processing bound grammatical morphemes in context:...

Lanyuage and Cognitive Processes, Vol. 2, Nos. 314, pp. 245-262 (1987) 0 1988 VNU Science Press.

Processing bound grammatical morphemes in context: The case of an aphasic patient

LORRAINE KOMISARJEVSKY TYLER and HOWARD COBB University of Cambridge, England

Received April 1987; revision accepted September 1987

Abstract-This study investigates the ability of an aphasic patient (DE) to process bound grammatical morphemes in normal sentential contexts. A word monitoring task examined the patient’s sensitivity to the contextual appropriateness of derivational and inflectional suffixes. The results show that he is differentially sensitive to derivational and inflectional morphology. He is able to process derivational suffixes normally, but cannot discriminate between contextually appropriate and inappropriate inflectional suffixes. These findings are discussed with respect to current views on the processing of morphologically complex words in context.

lNTRODUCTION

The aim of the present research was to determine whether an aphasic patient (DE), whose language deficits have been extensively studied (Patterson, 1978, 1979, 198 1; Tyler, 1985, 1987) has any difficulty in processing derived and inflected words when they occur in the context of a spoken utterance. Our question was whether, in the process of interpreting a spoken utterance, this patient can successfully access the syntactic properties of different types of bound grammatical morphemes and evaluate them for their appropriateness against the prior sentential context.

We asked this question for two reasons. First, DE clearly has problems with grammatical morphemes when he produces language. His spontaneous speech contains very few bound or free grammatical morphemes. Second, previous research with DE (Tyler, 1985, 1987) shows that he has a noticeable comprehension deficit. In particular, he has difficulty using syntactic information to develop a representation of a spoken utterance. One possible interpretation of these findings is that it is problems in processing grammatical morphemes that underly his comprehension deficit.

This kind of interpretation has been proposed many times in the literature to account for the cluster of symptoms decribed as ‘agrammatism’ (e.g., see Berndt and Caramazza, 1980; Bradley et al., 1980). There has been considerable debate about the appropriateness of this concept (Badecker and Caramazza, 1985; Caplan, 1985, 1986; Caramazza and Berndt, 1985; Goodglass and Menn, 1985). Some people argue that the category is a useful one and should not be abandoned (Caplan, 1985, 1986). They claim that the appropriate research strategy is to define the linguistic behaviours which are necessary and sufficient for the diagnosis of agrammatism and then explore possible explanations for those behaviours. Others take a more radical view, claiming that the term ‘agrammatism’ confounds different types of linguistic deficits which have different

Address correspondence to L. K. Tyler, Department of Experimental Psychology, University of Cambridge, Downing Street, Cambridge CB2 3EB, England.

246 L. K. Tyler and H. Cobb

underlying explanations, and therefore it serves no useful function (Badecker and Caramazza, 1985; Caramazza, 1986).

For the purposes of the present study, arguments about the validity of the concept of agrammatism are irrelevant. However, the research which has been conducted to investigate agrammatism is relevant. It is relevant because research on the comprehension and production of the closed class morphology has been conducted almost exclusively within the framework of the debate on the nature of agrammatism. Since this research provides the background for the present study, we need to briefly consider it here.

BACKGROUND

There are many reported cases of patients who have problems in using the closed class morphology in language production. Such patients typically produce speech which is relatively free of closed class morphemes. This is not to say that bound and free grammatical morphemes are never produced, but only that they are infrequently or erroneously produced (Miceli and Caramazza, 1987). In English, such patients rarely produce morphologically complex words and free standing grammatical morphemes (such as the, and, a) are frequently omitted. In languages such as Italian and Hebrew, where an uninflected root is a non-word in the language, such patients do produce inflected words, but they tend to be inappropriate for the context (Grodzinsky, 1984).

Similar problems have been observed in comprehension. Research examining the ability of aphasics to comprehend members of the closed class falls into two categories, depending on whether the focus is on the free standing grammatical morphemes (Zurif et al., 1972; Heilman and Scholes, 1976; Goodenough et al., 1977; Bradley et al., 1980; Swinney et al., 1980; Friederici, ‘1985; Grossman et al., 1986) or on the set of bound grammatical morphemes (e.g., Patterson, 1980; Miceli and Caramazza, 1987). This research shows that some patients take longer to monitor for a closed class word compared to a word from the open class (Swinney et al.,1980; Friederici, 1985); they can not read morphologically complex words (Patterson, 1980); and they are not sensitive to the frequency characteristics of the closed class (Bradley, 1980; but see Gordon, 1983).

