“The carotid?”
“Yeah. Yeah. But…
“Go on,” I said, “Tell us more.”
“It’s
“Are you right-handed or left-handed?”
“Right-handed.”
“Can you write with the left now?”
“Yeah.”
“Okay. Good. What about word processing?”
“Processing
“But when you write, is it slow?”
“Yeah.”
“Just like your speech?”
“Right.”
“When people talk fast you have no problem understanding them?”
“Yeah, yeah.”
“You can understand.”
“Right.”
“Very good.”
“
“Okay, do you think your speech is slowed down, or your thought is slowed down?”
“Okay. But
He then made twisting motions with his mouth. Presumably he meant that his flow of thought felt intact, but the words were not coming out fluently.
“Supposing I ask you a question,” I said. “Mary and Joe together have eighteen apples.”
“All right.”
“Joe has twice as many apples as Mary.”
“Okay.”
“So how many does Mary have? How many does Joe have?”
“
“Mary and Joe together have eighteen apples…”
“Six,
“Excellent!”
So Dr. Hamdi had basic conceptual algebra, was able to do simple arithmetic, and had good comprehension of language even for relatively complex sentences. I was told he had been a superb mathematician before his accident. Yet later, when Jason and I tested Dr. Hamdi on more complex algebra using symbols, he kept trying hard but failing. I was intrigued by the possibility that the Broca’s area might be specialized not just for the syntax, or syntactic structure, of natural language, but also for other, more arbitrary languages that have formal rules, such as algebra or computer programming. Even though the area might have evolved for natural language, it may have the latent capacity for other functions that bear a certain resemblance to the rules of syntax.
What do I mean by “syntax”? To understand Dr. Hamdi’s main problem, consider a routine sentence such as “I lent the book you gave me to Mary.” Here an entire noun phrase—“the book you gave me”—is embedded in a larger sentence. That embedding process, called recursion, is facilitated by function words and is made possible by a number of unconscious rules—rules that all languages follow, no matter how different they may seem on the surface. Recursion can be repeated any number of times to make a sentence as complex as it needs to be in order to convey its ideas. With each recursion, the sentence adds a new branch to its phrase structure. Our example sentence can be expanded, for instance, to “I lent the book you gave me while I was in the hospital to Mary,” and from there to “I lent the book you gave me while I was in the hospital to a nice woman I met there named Mary,” and so on. Syntax allows us to create sentences as complex as our short-term memory can handle. Of course, if we go on too long, it can get silly or start to feel like a game, as in the old English nursery rhyme:
Now, before we go on discussing language, we need to ask how we can be sure Dr. Hamdi’s problem was really a disorder of language at this abstract level and not something more mundane. You might think, reasonably, that the stroke had damaged the parts of his cortex that control his lips, tongue, palate, and other small muscles required for the execution of speech. Because talking required such effort, he was economizing on words. The telegraphic nature of his speech may have been to save effort. But I did some simple tests to show Jason that this couldn’t be the reason.
“Dr. Hamdi, can you write down on this pad the reason why you went to the hospital? What happened?”
Dr. Hamdi understood our request and proceeded to write, using his left hand, a long paragraph about the circumstances that brought him to our hospital. Although the handwriting wasn’t good, the paragraph made sense. We could understand what he had written. Yet remarkably, his writing also had poor grammatical structure. Too few “ands,” “ifs,” and “buts.” If his problem were related to speech muscles, why did his writing also have the same abnormal form as his speech? After all, there was nothing wrong with his left hand.