Language and the brain
There are a bunch of conditions that affect how the brain handles language. The ones that are reasonably well understood relate to damage to specific parts of the brain or are genetic in origin, but there are others where we don’t know the cause. They all suggest interesting and complex things about the way our brains process language.
Category 1, the well known ones resulting from small areas becoming damaged in the brain, include Wernicke’s aphasia where the sufferer speaks apparently fluent gibberish, and Broca’s aphasia where speech is stumbling (because the damaged brain area helps control the speech organs) and rather agrammatical, but remains pretty comprehensible.
Genetically determined conditions include Specific Language Impairment where the grammatical rules are not learnt at all, so sufferers have no clue what the present participle of ‘take’ might be and are as likely to guess at ‘takement’ or ‘takesh’ as ‘taking’ – all cases have to be memorised individually. They also struggle with fitting the right version of words in sentences, frequently using plural and singular wrongly. Williams Syndrome sufferers go the other way, and have great difficulty learning that the past tense of ‘I take’ is not ‘I taked’, and they also struggle to find the exact word, using ‘wolf’ when they should say ‘dog’ and so on.
But there are all sorts of odd ones that, as far as I know, are not at all well understood. Bilingual people have been known to lose one language but retain the other, which sound comprehensible enough, but then they flip and only the other is available to them, then back again. Some have lost the understanding of verbs but not nouns – even when they are the same word. Some can read but not write, or write but not read even what they have written. One man suffered the loss of the odd but very limited set of words for fruit and vegetables.
I find all this dizzying, every case suggesting some new way that language might work in the brain, some added complexity to how language is constructed and understood – and maybe casts more doubt on Chomsky’s belief in a Universal Grammar hardwired into all human brains: surely these imply a greater degree of variation and complexity than that requires?