Psycholinguistics: A Resource Book for Students PDF

52 D EV E LO P M E NT L O C A L I S I N G LA N G U A G E I N T H E B RA I N 53 vervet troop clearly understand these calls as they respond in an appropriate way: Consider this: shou...

52 D EV E LO P M E NT L O C A L I S I N G LA N G U A G E I N T H E B RA I N 53 vervet troop clearly understand these calls as they respond in an appropriate way: Consider this: should we be trying at all to compare animal communication with our [0 Activity 1 jumping into a tree to avoid a leopard, jumping out of a tree when an eagle is. own? Or should we be looking for other criteria to judge its effectiveness? Animal needs approaching, and searching the grass if a snake is signalled. Other troop members are much simpler than ours; it may be that evolution has equipped them with as much pick up the call and repeat it. Consider features 2, 4, 5, 7, 10, 13, 15 and 17. capacity for communication as they require and no more. Neurologists have pointed o Bird communication takes the form of simple calls and more elaborate songs. out that language comes at a large cost in terms of brain connections dedicated to Calls are used when flocking, nesting or warning of danger; they occasionally communication. signal aggression. Songs resemble language in that single meaningless notes are combined to form complex patterns. However, they appear to serve only two main purposes: to mark out territory and to attract a mate. They are used almost exclus­ ively by males, though they sometimes give rise to turn-taking duets, where ,two birds try to outsing each other. In some species of bird, the song is almost entirely innate; in others, it is acquired through exposure to adult song, and in others, it is partly innate and partly learnt. Consider features 2, 5, 7, 8, 10, 1 1 , 14 and 16. o Worker bees perform a ritual dance to show their fellows where to find sources of nectar. They turn round in circles to indicate that the source is close to the hive. Alternatively, they waggle their abdomens to signal that the source is some LOCALIS I N G LANG UAGE IN THE BRAIN way away. The tempo of the waggle indicates how far the source is, as does the speed at which the dancer beats its wings. The angle of the bee's body indicates the direction of the nectar; but the bee can only provide forward directions and Over the years, commentators have taken two views of the place oflanguage in the brain: has no way of indicating 'up' and 'down'. The dance is only performed by worker bees - and appears to be innate (genetically transmitted rather than learnt). Consider a that language is restricted to a single location or a limited number of locations features 1, 2, 5, 7, 8, 10, 13, 14 and 16. b that language is widely distributed throughout the brain. o Dolphins communicate under water by means of a system of 'clicks': irregular bursts of sound lasting about a millisecond and inaudible by human beings. Besides In this section, we examine some of the evidence they have uncovered. transmitting information, the clicks seem to operate as a kind of radar: their echoes Evidence for (a) would support the idea that we possess a language faculty that is enabling dolphins to locate undersea objects extremely accurately. Consider fea­ independent of other thought processes -though evidence for (b) would not rule it out. tures 1 , 2, 4, 13, and 14. Evidence from aphasia Some conclusions Early attempts to localise language in the brain relied heavily upon evidence from individuals who had suffered damage to a particular part of the brain as result of a Much 'animal speech' is no more than mimicry. A parrot trained to speak is repeat­ an accident, a stroke or surgery. In certain cases, this had a marked effect upon their ing the form of human speech with no understanding of meaning. ability to communicate in speech or in writing. b When animals are trained to respond to language, no necessary link is established In 1863, a French surgeon, Paul Broca, described the severe language impairment between word and object. A dog might be trained to beg when it hears the word of some twenty patients. In nineteen cases, the problems with language appeared to FOOD followed by a reward. But the association would be abandoned if the rewards have resulted from a brain lesion on the left side of the head, just in front of the ear ceased or the dog was punished for begging. and slightly below the top of it (technically, the lower part of the left frontal lobe). c Some forms of animal communication show one or two of the features which Later, in 1 874, a German doctor, Carl Wernicke, demonstrated a language deficit characterise language. None