Exploring Language in Humans (Part Two)

The visual cortex is a region of the human brain located in the posterior and medial portions of the occipital lobe. As the name implies, it is responsible for processing visual stimuli. It works in tandem with the retina and, as evolution would have it, it is composed of various subregions which are "equivalent to particular points in the visual field of the eyes" (Raven, 2005). In Geschwind's sequence of reading aloud, the visual cortex of the brain is the first to receive information from the retina. It does not meaningfully interpret this information, however. The information is transformed and communicated further via the angular gyrus. The angular gyrus is located in the parietal region of the human brain. From there, an auditory code is established, and this code is transcribed and received in another visual association area in the left temporal lobe. This region is called Wernicke's area, after the German physician Karl Wernicke (1848-1905), and it interprets the code of the angular gyrus and makes sense of what we see. Just as damage to the retina could result in the inability to see, damage to the temporal lobe may result in the inability to understand the written words of others:

"It is remarkable and significant that brain-damaged patients can be completely competent in spoken language and entirely incompetent in written language, or vice versa. They may be able to write but unable to read; able to read numbers but not letters; able to name objects but not colors" (Sagan, 1977).

The capacity to process the sounds of language is similar to that of visual processing. Sounds are first imparted to the inner ear and transmitted to the auditory cortex in the temporal lobe. Similar to visual stimuli, auditory sounds are then reorganized in association areas following the initial, auditory stimulus. It must be remembered that since humans are a species that learn from their environment, how sights and sounds are interpreted can vary from individual to individual and from group to group. Our responses are molded and manufactured by means of a unique genetic disposition that is furthered influenced by our life histories. (1) As a species, humans use "past visual experiences to interpret visual stimuli (color, form, and movement)" just as they use memories of sound (pitch, rhythm, and intensity) to glean subjective meaning form the world about them (Marieb, 2004). Beauty is truly in the eye of the beholder, in this regard. Further, the ability to make elaborate, cognitive sense of our environment influences how we interact with each other. It results in a cross-communication between individuals that can be quite versatile and elaborate:

"All human societies possess language, and there are said to be as many as six thousand languages actively spoken in the world today, though most are hanging by a thread. The vocabularies from which these languages are built can vary widely, as can the vocal gymnastics demanded and the logic that governs their use" (Tattersall, 1998).

Whether language is an adaptation towards survival, or a cognitive function that enables little more than idle chatter, it is worth mention that nonhuman primates appear to have the same capability:

"For example, vervet monkeys give different warning calls for different predators. When they hear the "leopard" call, vervets climb trees and anxiously look down; when they hear the "eagle" call, they hide in low bushes or look up" (Cartmill, 1998).

In spite of the apparent similarity between humans and vervet monkeys, there are differences in the way in which both visual stimuli and auditory stimuli are translated. For example, in relation to visual processing, "recent experiments on monkeys indicate that complex visual processing involves the entire posterior half of the cerebral hemispheres" (Marieb, 2004). This is surely the result of the lack of specialization in the "lower" primate brain, and it implies that our enhanced ability to create and interpret meaning is due to the relatively increased amount of localization:

"Although the vervet's leopard call is in some sense about leopards, it isn't a word for leopard. Like a frog's croak, its meaning is strictly instrumental; it's a stimulus that elicits an automatic response. All a vervet can "say" with it is "EEK! A leopard!" - not "I really hate leopards" or "No leopards here, thank goodness" or "A leopard ate Alice yesterday" (Cartmill, 1998).

As mentioned, Broca's area is directly responsible for coordinating and manipulating the muscles that enable language to be spoken. From this region of the cerebral cortex, we now turn away from the human brain and explore the anatomical specializations of the throat and mouth that make language possible: the larynx, the pharynx, and the tongue...

(1) Noam Chomsky "concluded that the deepest structures of language are innate, not learned. We are all born with the same fundamental grammar hard-wired into our brains, and we are programmed to pick up the additional rules of the local language, just as baby ducks are hard-wired to follow the first big animal they see when they hatch" (Cartmill, 1998).

References

Cartmill, M. (1998, November). The Gift of Gab. Discover, 56, 58, 62-64.

Marieb, E. (2004). Human Anatomy and Physiology. San Francisco: Pearson.

Raven, P. (2005). Biology. New York: McGraw-Hill.

Sagan, C. (1977). The Dragons of Eden. New York: Random House.

Tattersall, I. (1998). Becoming Human. Orlando: Harcourt.