HowStuffWorks 2008

How Humans Process Language

Two primary theories explain how our hominid ancestors began speaking. The vocal theory proposes that primates' innate vocalizations evolved into speech thanks to changes in the structure of the mouth and larynx and the enlargement of the brain [source: Dubuc]. The gestural theory, on the other hand, describes language as a step up from manual communication. Bipedalism freed our hands for signaling, then talking liberated our hands for other tasks [source: Dubuc].

Today, language fundamentals begin in the fetal stage. Studies have found that fetuses can differentiate between male and female voices and recognize novel syllables [source: Dubuc]. After birth, infants babble, imitate sounds and gradually string together familiar syllables, often saying their first words around 10 months [source: Dubuc].

Once we have the gift of gab, what's going on upstairs when we verbally express ourselves, and how do humans process language? The speech centers in our brains are Broca's area and Wernicke's area. Broca's area in the left frontal cortex controls language production, and Wernicke's in the posterior temporal lobe analyzes the words you see and hear and also places those words in the correct order before you speak.

Of course, these areas of the brain don't function in isolation. Imagine that someone asks, "How are you?" Once that message travels through the ear, the electrical impulse from the vibration enters the primary auditory cortex, which figures out that the source is a human voice. Then, the information moves to Wernicke's area for interpretation, followed by Broca's area where you select the words for a response. That message then goes to the primary motor cortex that signals your larynx and mouth to vocalize, "I'm fine, thanks" [source: Chudler].

One portion of tissue in Wernicke's area -- the planum temporale -- has been called our "language center" since it plays an integral role in comprehending the speech that we hear [source: Blakeslee]. This region is highly asymmetrical in most people's brains, causing a bulk of it to reside in the left hemisphere. The planum temporale's odd shape was once believed to be exclusive to humans. In 1998, three anthropologists and a neurologist shook up that notion [source: Blakeslee]. Guess which nonhuman primate they discovered had the same oddly shaped planum temporale? You guessed it: chimpanzees.

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