Though there are multiple factors that can influence native and second language acquisition, I have selected one of each to discuss, per the requirement. First, a biological factor that influences language acquisition is the age at which an individual acquires language. The mechanisms of the brain itself vary greatly with age, and though scientists generally agree that the critical time for language acquisition is early in life, there is not a perfectly defined ‘window’ of that timeline (Kuhl, 2010). The plasticity of infant brains is unmatched and the systems in place can acquire any language using auditory or visual cues (Kuhl, 2010). Kuhl (2010) suggests that the architecture of the infant brain allows for better detection of “phonetic and prosodic patters of speech” (para. 22). If the infant is introduced to more than one language, their brain ‘neural architecture’ allows for the patterns of more than one language (Kuhl, 2010). However, if they are introduced to only one language, then their brain will have a harder time as they grow older trying to allow for patterns that do not conform within the single language architecture of their brain (Kuhl, 2010). A child that is raised in a household that speaks only English will struggle as an adult to define sounds, words and sentences from another language that does not follow the same phonetic rules as the English language. However, a child raised in a bi- or multi- lingual household will have a brain that is more apt to understanding the different phonetic patterns of different languages and therefore will be more likely to have the ability to acquire a new language.
To speak to the window of language acquisition, I grew up in a predominately English-speaking household. My father only speaks English, though my mother speaks Dutch and I would hear it whenever she spoke to her relatives on the phone, or when they visited. However, it was not until grade one that I had any formal language training in a language that was not English. When I entered grade school, my parents put me in French immersion and therefore I spent half my days speaking French. Though I never heard or learned French throughout my infancy, my young brain was still malleable enough to adapt to learning another language. However, even though I learned French 50% of my days for my entire school career, I would only describe my skill level to be a medium proficiency. It is most certainly not my native language, however when I use it more frequently (for example when we spend time in France for a couple weeks) it tends to become more ‘available’ and easier. Though I cannot say for sure, I would think that if I was raised in a bilingual household (French/English) as well as attended French immersion as I did, my French language skills would be as advanced (or almost as advanced) as my English language skills. As this language was not introduced until early childhood, or used in the family home, I learned it later and therefore do not speak it as a native French speaker might.
An environmental factor that may influence the acquisition of language is the overall main language of the environment an individual grows up in. Whether an individual is raised in a predominately English/Spanish/Japanese etc. speaking environment will affect how they experience and/or perceive any language they hear (Diehl, Lotto & Holt, 2004). Infants prior to the age of one can distinguish sounds that identify with the language they have become accustomed to (Diehl et al., 2004). If an infant is exposed to a secondary language within their first year of life, then it can be assumed they will adapt and become able to distinguish sounds from the secondary language, as well as the first.
An example of this is one I can draw from my own experience. I was raised in an English-speaking household. However, from infancy, I was exposed to Dutch, as it is my mother’s native language. Though I was not formally taught to speak it, I can distinguish the sounds within the Dutch language in more complete ways than I could in another language I was not exposed to with regularity, such as Japanese. Though I do not speak Dutch, upon hearing it I can usually determine the general gist of the conversation being had. When spoken to in Dutch, I can usually understand enough to reply, though my reply will be in English.
Reference:
Diehl, R. L., Lotto, A. J., & Holt, L. L. (2004). Speech perception. Annual Review Psychology, 55, 149–179.
Kuhl, P. K. (2010). Brain mechanisms in early language acquisition. Neuron, 67(5), 713–727.
