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Born Wordy

What gives humans the unique capacity for language?

Baby Talk

Initial views suggested that the size of our brains gave us the lingual advantage, but as I describe in an earlier blog post, brain size isn't everything. Instead, the answer may lie in our genes. Humans, it seems, share a genetic code which wires our brains for language.

The difficulty in solving the mystery of human language is wrapped in the deeper puzzle of how our brains work. Brains must somehow take the electric signals from our neurons, the specialized cells which make up our brain, and compose them into thoughts and conscious experiences.

One leading theory is that when neurons communicate, they form networks. As your neural networks get increasingly complex, your brain can accommodate increasingly complex thinking. Human's bulky brains tip the scales at 1300-1400 grams, whereas a chimpanzee brain amounts to a feathery 420 grams, in comparison. Each of the human's 100 billion neurons connects to 1000 others, providing a rich network that can comprehend weighty subjects like economics and algebra. Perhaps no other species' brain has the sufficient complexity for language?

However, some humans are born with a rare condition called microcephaly, where their brain develops to only a fraction of the normal size. Microcephalic's brains usually weigh in at 430-600 grams, similar to a chimpanzee. Whereas chimps can learn to repeat meaningful signs, they have never demonstrated the ability to grasp syntax. Microcephalics, even with extremely under-developed brains, have demonstrated a language knack comparable to a 5 year old. There are even cases of microcephalics growing up to become doctors. If the complexity of our brains alone can't explain our gift of gab, what can?

Although most humans learn a language, not everyone has the opportunity. In Nicaragua, for example, only recently did they have schools for deaf children. Prior to the late 1970s, deaf children were isolated from each other and were mostly limited to contact with their hearing families. They were only able to communicate at home using gestures and weren't exposed to grammar. In the late 70s, a school was built in the capital city of Managua and teachers were brought in to teach deaf children to sign. Although the children didn't learn a great deal from the teachers, remarkably, they began developing their own language on the playground and the bus rides home. Over the course of the next 20 years, the language became increasingly complex, and now has intricate grammatical elements which define language, such as verb conjugations for present, past and future tense.  Watch this fascinating documentary for an in depth look.

Yet, some deaf Nicaraguans who grew up before this school's existence still have trouble learning more than basic language skills, despite repeated attempts to teach them. The difficulty acquiring language after a certain age led researchers to believe that there may be a sensitive period where the brain is still plastic enough learn the rules of grammar. Beyond 12 years old, it becomes much more difficult to learn a language. If a child does not learn any language by this age, their brains may be too rigid to ever become fluent.

The story of the deaf Nicaraguan children offers another insight: humans may be genetically programmed for language. The first group of deaf children had no previous exposure to syntax, but, motivated by their innate desire to communicate, they developed one all their own and have been able to pass it on to younger schoolmates. This is the only documented example of a completely new language being born, but it could resemble how human's earliest language developed.

Further indicating our intrinsic ability to learn language, children around the world begin talking at about the same age, despite widely varied cultures and parenting styles.

If humans brains all share the same capacity for language, there must be some similarities in how our brains process language. Though not all languages' speakers code nouns and verbs in the same brain regions, there does seem to be a consistent region for grammar, the rules of your language. Whether you speak Swahili or Korean, the Left Inferior Frontal Cortex (LIFC), the region of your brain just above your left temple, is active as you process grammar.

Language Brain

Our brains seem programmed to learn language, something uniquely human. Although we have some clues, we have not uncovered the genetic code which gives our brain a grammar center. Until then, the search continues.

 

Notes:

Sakai KL. Language acquisition and brain development. Science. 2005 Nov 4;310(5749):815-9. Review.

Arshavsky YI. Two functions of early language experience. Brain Res Rev. 2009 May;60(2):327-40. Review.

Carreiras M, Lopez J, Rivero F, Corina D. Linguistic perception: neural processing of a whistled language. Nature. 2005 Jan 6;433(7021):31-2.

Morgan G, Kegl J. Nicaraguan Sign Language and Theory of Mind: the issue of critical periods and abilities. J Child Psychol Psychiatry. 2006 Aug;47(8):811-9.

 

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