Discuss the first language acquisition in children and second language aquisition in adults

Primary language development begins at age 5 and is complete by
puberty.

Here are the theories of primary language
acquisition:

Behaviorist Theory: Language is acquired through
enforcement and imitation, i.e.it is a form of operant
conditioning.

Nativist Theory: Humans have an innate language
acquisition device. Once vocabulary is learned, the learner has an innate ability to form
meaningful sentences.

Empiricist Theory: There is enough information
in what a child learns to allow development of the ability to communicate in proper sentences.
There is no need for an innate language acquisition
device.

Interactionist Perspective: This is a combination of
nativist and behaviorist theories.

Second language acquisition
follows the same steps in all adult students, but there is extreme individual variation in time
for each step. Also, upon acquisition of fluency, there will be a considerable variation in level
of fluency, writing ability, degree of non-native accent when speaking, and ability to enter
advanced fluency such as expressing and understanding sarcasm and
humor.

Stages of second language acquisition in adults are as
follows:

Pre-production: Student acquires a vocabulary of up to 500
words, but does not speak, yet can repeat what teacher says.

Early
production: This stage lasts approximately 6 months. The student has an active and repeatable
vocabulary of 1000 words. She speaks in phrases of a few
words.

Speech emergence: Vocabulary is 3,000 words. Student
communicates in simple phrases and sentences.

Intermediate fluency:
6,000 words. Student uses more complex sentences in writing and speech. At this stage the student
uses strategies from her native language to augment abilities in the second
language.

Advanced fluency: This takes 4-10 years. Student has a
near native skill in learning content, but needs assistance in studying history or social
studies, and some assistance in writing.