The general conclusion drawn from these results is that patients exhibiting these sorts of problems can not access the syntactic functional properties of closed class morphemes. They have.. . “no knowledge of the structural roles played by grammatical morphemes and. . .they are thereby unable to use these items as markers of phrasal constituents-that is, as syntactic place holders”. (Cooper and Zurif, 1983). Moreover, because the inflectional morphology is assumed to be more relevant to the development of syntactic representations than the derivational morphology (e.g., Anderson, 1982), then on this account the inflectional morphology should be more problematical than the derivational morphology. The data certainly seems to support this view (Miceli and Caramazza, 1987).

The additional attraction of this explanation is that it is consistent with a number of current psycholinguistic theories about the structure of the language processing system. These are theories which characterise the system as consisting of a number of autonomous sub-components (e.g., Forster, 1979; Bradley et al., 1980). Members of the closed class morphology are claimed to form one such autonomous sub-system. Their

Processing bound grammatical morphemes in context 247

syntactic properties are assumed to contribute towards the development of a syntactic representation during processing. If the closed class is selectively impaired as a result of brain damage, then this constitutes additional evidence that it does indeed function as a distinct sub-component within the processing system.

However, data and explanation do not converge as neatly as the foregoing might suggest. First, to determine whether a listener can exploit the syntactic properties of an element, that element has to appear in a context which allows the functional significance of those properties to have an effect. This means that the element should not appear in isolation but must appear in an appropriate context. Unfortunately, only the comprehension of free standing grammatical morphemes has been tested in this way (e.g., Goodenough et al., 1977; Grossman et al., 1986). Tests of a patient’s ability to exploit the syntactic properties of the bound grammatical morphemes has always involved presenting isolated words (e.g., Patterson, 1980; Eling, 1986) for the patient to read. This is reasonable enough when the object of the research is to study reading problems in deep dyslexics (e.g., Patterson, 1979; Coltheart, 1980). But it is surprising that no attempts have been made to study the comprehension of bound morphemes in a context where they can actually function as syntactic markers. One can not determine whether or not a patient can successfully access the syntactic properties of a morpheme, nor whether these properties are appropriately used, unless the morphemes are presented in a contextually appropriate utterance.

Second, since the processing demands of written and spoken language are different, due partly to the different temporal constraints on processing the visual and auditory input, we cannot assume that a problem in comprehending written language will be accompanied by the same problem with spoken language. In fact all of the research on the recognition of words containing bound morphemes has involved written materials, so that there are no published data on the recognition of auditorily presented polymorphemic words containing bound grammatical morphemes.

A third problem is that the inflectional and derivational morphology are rarely systematically distinguished in current research (but see Miceli and Caramazza, 1987), even though there are grounds for thinking that they should be. According to a number of linguistic theories (Aronoff, 1976; Scalise, 1984), derivations and inflections fall into relatively distinct classes. The major difference between them is in the syntactic roles which they fulfill. Inflections in English primarily have a syntactic function, marking tense, number, aspect and case. These inflectional markers (e.g., -ed, -ing) are bound up with the syntactic organization of the utterance in which they appear. The English derivational morphemes, in contrast, primarily function to change the meaning of their stems and sometimes, although not always, change the form-class of the stem. These functional differences in the two classes of morphemes have been claimed to reflect different types of lexical representation. Derived words are assumed to be fully listed in the lexicon whereas inflected words are listed in some type of decomposed form.

We might predict, therefore, that in English a derived form will be recognized in much the same way as a morphologically simple word, whereas an inflected form will be recognized by a process which decomposes the form into its stem and associated affix. There is some experimental evidence that derived forms are accessed as full forms, whereas inflected words are activated via their stems (Stanners et al., 1979; Tyler and Marsien-Wilson, 1986). This difference in the representation and processing of derived and inflected words has implications for the patterns of breakdown we might expect to

248 L. K. Tyler and H . Cob6

find after brain damage. In particular, if a patient’s deficit can be explained in terms of problems with those closed class morphemes which primarily have a syntactic function, then we would expect such a patient to have problems with the inflectional, but not with the derivational, morphology (cf. Miceli and Caramazza, 1987).

