Three British men who suffered left brain damage that undermined their capacity to speak and understand language still possess a firm grasp of mathematics, a new study finds. This observation dramatically illustrates the presence of separate brain systems for language and numbers, at least in adults, say neuroscientist Rosemary A. Varley of the University of Sheffield in England and her coworkers.
The findings, however, are unlikely to resolve a long-running debate over whether children use language to develop their number sense. Some researchers argue that initial math insights arise from knowledge of the words for numbers or of grammatical rules for arranging words in phrases. Other scientists suspect that, from infancy on, language and math follow different mental and neural paths.
"I believe that dedicated brain mechanisms exist [from the start] for language and mathematics, but others on my team disagree with me" Varley says.
An account of the new investigation will appear in an upcoming Proceedings of the National Academy of Sciences.
The men who participated ranged in age from 56 to 59. Burst or injured blood vessels had damaged left brain tissue at least 3 years before the researchers tested the men's skills.
Participants exhibited little facility with language and were especially poor at grammar. They spoke only in single words and sentence fragments. Moreover, they couldn't distinguish the meanings of simple sentences with subject and object reversed, such as "The lion killed the man" and "The man killed the lion"
Yet each participant readily solved mathematical problems, including those that require applying number-combination rules that the researchers …