In order to answer this question with regards to cognitive development and socio-cultural factors, I found about 42 research article. I analyzed them and translated to Persian. Now I am at the stage of coding, but I do not know how to draw a coding map in order to answer the question.
I found codes such as:
1. teaching Foreign language to young children
2. teaching a foreign language to older children
3. the impact of the first language on the second one
4. critical period
5. pronunciation
6. grammar
7. bilinguals
8. cultural issues
9. social issues
10. .....
I would really appreciate those who can help me in this regard.