To summarize: Problems which some patients have with the comprehension of grammatical morphemes have been attributed to the functional role of grammatical morphemes in constructing a representation of an utterance. This claim has not been adequately tested. Studies typically involve presenting grammatical morphemes out of their sentential contexts, experiments are usually conducted in the written rather than the spoken modality, and there have been few attempts to distinguish the derivational and inflectional morphology.

THE EXPERIMENT

The aim of the present research was to examine whether a particular aphasic patient, DE, can access the syntactic properties of different types of bound grammatical morphemes and evaluate them for their appropriateness against the prior sentential context.

The framework for the research was the finding (Tyler and Marslen-Wilson, 1986) that normal listeners use the prior context to help in their identification of a morphologically complex word. If a word like corresponding is heard in a sentential context which makes the inflection -ing the only appropriate suffix (e.g., “Peter and Janet were old friends. For many years they had been regularly corresponding.. . ”) then listeners identify corresponding much earlier than when the word occurs in a non- constraining context where different suffixes (e.g., correspondence) are permissible (e.g., “Alice was getting worried. The only news she had received was through corresponding.. . ”).

We interpreted this finding in terms of the cohort model of spoken word-recognition (Marslen-Wilson and Welsh, 1978; Tyler and Wessells, 1983; Marslen-Wilson, 1987) which claims that the process of recognizing a spoken word involves the gradual reduction of a set of word-candidates defined on the basis of the initial sensory input. The set is reduced as its members fail to match the accumulating sensory input and when they are contextually inappropriate. For a word spoken in a context which constrains the form of the suffix, all its derivational and inflectional variants will initially be activated, but only those which meet contextual specifications will continue to be activated. In the case of the word corresponding this means that although other variants of the stem will be initially activated, their activation levels will rapidly decrease because only the -ing form is contextually appropriate.

The present study exploited this earlier finding in order to examine the processing of derived and inflected words in context. The materials consisted of sentences which contained a derived or inflected test word. This word was either contextually appropriate or inappropriate. Example (1) illustrates the general structure of the sentences which we used (with test word emphasized):

(I) The technique was very new. They claimed that it would soften tissue by a

Given the prior context, only certain morphological variants of the stem soft are contextually appropriate. In this particular case, the derivational forms sofen and

chemical reaction

Processing bound grummntical morphemes in context 249

sofily are permissable, whereas the form softness is not. Given the earlier Tyler and Marslen-Wilson (1986) result, we expect normal listeners to identify an appropriate form (soften) faster than an inappropriate form (softness).

To test this prediction we had subjects press a response key when they heard a particular target word.' This word always immediately followed the morphologically complex test word. In the example above, the word to be monitored for was tissue. We expected monitoring latencies to the target word to be affected by the speed with which the test word (soften or softness) was identified. When the test word is contextually appropriate (soften), then latencies to the target word should be faster than when it is inappropriate. When the suffix is inappropriate for the context, monitoring latencies will be disrupted because the listener will not be able to integrate the word with the prior context. There are no a priori reasons for expecting normal listeners to show any differential effects of the different types of suffix.

We also included a condition in which the test word consisted of a real stem and a real suffix which produced a non-word when combined (e.g., soft + -he). We included this condition in case DE showed no difference between the appropriate and inappropriate conditions. In this event, we would not be able to tell whether the task was insensitive to the experimental manipulations or whether he was unable to process a suffix. If his RT's in the non-word condition are significantly slower than in the appropriate condition, then we can be sure that the task is sensitive and that he does process the suffix.

DESCRIPTION OF THE PATIENT

Following in the tradition of those who argue for the case-study approach to the study of language disorders (Shallice, 1979; Morton and Patterson, 1980; Coltheart, 1985; Caramazza, 1986;), the data we report here are from an individual patient. Thii patient (DE) has been extensively described in the literature, both in terms of his reading deficits (Patterson, 1978, 1979) and in terms of his problems in understanding spoken language (Tyler, 1985).

