributed to her continued use of the language. 

Check out: http://www.multilingualliving.com/wordpress/wp-content/uploads/free_downloads/MLM_JMDewaele.pdf

And her own take on her multilingualism:

http://www.multilingualliving.com/2013/04/29/trilingual-sixteen-quadrilingual/

The environment of the classroom, home and community contribute much to the process of 2nd language acquisition.  I did a study on new immigrant students from Mexico in two high schools in California on their bicultural development and second language acquisition.  One of the findings was students experienced much negativity about their lack of English proficiency coming from the teachers and students causing much tension in their minds.  They held a very negative attitude about becoming an American and English proficient.