Age as a Factor for Learning Language.
Age is a huge factor that must be considered when learning language. A first language that is acquired in adulthood might never be as fluent as language that is developed throughout childhood, and the same is similar for a second language acquired in the late teens and onward. A person might be able to read and write this second language fluently, but will almost always have problems with pronunciation. Second languages acquired in childhood, however, can usually be spoken fluently along with the first language.
First Language:
A first language is obviously the easiest to learn, and most easy to learn from childhood onward. Once adulthood is reached, language becomes much more difficult to learn as that person will forever have syntactic errors in their speech and they will more often than not be stuck in the telegraphic stage forever. Both parties want to use language to communicate with others, and they start in an almost identical way. A child isn't taught language through structure, but more through their own self-corrections, however an adult is and they may never fully develop their language skills in a way that allows them to become fluent.
Second Language:
A second language can be difficult or easy, depending on what age the learner is. A child will find a second language much easier to learn than an adult simply because they develop the same features (semantics, syntax, discourse, etc.) in both languages at roughly the same time, but also develop a wider lexicon and can produce sounds in both languages with relative ease (eventually). An adult who wishes to learn a second language may find it incredibly difficult as the language is structured and can't normally be developed on your own. They may have syntax and semantic issues forever and will never normally be able to grasp the phonological features of that language like a child can with ease.
Critical Period.
The critical period is a hypothetical construct time frame (usually three-ten years) that a child needs to learn language for them to be able to speak it fluently. Upon reaching the critical period, children are still able to learn a language's lexicon and basic grammar, but they will never be able to acquire the proper syntax to structure sentences correctly. After this critical period is over, it will be nearly impossibly to complete full sentences with the proper use of syntax. Language is very difficult to master after the critical and based on research, the person who missed their critical period tends to be stuck in the telegraphic stage and will forever struggle with most grammatical functions, therefore they will never truly be able to speak fluently.
Below is a video on Genie. She was discovered on November 4th, 1970 when her abuse came to the attention to the Los Angeles Child Welfare Authorities. This is one of the most severe cases of child abuse and neglect ever documented. She was isolated in her bedroom for 13 years and had absolutely no social interaction besides her father beating her and feeding her. Psychologists, linguists and other scientists found Genie's case as an opportunity to study acquisition of language skills and and linguistic development, and while she did develop new language skills, she was never fully capable of acquiring English grammar to the extent that the rest of us have.
Below is a video on Genie. She was discovered on November 4th, 1970 when her abuse came to the attention to the Los Angeles Child Welfare Authorities. This is one of the most severe cases of child abuse and neglect ever documented. She was isolated in her bedroom for 13 years and had absolutely no social interaction besides her father beating her and feeding her. Psychologists, linguists and other scientists found Genie's case as an opportunity to study acquisition of language skills and and linguistic development, and while she did develop new language skills, she was never fully capable of acquiring English grammar to the extent that the rest of us have.