DE was born in 1954. He was 33 when tested in the experiment reported here. When he was 16 he was involved in a motor-scooter accident which left him with a moderate right hemiplegia and aphasia. A CAT scan was performed in 1978 and this revealed a large left hemisphere lesion affecting the middle and posterior parts of the frontal lobe and most of the temporal lobe. There was no observable damage to the left parietal or occipital lobes or to the right hemisphere. He was formally educated until the age of 15 and was considered to be a pupil of average ability. After his accident he was employed as a store-keeper and has held that job ever since.

The BDAE (Goodglass and Kaplan, 1972) was administered in 1975 and 1983. The results were similar on both occasions with a slight improvement on most of the sub- tests at the second testing. On the BDAE his profile is that of a 'typical' agrammatic. Although his repetition of single words is excellent, he has difficulty repeating phrases and sentences. His speech output is effortful and consists primarily of short phrases (3- 4 words) with very few bound or free grammatical morphemes, as the following sample illustrates:

E: So have you had this job since you left school? DE: No no. . .right .. .er . ..like. ..paintin'. . .about about 4 months right .. .

out. ..next right.. .er...like cupboards. Whitewoods.. .right. ..about

250 L. K . Tyler and H . Cobb

two and a half days ... like ... left ... terrible and er ... Rose and sons ... er.. . sheet worker.. . very good.. . and er.. . my accident.. .

His auditory comprehension has been tested in a variety of ways. On the BDAE, a shortened form of the Token test (De Renzi and Vignolo, 1962), and a shortened form of the TROG (Bishop, 1982)' it is slightly below n ~ r m a l . ~

DE's ability to name common objects is a little worse than n ~ r m a l , ~ and his naming from description is only slightly i m ~ a i r e d . ~ His reading ability has been extensively studied by Patterson (1978, 1979, 1981) and he shows the error pattern of a deep dyslexic. In particular, he has problems reading suffixed words-whether they are presented in isolation or in context.6

On a number of tests designed to tap his ability to comprehend the speech input as it is heard (Tyler, 1985, 1987), he performed normally on various aspects of language processing. First, he was able to access words from the sensory input in the same way as normals (cf. Marslen-Wilson, 1987). We tested this in two ways-by means of a gating task (e.g., Grosjean, 1980; Tyler and Wessels, 1983, 1985; Tyler, 1984) and an auditory lexical decision task. The purpose of the gating task was to examine the process of mapping the sensory input onto lexical representations by estimating the amount of sensory input needed to contact the correct lexical entry. We found that DE required the same amount of sensory input as normals to correctly identify a word. This is consistent with the results of the auditory lexical decision experiment where we manipulated the point in a sequence at which it became a non-word. The idea here was that if the process of mapping the sensory input onto lexical representations is maximally efficient, then a listener will recognize a non-word at the point in the sequence at which it becomes a non-word (cf. Marslen-Wilson, 1984). Normal listeners do behave in this way, and so does DE.

In another study, we examined his ability to develop higher-level representations of the speech input as it was heard (Tyler, 1985). To do this, we had DE monitor for a target word heared in three types of prose contexts: Normal Prose (where both syntactic and semantic structural information are available), Anomalous Prose (which is grammatical but semantically anomalous) and Scrambled Prose (where there is neither syntactic nor semantic structural information). An example of each type of material, with target word emphasised, is given in (2).

(2a) Normal Prose: Everyone was outraged when they heard. Apparently, in the middle of the night some thieves broke into the church and stole a golden crucifix.

Everyone was exposed when they ate. Apparently, at the distance of the wind some ants pushed around the church and forced a new item.

(2b) Anomalous Prose:

(2c) Scrambled Prose: They everyone when outraged heard was. Of middle apparently the some the into the broke night in thieves church and crucifix stole a golden.

