Introduction to Contemporary Linguistics October 7, 1998 Brain and language OVERVIEW: 1. The human brain 2. Left brain / right brain 3. The language areas of the brain 4. The evolution of language 5. A short video about the brain and language ============================================================= 1. The human brain >The human brain has been called the most complex thing in the universe, so don't be surprised if we don't very much about it yet. >There are two ways to study it: >Neurology: the study of the physical brain (related to neuron = "brain cell") >Neurolinguistics: the study of the relationship between the physical brain and the use of language. >Cognitive psychology: the study of the mind, which is what the brain does: it takes information input and outputs behavior >Psycholinguistics: the study of the processing (input and output) of language (more about this later) >The most basic fact of neurology: The brain is not made out of pudding. That is, it has structure. (OVERHEAD) >Cerebrum: the big, famous part of the brain. >Most of the processing is is done in the surface (cerebral) cortex, which is only 1.5-5.0 mm thick! >This is why the brain is wrinkled: it's so that this 830 cm2 cerebral cortex can be fit into your head! >The cerebrum is divided into two hemispheres (half spheres) that are connected only by a link in the middle (the corpus callosum) >The hemispheres are connected to the opposite of the body: the left hemisphere controls muscles on the right side of the body, receives input from the right ear and from the right half of the visual field. >Some special parts of the cerebral cortex: >Sensory and motor strips: along that central fold: for feeling and controlling muscles >Auditory cortex: near the (opposite) ear >Visual cortex: at the back of the cerebrum 2. Left brain / right brain >What you may have heard: >The "left brain" is rational and logical. >The "right brain" is spiritual and artistic, and may even represent "the mind of the Orient" that overly logical Westerners must learn to develop (??!) >What a scientist says (Sperry 1984): "One must caution ... that the experimentally observed polarity in right-left cognitive styles is an idea in general with which it is very easy to run wild.... It is important to remember that the two hemispheres in the normal intact brain tend regularly to function closely together as a unit." >The two hemispheres are not "specialized" for distinct functions; neither "dominates" the other; but some functions tend to be lateralized: processed more quickly or efficiently on one side: Left Right information about time information about space analysis into parts perception of wholes LANGUAGE >Lateralization of language is shown by experiments where different sounds are presented to each ear: >The right ear is faster at recognizing speech sounds (= left hemisphere, because of the opposite-side wiring) >The same thing can be shown visually: >Flash pictures on the left side of the visual field or on the right side; people will be faster to say what they are if they are flashed on the right side (=left hemisphere) >Split-brain studies: >To prevent epilepsy (random neural firings) from spreading from one hemisphere to another, the link used to be cut >However, if the two hemispheres cannot communicate, information processed in one side cannot interact with the other side >If you show split-brain patients an object in the left visual field (=right hemisphere), or put it into their left hand (=right hemisphere), they cannot name it >Remember that space is lateralized to the right hemisphere. But if space is used by a language (such as sign language), then it will be lateralized to the left hemisphere, just like the rest of language! >How ASL uses space: I-GIVE-YOU, HE-GIVE-THEM, etc... >With damage in the right hemisphere, ASL signers can still do this, though they can't draw accurate spatial maps. >So does everyone in this room process language on the left? >If you are right-handed, there is a 97% chance you have language in the left hemisphere >But if you are left-handed, the chance is only 68%; 19% chance you process language on the right; 13% chance you process language on both sides! >Your gender (sex) also affects where language is processed: >Women are more likely to process language on both sides than are men (OVERHEAD) >This is already true for 3-month-old babies, so it's probably an innate difference (but why??) 3. The language areas of the brain >Where exactly is language processed in the left hemisphere? >Much evidence comes from the study of aphasia: language problems caused by brain damage. >Broca's area: named after the French doctor who first discovered it (OVERHEAD) >Damage to this area causes Broca's aphasia: speech is agrammatic (without syntax or correct morphology), but the meaning can often be guessed by context: >Here a patient tries to explain about a visit to a hospital to get dental surgery: "Yes ... ah ... Monday ... er ... Dad and Peter [his name], and Dad ... er ... hospital ... and ah ... Wednesday ... Wednesday, nine o'clock ... and oh ... Thursday ... ten o'clock, ah doctors ... two ... and doctors ... and er ... teeth ... yeah." >So maybe Broca's area processes "grammar", especially syntax, morphology and phonology? >Broca's aphasics cannot produce sentences with syntactic structure. >They can't use syntax to get meaning, so they are tricked by their real-world knowledge: "The bird that the cat watched was hungry." (Who is hungry?) >Wernicke's area: named after the German doctor who discovered it (OVERHEAD) >Damage to this area causes Wernicke's aphasia: speech is fluent but makes no sense (including fake words: jargon aphasia): "Boy, I'm sweating, I'm awful nervous, you know, once in a while I get caught up, I can't mention the tarripoi, a month ago, quite a little, I've done a lot well, I impose a lot, while, on the other hand, you know what I mean, I have to run around, look it over, trebbin and all that sort of stuff." >Does Wernicke's area control semantics? "Wernicke's area seems to have a role in looking up words and funneling them to other areas, notably Broca's, that assemble ... them syntactically. Wernicke's aphasia, perhaps, is the product of an intact Broca's area madly churning out phrases without the intended message and intended words that Wernicke's area normally supplies." Pinker (1994:311) >How the different parts of the brain work together (OVERHEAD) >Where is the lexicon? EVERYWHERE! >Words seem to be stored all across the cerebral cortex, in both hemispheres. >Semantically related words are stored together, so brain damage in one spot might cause you to lose all words for vegetables, for example. 4. The evolution of language >People have suggested pretty strange theories for the origin of language. For example, in the 1600's, many European scholars thought that the first language must have been "perfect" (since it was taught by God to Adam), and therefore the first language must have been Chinese, since each character supposedly represents one unique idea (not really true!) >More scientific debate about language concerns the following questions: >Is the evolution of human language more like the evolution of culture, such as the change from hunting-and-gathering to agriculture to industrial society? >Or is it more like the evolution of our physical bodies, from small-brained animals to us? >We know for sure that something evolved, since animal communication systems are quite different from human language: they all have a very small "lexicon" and no grammar at all (no syntax, morphology or phonology): >Bee dances [OVERHEAD] >Monkey cries [OVERHEAD] >But what about those chimpanzees who learned sign language? (They didn't really learn it. More later.) >Here are some of the biological changes that created language: >Our tongues and other structures changed shape: Based on skull shape, Australopithicines (Africa, 3-4 million years ago) seem to have had much flatter tongues than us, so they couldn't make as many sounds. [OVERHEAD] >However, Neanderthals (Europe, 60,000 years ago) seem to have had the same size nerve bundle going to the tongue as modern humans [OVERHEAD] >What changes happened inside the brain are more mysterious; one guy thinks the brain "rewired" parts of the brain used for vision (primates like apes and humans are very visual). If so, maybe sign languages appeared before spoken languages! [MAGAZINE] 5. A short video about the brain and language >Ten minutes from The Mind: Language (1988). >Marcus E. Raichle (Washingon University School of Medicine): >PET scans showing what parts of the brain are active when people are reading words aloud. >Antonio R. Damasio (University of Iowa) >Aphasic patients are unable to process syntax correctly. >Neither researcher is a strong believer in modularity (the claim that certain parts of the brain are specialized just for language). 2 7