There is some overlap between the theories of first language acquisition (L1A) and second language acquisition (L2A), but they are not entirely the same . The process of L1A is unique to each individual and largely innate, while L2A involves building on previously learned linguistic knowledge and applying it to a new language. Additionally, L2A can involve conscious effort and instruction from teachers, whereas L1A typically occurs naturally without explicit instruction. However, many of the same linguistic principles and cognitive mechanisms that apply to L1A also apply to L2A, such as the role of input and the influence of cognitive and social factors on learning.

Salam Kouider, I agree with what previously written by Ajit.

Regarding the text of your question, could you clarify me which is the same information being repated in both theories of L1 and L2 ?

generally speaking, I would give a tell-tale example : when you learn a L2 after the critical period ( meaning after 6 years old) you will always have an accent while speaking in L2. For instance a French learning English as L2 since his primary school education will always tend to put a stress on the final syllable, and this is an uncoscius process : any given speaker of a L1 automatically tranfers the sound patterns and the phonological/prosodic rules of his L1 on the L2. The same hold for Arab speaking French as L2 : they will rather uncosciusly say "Andria" instead of "Andrea because the vowel /e/ is not part of the phonetic inventory of Arab language and so it is pronounced to its closest neighbour vowel /i/ .

While a child born in a Arabic/French speaking family will not have an accent whil speaking any of the two languages : he will not automatically put the stress on the word final syllable while speaking Arabic and viceversa he will be able correctly perceive and pronounce the /e/ .

So, there are differences and similarities beween L1 acquisition and L2 learning, and I would say that the best way to spot them is to look for case studies.

I would recommend this article highlighting the role of input in L1A https://scholar.google.com/citations?view_op=view_citation&hl=en&user=A-KZ0DwAAAAJ&citation_for_view=A-KZ0DwAAAAJ:SeFeTyx0c_EC

as well as these meta analysis articles https://www.finchpark.com/courses/tkt/Unit_12/child-l2-adult-l2.pdf

and a case study https://www.cambridge.org/core/journals/studies-in-second-language-acquisition/article/what-causes-avoidance-in-l2-learning/FAAF95C18AB86FA0F7A400AF94CFE622

Best,

Andrea

Hi Kouider Makhlouf

No, the theories of First Language Acquisition are not the same as those of Second Language Acquisition. While there are some similarities between the two processes, such as the importance of exposure to language input and the role of cognitive processing, the differences in context and learner characteristics mean that the theories of L1A and L2A are not the same.

I recommend these two very important references:

Pinker, S. (1994). The Language Instinct: How the Mind Creates Language. HarperCollins.

Ellis, R. (2008). The Study of Second Language Acquisition. Oxford University Press.