In addition to varying the type of prose context, we also manipulated the position of the target word in the sequence. By positioning the target word at different serial positions throughout each type of context, we were able to track the availability of different sources of processing information as they become available over time. Monitoring latencies for normal listeners decrease across Normal and Anomalous


Prose sequences, indicating that they are using syntactic and semantic information to develop a higher-level representation of the utterance. However, latencies in Scrambled Prose do not vary with the serial position of the target, and we argued that this was because there is no structural information available to the listener to facilitate monitoring latencies (Marslen-Wilson and Tyler, 1980). DE showed the same pattern as normal listeners for Normal and Scrambled Prose. However, where he differed from normal was in his responses to targets in Anomalous Prose. Latencies here were like latencies in Scrambled Prose-they did not get progressively faster throughout the sequence. We argued that this suggested that, in the absence of a meaningful interpretation of an utterance, DE was unable to develop a representation which spanned an entire utterance (Tyler, 1985).

But this does not mean that DE is unable to use any kind of syntactic information. First, his overall RTs were faster in Anomalous Prose than in Scrambled Prose and secondly, in a subsequent monitoring study (Tyler, 1987) we discovered that he could develop local syntactic phrases (e.g.. noun phrases, prepositional phrases, verb phrases). His monitoring latencies were severely disrupted when these types of local phrases were distorted in any way. Finally, DE relies much more heavily than normal listeners on the pragmatic plausibility of an utterance. When presented with a sequence like (3) and asked to monitor for the word guitar,

(3) The crowd was waiting eagerly. The young man buried the guitar and. . . his latencies were considerably slower than those of normal listeners, indicating that his ability to interpret the utterance had been severely affected by the pragmatic implausibility of the target word in relation to the prior context (Tyler, 1985).

Our predictions for DE in the present study were as follows. First, his overall word monitoring latencies should not be longer than normals’, given that they were essentially the same as those of the normal controls in three other word monitoring studies (Tyler, 1985, 1987). Second, if his comprehension deficit is partly due to his inability to access the syntactic and semantic properties of a bound morpheme and evaluate them for their contextual suitability, then he will not be able to differentiate the appropriate and inappropriate suffixes in terms of their contextual suitability. This will mean that his latencies to the two types of suffix will not differ. Third, if he has particular problems with those closed class morphemes which primarily have a syntactic function, then he should have more difficulty in processing inflectional morphemes than derivational morphemes. This will mean that RTs to inappropriate derivational suffixes will be slower than to appropriate derivational suffixes, while there should be a smaller difference in RTs to the two types of inflectional suffixes. Finally, his RTs should be slowest in the non-word condition if monitoring for a target word is sensitive to the properties of the preceding word.

METHOD

Subjects Apart from DE, we tested 6control subjects whose mean age was 37 years (range: 34-41 years)

Materials The test materials consisted of a set of 45 sentence-pairs, each containing a target word which the subject had to monitor for. Each target word was preceded by a test word.

252 L. K. Tyler and H . Cobb

The test words were always morphologically complex word-forms consisting of a base and a suffix. There were two sets of test words-those taking derivational suffixes and those taking inflectional suffixes. The base forms were chosen so that, depending on the suffix, the resulting word-form would be either: (a) appropriate for the prior context; (b) inappropriate for the prior context; or (c) a non-word (e.g., mixly, washness) formed by using the derivational suffixes used in the Appropriate and Inappropriate conditions. The frequency of the Appropriate and Inappropriate test words were matched as closely as possible. The median frequency of the sets of Appropriate and Inappropriate inflections were 14 and 11, respectively, and the median frequency of the Appropriate and Inappropriate derivations were 11 and 6, respectively (Francis and Kucera, 1982).

The test-target combinations always occurred in the second sentence of each sentence-pair. An example of a derivational set and an inflectional set, illustrating the three experimental conditions, with target word emphasized is:

Derivation

Context: Sarah could not understand why John used so much butter.

Continuation: Appropriate: He was the most wasteful cook she had ever met. Inappropriate: He was the most wastage cook she had ever met. Non-word: He was the most wastely cook she had ever met.

Inflection

Context: I have to be careful when eating ice cream.

Continuation: Appropriate: It often causes pain in my loose filling. Inappropriate: It often causing pain in my loose filling. None-word: It often causely pain in my loose filling.