shows all or even most of them. associated with damage to a different area. This one was just behind and above the d Let us suppose that animals are capable of language and only held back by left ear (the posterior part of the temporal lobe).. their cognitive limitations (limited powers of thought). Then we might expect to The two areas identified by these researchers have become known, respectively, find some animals communicating in a simplified form of language. None of the as Broca's area and Wernicke's area, and seem to be especially closely associated with examples cited remotely fits this case. the processing of language by the brain. Damage to either will often (but not always) e Though complex, language is learnt by human infants without any specific lead to a condition known as aphasia, in which patients lose some of their powers of teaching. Admittedly, successful acquisition does depend upon the infant being speech. The type of language impairment varies considerably according to which of exposed to adult forms. the two areas is damaged.  I I 54 D EV E L O P M E N T L O C A L I S I N G LA N G U A G E I N T H E B R A I N 55 Wernicke's aphasia BROCA'S AREA A: so you were at D u n kirk/ B: yes/ A: what do you remember of that/ B: [na na] not very far because they kicked us out! A: dol did you have to get a boat from the beach/ B: yes/ but then we had to come back because they were/ - [sa psa psa psa] they were sending things down/ you know/ so we came back/. we came back! and we /came u p from - / right u p / then we got out! - once/ - e r e r a g u n/ er no/. what do they call them/ the very little/ the small men/. the small - A: the small men/ B: no/ small soldi e rs/. no/ the other one/. say. not soldier/. not soldier- / B: a r e they the G u rkhas/ B: no/. no/. what's the opposite to a soldier/ A: sailor B: that's it/ Key: I n both cases, A is the therapist and B the patient. WERNICKE'S AREA End of each unit of intonation marked by / Pauses marked by. (short) and - (longer) Figure 83. 1 Broca's a rea and We rnicke's a rea Source: Bishop ( 1 997: 40) Characteristics of aphasia Different symptoms are associated with Broca's and with Wernicke's aphasia. How­ ever, it should be stressed that the symptoms vary greatly from patient to patient. [ Activity 0 1 Below are transcripts of the speech of two patients, one suffering from Broca's aphasia and one suffering from Wernicke's aphasia (Source: Crystal and Varley 1998: 167-9). Table 83. 1 A compa rison of B roca's a n d Wern icke's a p hasia 1 Can you identify the differences between them and suggest which aspects of lan­ Broca's aphasia Wernicke's aphasia guage may have been damaged? 2 When you have done so, consider: how reliable is it to use this kind of data as Effortful speech; m uch pausing Effo rtless speech - fluent, rapid evidence for language localisation? A l most n o syntax Syntactica l ly wel l-structu red, complex Few function words or affixes F u nction words, affixes Broca's aphasia Mainly concrete nouns M a ny genera l nouns (e.g. thing, person) A: they do a l l sorts of activities/. woodwork and a n d verbs (e.g. do, go) B: no/ me cook/ Comprehension often good; but may Comprehension often severely i m pa i red A: you cook! great! use positio na l and semantic cues rather B: aye/. once a week/ than fu l ly u ndersta n d i n g mea n i n g A: yeah/. that's today/ Thursday/ B: aye/. and then/ - nig ht-time/ seven o'clock swi m m i ng/ A: really/ There are a number of problems in relying too heavily upon evidence based upon brain B: y e s /. smashing/ damage. A: how do you manage one-handed/ 1 Language processing by brain-damaged patients may not provide a good model B: oh it's all right/ aye/. mate/. mate. Jack comes and a l l! but - e r/. oh dear/.Jack - of language processing by normal users. er. old/ er - seventy/. no. sixty-eig ht!. Jack! - but swim/. me. me l i ke this/ - 2 Many sufferers manifest some but not all of the symptoms listed above. swimming - er/ - I can't say it/ - but Jack/ - er - swi m m i ng on front!. er - back 3 There are patients who have suffered damage to the areas identified by Broca and A: so he can do - Wernicke, without showing signs of language impairment. This suggests that the B: aye/ but one hand location of these sensitive areas may vary somewhat from one individual to another.  