How much does our capacity to solve complex problems depend on our language ability? That's been one of the perennial questions for big thinkers from philosophers to neuroscientists. Now, research involving three brain-damaged men may be providing some answers.
Mathematical equations often share properties with grammatical sentences. For example, both can use embedded phrases: In the sentence, "the fox, which was quick and brown, jumped over the lazy dog", "which was quick and brown" is an embedded phrase. Likewise, in the equation 90-[(3+17) x 3], the numbers in parentheses and brackets are embedded. But experts differ on whether both tasks utilize the same fundamental brain processes. Some brain imaging studies have shown activation of speech areas during mathematical tasks, while others have not.
To cast more light on the question, a team led by Rosemary Varley at the University of Sheffield in the U.K. administered a variety of tests to three men with brain damage in their language processing centers. The condition causes aphasia--an impairment in the ability to understand words. Researchers asked the men to add, subtract, multiply, and divide, as well as perform more complex problems with structures analogous to language structures that they were no longer able to use.
As expected, the men had great difficulty understanding complex grammar, including embedded phrases in sentences. They also had a hard time comprehending numbers when they were written as words. But the men did just fine with the mathematical equations, even those with embedded elements.
The authors say the results suggest that even if language in early life provides a "template" that facilitates math learning, it appears that by adulthood, mathematical thinking can stand on its own. They report their findings online this week in the Proceedings of the National Academy of Sciences.
The study offers "a powerful new argument" that the syntax of arithmetic and language are independent, at least in the adult brain, says neuroscientist Brian Butterworth of the University College London. But that does not rule out the notion that both syntax and math abilities derive from a deeper common architecture, says cognitive psychologist Stanislas Dehaene of the Service Hospitalier Frédéric Joliot in Orsay Cedex, France.