The choice of suffixes was constrained by several factors. First, the target words had to be either nouns or adjectives since patients usually have no difficulty in monitoring for these word classes (cf. Tyler, 1985, 1988). Since the test words had to immediately precede the target word, this limited the set of suffixed forms that could legitimately be used. Second, in order to ensure that there were no difficulties in perceiving the suffixes, they all had to be syllabic.’ Third, as far as possible we only used suffixes which could occur in all three experimental conditions (Appropriate, Inappropriate and Non-word) in order to reduce any confounding effects due to different suffixes occurring in different conditions.

In the Appropriate condition, the suffixed form was semantically and syntactically appropriate in both the preceding and the following context. The prior syntactic structure restricted the set of suffixes that could be legitimately combined with the base form to a small set.* Out of this subset, only one suffixed form (the appropriate form) was compatible with the pragmatic context.

In the Inappropriate condition, the left context up to and including the base was contextually appropriate, but the suffix made the resulting word-form inappropriate. In example (4b) above, it is only when the listener hears the suffix [-age] in the Inappropriate condition that the word-form does not tit the context. Up to that point it is no different from the Appropriate condition.


The relationship of the Inappropriate suffix to the Appropriate suffix was different for the derivational and the inflectional sets, both syntactically and semantically. In the derivational set, the form class of the inappropriately suffixed word was different to the form class of the appropriately suffixed word. Furthermore, although derivational suffixes do change meaning, we explicitly avoided those derivations which resulted in major meaning changes (e.g., helpful vs. helpless). So, the derivations that we did use had a minor effect in changing the meaning of the stem. In contrast, the inappropriately suffixed inflections were of the same form class as the appropriately suffixed inflections, and they differed minimally in meaning.

In the Non-word condition, it is only when the suffix is processed that the violation can be detected-the verb stem is perfectly appropriate in the prior context.

Target words The target words were all common nouns or adjectives, such as: potatoes, toys, quiet. Their median frequency was 41.

Pre-tests. To obtain the 45 test items described above, we ran 2 pre-tests on an initial set of 81 items. These pre-tests established that the context, up to and including the base form of the test item, was consistent with the Appropriate suffix and inconsistent with the Inappropriate suffix. On the basis of the results from the two pre- tests, 45 items were selected for the monitoring experiment. These items were subjected to a third pre-test to establish that the acoustic realisations of the suffixes in the Inappropriate and Non-word conditions were distinguishable from the suffix in the Appropriate condition.

Pre-test 1 evaluated the extent to which the Appropriate test item fitted the context. 10 subjects were presented with the written form of the sentence-pair up to the test word, with the base form of the test item printed below. For example:

Mr Wilson went to see the doctor about his back. He hurt it yesterday when he was ... PUSH

The 81 test items were interspersed with 74 filler items which were designed to obsure the regularities of the test items. Subjects were asked to continue the incomplete sequence with an appropriate word, using the base form provided. They were also asked to rate the appropriateness of their choice on a scale of 1-5, where 5 was very appropriate and 1 was very inappropriate.

(6)

Pre-test 2 measured the extent to which the Inappropriate test items did not lit into the prior context. Nine subjects (who had not participated in pre-test 1) were presented with a written version of the sentence-pair up to and including the inappropriate form of the test item. For example:

Mr Wilson went to see the doctor about his back. He hurt it yesterday when he was PUSHES.. .

Subjects were asked to judge how well the test word fitted in with the text that preceded it, using a scale of 1-10 where 10 indicated that the word fitted in with the context extremely well and 1 indicated that it fitted the context extremely badly.

(7)


Only those items which satisfied the following criteria were subsequently tested in Pre- test 3. For each item, the appropriate form of the suffix had to be rated higher than 3.5 on pre-test 1, and the inappropriate form had to be rated less than 3.0 in pre-test 2. A total of 45 items satisfied these criteria. Of these, 21 were derivationally suffixed items and 24 were inflectionally suffixed. The mean rating of the Appropriate suffxes (on a scale of 1-5) was 4.4 for the derivational set and 4.5 for the inflectional set. The mean rating for the inappropriate items was 1.6 for the derivational set (on a scale of 1-10) and 1.5 for the inflectional set.

These items were tested in Pre-test 3 to ensure that the suffixes in all three conditions (Appropriate, Inappropriate and Non-word) could be perceived as being different from each other when presented in a spoken utterance. In this pre-test, subjects listened to the sentence-pairs over headphones and, at the same time, read a written version of the sentence-pair they were listening to. The written version always contained the correctly suffixed form. As subjects listened, they marked down any differences between what they heard and what they saw.