56 DEVELOPMENT L E X I CA L F O R M 57 Brain imaging Evidence from brain imaging suggests that language is widely distributed throughout Research into brain and language no longer has to rely solely upon evidence of the brain. There is even evidence that different lexical sets (colours, foods, tools) may aphasia. The most recent methods make use of brain imaging techniques: these track be stored in different places. The brain seems to differentiate between two types of the electrical impulses or changes to blood flow which result from heightened brain language processing - with the central parts looking after more rapid analytic opera­ activity. One such technique is PET (positron emission tomography). tions (e.g. recognising phonemes) and other parts looking after the slower, associative operations (e.g. building meaning). How can we square this with evidence of the loss of language when there is dam­ age to Broca's or Wernicke's area? If language is widely distributed across the brain, In an ingenious experiment, researchers set subjects three tasks of increasing then it must rely upon a massive system of nerve connections to transmit and assem­ complexity and used PET to monitor the way in which blood flow changed ' ble it. It seems likely that the Broca and Wernicke areas represent major junctions for in their brains. In Step I, subjects simply listened to a rapid list of words. In these networks. So what is damaged in an aphasic patient is not a separate 'language Step 2, they repeated the words as they heard them; and in Step 3, they were store' but the ability to transmit language across vital neural links. asked to say words which were associated with those they heard. Researchers monitored the increased brain activity that occurred as the tasks became more demanding. The images below (based on Posner and Raichle 1994) indicate the areas of the brain which became newly activated at each stage. LEXICAL FORM In this section we consider precisely what information is stored in the mental lexicon. What constitutes a lexical entry? Consider the following group of words: WALK - WALKS - WALKED - WALK I N G 1. hearing a rapid 2. shadowing: repeating 3. word association: generating a verb for noun {-1&21 They could be represented in two ways in the lexicon: sequimce of words rapidly presented words (-1 ) Figure 83.2 I ncreased brain activity with i ncreased task difficulty a with an entry for each of the four words Source: Adapted from Deacon ( 1 997: 296) b by the stem WALK plus a set of rules for adding inflections to it. To find out how inflections are stored in the lexicon, we need to examine the way in [Activity 01 a What is involved in each successive task? Think in terms of: which speakers assemble inflected words. We can do this by studying the errors that speakers make. They show what can happen when the assembly process goes wrong. form vs meaning - articulation (pronouncing words) - matching sounds to words Below are some examples (Aitchison 1994: 124) of Slips of the Tongue which involve - thinking of other words - short-term memory. inflections. What do they suggest about the way in which we produce the inflected Why does the motor strip down the centre of the hemisphere become involved forms of verbs? Do they favour (a) or (b) above? in Step 2? It waits to pay. b Examine the areas of the brain which became active at each stage and compare She wash upped the dishes. them with those identified by Broca and Wernicke (Figure B3. 1). Broca thought I ' d forgot abouten that. that he had discovered where in the brain language was stored. Does the imaging I want to get a cash checked ; evidence support this view? Al l the men who fighted in it. c Think of the operation of the brain as depending upon millions of nerve connec­ tions. If language is as distributed as the images above suggest - is there any way Now consider the word HAPPY. Do we assume that we have separate lexical entries we can account for the extreme effects of damage to Broca's or to Wernicke' s area? for HAPPY - UNHAPPY - HAPPINESS - UNHAPPINESS? Or is there just a single  r 58 D EV E L O P M E N T L E X I C A L FO R M 59 entry for HAPPY? Here, the situation is rather different since we are dealing with deriva­ The same question can be posed of the phonological representation. We might tional morphology. When we form UNHAPPY from HAPPY, we effectively create a assume that many speakers of southern British English have the word ENVELOPE new unit of meaning (or lexeme) a word which might qualify for separate entry in - stored in a phonological citation form as /'Dnv l up/. But how then do they re­ a dictionary in a way that WALKED would not. cognise the word in its alternative pronunciation /'env l up/? How do they recognise Another difference is that the connection between HAPPY and UNHAPPY is not /'Dnv lo:p/, the form used by many northern British speakers? Or /'Dnvl up/ as it might fixed by a rule like the connection between WALK and WALKED. There