TALKING TO EACH OTHERLanguage and the brain
The most widely known fact about language processing is that, for most
people (over 95 percent of right-handers and 60 percent of left-handers),
it is predominantly performed by the left hemisphere. More detailed
clues as to how the brain processes speech come from two sources – the
study of patients with brain damage, and from recording people’s brain
activity while they’re engaged in language tasks.
Speech problems that arise as a result of brain damage are known as
aphasia, and there are two main types – fluent and non-fluent. Fluent or
“semantic” aphasia – characterized by garbled, flowing speech conveying
little concrete information – tends to follow damage to the temporal lobe,
near its junction with the parietal lobe (Wernicke’s area). By contrast,
non-fluent aphasia – characterized by staccato speech with few verbs or
little use of grammar – tends to occur after damage to the Broca’s area in
the frontal lobe (see p.41). Stated crudely, these impairments suggest that
language functioning is divided into two specialisms: Broca’s area for
processing syntax, and Wernicke’s area for decoding meaning.
Other clues about language-processing come from patterns of dyslexia
acquired through brain damage. Some patients develop phonological
dyslexia, which means they have difficulty translating letters into sounds.
This affects their ability to read new words that they’ve never seen before.
The linguist Noam Chomsky has argued that all human infants have a built-in
language faculty and that all languages are underpinned by a universal grammar.