For this pre-test, three versions of the materials were recorded each containing an equal number of items in each of the Appropriate, Inappropriate and Non-word conditions, together with 43 filler items. Fillers were pseudo-randomly dispersed amongst the test items. Six practise items preceded the test materials. The three versions were recorded by a female native speaker of English at a normal conversational rate. Six new subjects were tested on each version of the materials, ensuring that each subject heard only one form of a test item.

The results indicated that the Inappropriate and Non-word versions of all 45 test items were easily distinguishable from the Appropriate word-forms. The mean successful detection rate of the Inappropriate forms was 99.3% and of the Non-word forms was 100%.

Monitoring experiment Those recordings of the materials which were used for pre-test 3 were also used for the monitoring experiment. In addition, we placed timing pulses at the onset of the target word. These timing pulses were located on the non-speech channel of the tape and could not be heard by the listener. They served to trigger a digital timer which was stopped when the subject pressed a response button.

Each target word was printed on a card for presentation to subjects before each trial.

Procedure DE was tested in a quiet room in his home. At each session he was tested on one version of the materials. Each of the three experimental sessions was separated by one month’s interval.

At each session, DE was presented with one of the target words printed on a card and he was asked to name the word. He then listened to the materials over headphones and pressed the response key in front of him as soon as he heard the target word. Throughout each trial the target word remained in front of him so that he would have no difficulty in remembering which word he was listening for.

The same procedure was followed for the control group. The only difference was that they were tested in our laboratory in pairs.


RESULTS AND DISCUSSION

Control group data The raw data were trimmed by replacing values more than 2.5 standard deviations from the mean by the condition mean? collapsed across affix type. We performed a series of t-tests on the individual subject data."

The individual data from the 6 controls show a very consistent pattern, with the exception of only one subject. The results (presented in Table 1) show that monitoring latencies are fastest when the target is preceded by an appropriately suffixed word. When the suffixed word is contextually inappropriate, monitoring latencies to the following word are delayed as listeners try, unsuccessfully, to integrate the suffixal form into the prior context. When the suffixed form is a non-word, processing is disrupted both because the component morphemes do not fit together to form a word and because the resulting word-form is not contextually appropriate. This results in significantly delayed monitoring RTs for the following word. Table 1 also shows that although RTs in the Non-word condition were generally longer than in the Inappropriate condition, this difference was statistically significant for only half of the subjects. This suggests that the nature of the violation in the Inappropriate and Non- word conditions was of secondary importance to the fact that these suffixed forms were contextually inappropriate.

Only one of the control subjects did not conform to this general pattern. This subject was unusual in that he failed to show a significant difference between the Appropriate and Inappropriate conditions. l 1

This overall pattern of latencies held for both the derivational and inflectional items, as Table 2 shows. The control subjects were fastest in the Appropriate condition for both derivations and inflections, with both the Inappropriate and the Non-word conditions being significantly slower than the Appropriate condition, but not differing significantly from each other.

These data suggest that, for normal listeners, the relationship between the prior context and the form of a suffix is similar for both derivational and inflectional suffixes.

Table 1. Mean response times ( R r s ) for the six control subjects and DE, collapsed across allix type. Significance levels of individual t-tests on the differences between the three conditions are also shown.

Subject Appropriate Inappropriate Non-word Differences (A) (1) (N) A-I I-N A-N

Controls 1 234 2 245 3 231 4 214 5 251 6 183 Mean 228 DE 268

334 259 313 274 315 232 288 290

349 O.oooO1 n.s. 0.00001 29 1 n.s. 0.04 0.003 350 0 . m 1 0.01 o.oooo1 296 0.00001 n.s. 0 . m 1 333 0.00001 n.s. 0.00001 264 O.oooO1 n.s. o.oo00 1

314 328 0.05 0.0006 O.oooO1


Table 2. Mean RTs and results of t-tests for the control group and DE, for the separate derivation and inflection sets.