are many be pronounced in more casual speech? It is evident that the spoken forms of words are ways of forming the opposite of an English adjective, including dis- (dishonest), in­ subject to even greater variation than the written. Even within the speech of one indi­ (insufficient) and non- ( non-alcoholic); it just happens that the appropriate prefix for vidual, the pronunciation of a word varies according to where it occurs in an utterance, HAPPY is UN-. If we assume that words like UNHAPPY are assembled rather than how rapidly the person is speaking and how much importance is placed on the word. stored, then we need some kind of record in our lexical entry, telling us that UN- is What kind of phonological representation can deal with all this variation? A the appropriate prefix to attach and DIS- is not. number of solutions are possible. Here are three. To summarise: it seems to make sense to think of inflectional morphology as being specially assembled to fit a syntactic context. But the case for derivational forms is not Solution A so clear and indeed the evidence is contradictory. There are two general possibilities. The lexical entry includes all possible phonological variations of a word: it includes all the different versions of the word ENVELOPE that have been mentioned Solution A Separate entries for all derived forms of a word (HAPPY - UNHAPPY - HAPPINESS Solution 8 - UNHAPPINESS - HAPPILY), with close links between them. The lexical entry includes a single standard form of the word. But it is under-specified. In other words, when we hear the word spoken, we do not assume that all the phono­ Solution 8 logical features will be present - just some. The principle is one of achieving the best An entry for the base form of the word (HAPPY) but not for derived forms. Separate match for the word that we hear, not a perfect match. entries for productive prefixes and suffixes. Strong links between HAPPY and UN­ and HAPPY and -NESS, but none between HAPPY and DIS- or -MENT. Solution C Those who favour this second solution suggest that a speaker assembles words such The lexical entry includes a 'core value' for the word together with a range of tolerances as UNHAPPY by first accessing the base form HAPPY and then adding on the prefix around that value. Again, we do not expect a perfect match - but we recognise that UN-. A listener processes the word UNHAPPY by disassembling it (a process known the variations we hear may deviate from the 'core value' in relatively systematic ways. as prefix-stripping) and then accessing the meanings of HAPPY and UN- individually. Consider these solutions. [ 0 Activity I [Activity 0 I Consider: 1 Which is the most demanding in terms of how much we have to store in our minds? 1 Which of these solutions is the more demanding in terms ofwhat we have to store Which is the most efficient in terms of storage? in our minds? 2 Which enables a match to be found most rapidly? 2 Which seems the simpler and more rapid process? 3 Which takes most account of the ways in which words vary? 3 Compare the two forms RECEIVE and REVISIT. Might one be a better candidate 4 Do you think that any of the three is more convincing than the others? for Solution (B) than the other? The trade-off between storage and access A phonological I orthographic representation We have examined some proposals about what a lexical entry contains. They remain Most people assume that the identification of a word is the result of a simple match­ theoretical models because we do not have enough evidence to be sure which one is ing process. We read the sequence GREEN and we match it to the stored orthographic correct. But in considering them, you have achieved an important realisation about representation GREEN in our lexicon. Or we hear the sequence /gri:n/ and we find language processing. There often appears to be a trade-offbetween the amount of detail an exact match in a stored phonological representation /gri:n/. A moment's thought that we need to store in our minds and the ease of retrieving this information. Thus, will reveal that the process cannot be this straightforward. We might encounter the a model of a simple and direct way of processing linguistic information will often involve written form of GREEN in any one of the following shapes: a heavy burden in terms of how much information has to be stored in the mind. G REEN green green eer\I green green Conversely, if we try to streamline our account of what we need to store, we may find that we have to accept a more complicated process for accessing and using the infor­ So what precise form does the orthographic representation take? mation involved.