Psychology: Essential Thinkers, Classic Theories, and How They Inform Your World - Andrea Bonior 2016

Paul Broca
Biological Psychology
The Canon

BORN 1824, Sainte-Foy-la-Grande, Gironde, France

DIED 1880, Paris, France

Educated at the University of Paris and the Hôtel-Dieu de Paris

BIG IDEA

Paul Broca’s impact on psychology was so significant that a section of the brain bears his name. Broca’s area, in the frontal lobe, is the part of the dominant hemisphere responsible for producing speech. (Most people are right-handed, and so in most people it’s the left hemisphere of the brain that is dominant, which means that Broca’s area, for most people, is in the left hemisphere.)

Broca’s association with this area of the brain began when, as a surgeon, he encountered a patient who had been hospitalized for two decades. The patient’s listening comprehension was solid—he could understand whatever was said to him—but he could speak only a single syllable. Broca examined the patient’s tongue, vocal cords, and voice box and quickly deduced that nothing was physically wrong with them. Shortly afterward, when the patient died, Broca conducted an autopsy and discovered a large lesion in part of the brain’s left frontal lobe. Broca’s biggest idea was solidified right then and there: Damage to this part of the brain has a unique and specific effect on the ability to produce spoken words, even though this damage to the brain doesn’t affect the ability to understand words.

Earlier theorists had attempted to put forth the idea of brain localization—namely, the notion that specific parts of the brain can be linked to specific psychological functions. Perhaps because they were theorists more than scientists, this idea had not gained currency in the prevailing scientific views of the time. But Broca’s discovery spurred him to further study—he analyzed the brains of a dozen more deceased patients and noticed similar lesions. He was finally able to back up the idea of brain localization with concrete, systematic, empirical evidence that gave this idea research momentum.

Broca’s original patient was suffering from what we now call aphasia, a term that refers broadly to a deficit in speech. The particular type of aphasia from which this patient suffered is called expressive aphasia, or now even Broca’s aphasia. For this patient, language function as a whole was not lost—recall his ability to understand what was said to him—but his ability to speak was greatly compromised by the lesion in his frontal lobe. In the decade after Broca’s discovery, a nearby area of the brain that accounts for language comprehension was identified and named for Carl Wernicke, a German neurologist. People who suffer from aphasia involving that area are able to talk fluently, but their utterances aren’t put together in meaningful ways, nor can they understand what is being said to them. Their condition is called receptive aphasia or now, often, Wernicke’s aphasia.

The discovery of such a clear correlation between the biological structure of the brain and particular kinds of abilities and behavior was momentous. It also confirmed that the brain is not a homogeneous structure but has different areas, each with its own characteristics. The latter discovery underlies much of brain research to this day.

THEN WHAT?

Broca’s findings set the stage for long-term research into the brain correlates of various emotions and psychological functions, and for the broader study of the physiological determinants of behavioral traits. This area of research continues to the present and includes projects as sophisticated as the mapping of the human genome. Broca’s findings also encouraged a key underlying element of physical anthropology—study of the implications of physical measurements of the brain.

WHAT ABOUT ME?

Broca’s discoveries, and brain localization more generally, are sometimes associated more with bad news than with good. Consider a brain tumor, to take a stark example. A brain tumor’s signs and symptoms can include an almost unlimited array of disruptions—memory loss, taste hallucinations, loss of balance, changes in vision, vomiting, muscular weakness—that affect sensations, behavior, emotions, and the personality as a whole. The fact that there is no single standard symptomatology for brain tumors can sometimes be problematic from the standpoint of early diagnosis, since a person can easily brush aside the symptoms of a brain tumor. (It’s also true that someone can be convinced of having a brain tumor when there’s nothing wrong with the brain at all.)

Brain injuries, too, can have immediate and distinct consequences—trauma to the head can cause symptoms that vary widely according to which part of the brain has borne the brunt of the impact. In this respect, the most famous case, involving a railroad construction worker named Phineas Gage, predated Broca’s discovery by 13 years. In 1848, Gage suffered a horrifying injury on the job when an iron rod penetrated his left cheek, pierced his skull, and emerged from the crown of his head. Gage survived and even recovered from the injury, but his personality was forever altered. The personality changes were not unexpected, of course, but they appeared to go beyond the emotional trauma of the injury. Before the accident, Gage was productive and organized, but now he became unpredictable and incapable of initiating plans or following through on them. Once mild-mannered, he now cursed up a storm. He became impatient, stubborn, and unable to work with others. The damage sustained by his brain changed his personality completely.

Even more fascinating are cases of foreign accent syndrome, which can appear after a brain injury or even after a severe migraine headache. The person affected by this syndrome starts speaking in unusual ways, and his or her previous pitch and cadence are significantly changed. This is not to say that someone with this syndrome necessarily speaks with the precise accent associated with specific foreign speakers, but rather that there is a striking alteration in voice mechanics. Research points to damage within the cerebellum, the part of the brain that controls motor movement, and to a misalignment between the jaw and the tongue so that words are uttered in a way entirely different from the person’s previous speech patterns.