Subject Appropriate Inappropriate Non-word Diflerences (A) (1) (N) A-I I-N A-N

Derivations Controls 1 2 3 4 5 6 Mean DE

Inflections Controls 1 2 3 4 5 6 Mean DE

177 225 219 236 212 204 222 215

188 262 248 238 243 222 234 263

221 262 331 312 321 289 29 1 301

236 251 336 315 306 26 1 285 276

280 290 337 361 334 321 32 1 331

25 I 29 1 3 59 341 332 275 308 325

0.01 ns. o.Ooo1 0.003 0.015 0.0001

0.01

o.Oo0 1 n.s. o.oO01 0.0005 0.0005 0.025

ns.

0.02 n s . n.s. ns. ns . ns .

ns .

n.s. ns . ns . ns. ns. ns .

0.002

0.0001 0.025 o.oO0 1 0.0001 0.009 0.000 1

0.0005

0.0003 n s . 0.Ooo 1 o.Ooo1 o.Ooo1 0.004

0.003

The fact that Inappropriate derivational and inflectional suffixes produce different kinds of syntactic anomaly-with inappropriate derivations producing major category violations and inappropriate inflections producing subcategory violations- does not have differential effects on the listener. Processing of the speech input is disturbed to a similar extent in response to each type of inappropriate suffix. The data also show that the prior material provides as effective a context against which to evaluate the appropriateness of a derivational suffix as an inflectional suffx. The difference of 12 ms between the mean RTs of the control group for the inflectional and derivational sets in the Appropriate condition was not significant.

DE’s data DE had no difficulty in performing this task. His latencies were fast and accurate. His mean monitoring latency was 295 ms. Although this was slower than the mean of the control group (279 ms) the difference was very small (1 6 ms) and within the normal range (277-307 ms). His mean R T for the set of filler items was 286 ms, which was slightly slower than the mean of the control group (266 ms). He missed a target on three occasions only, these misses all being in response to an adjective target. l 2

Table 1 shows DE’s mean RTs for each of the three conditions, collapsed across derivational and inflectional suffixes. Just like the control group, his latencies were fastest when the test word was correctly suffixed, and increased significantly both when the suffix was inappropriate for the prior context (268 vs. 290 ms, 443) = 1.97, p < 0.05), and when the suffix produced a non-word (268 vs. 328 ms, t(43) = 5.65, p < O.OOOO1).


The difference between the Inappropriate and Non-word conditions was also significant (290vs. 328 ms, t(43) = 3.73, p < 0.001).13

t-tests were also computed on the differences between the appropriate, inappropriate and non-word conditions for the derivations and inflections separately (Table 2). For the derivations. DE was faster in the appropriate condition than both the inappropriate condition (275 vs. 307 ms, t( 19) = 2.74, p < 0.01) and the non-word condition (275 vs. 331 ms, t(19) = 4.17, p < 0.0005). There was no significant difference between the inappropriate and non-word conditions (307vs. 331 ms, t(19) = 1.7, n.s.). Furthermore, the Appropriate-Inappropriate difference (32 ms) was within the 95% confidence limits calculated on the control group data (excluding subject 2). This overall pattern ofresults, with both types of invalid suffix leading to significant delays in response time, is the same pattern as that displayed by the control group.

In the inflection set however, his performance was different to that of the control group. He was no faster in the appropriate condition than in the inappropriate condition (263 vs. 276 ms, t(23) < 1, n.s.), but he was faster in the inappropriate condition than in the non-word condition (276 vs. 325 ms, t(23) = 3.5, p < 0.002). The 13 ms difference between the Appropriate and Inappropriate conditions was not within the 95% confidence limits calculated on the control group data. This lack of a significant difference between the Appropriate and Inappropriate conditions distinguished DE's performance from that of the control group.

These data suggest that DE treats the derivational morphology in the same way as the control group, but differs from them in his response to inflectional morphology. Like the control group, he has no problem differentiating a contextually appropriate derivation from a contextually inappropriate derivation. However, the picture is different for the inflected items. Unlike the control group, who are slowed by suffixes which are either inappropriate or illegal, DE is only slowed down by an illegal stem- suffix combination. He is insensitive to the syntactic differences between the Appropriate and Inappropriate forms.

CONCLUSIONS

In this paper we have described DE's ability to process bound grammatical morphemes when they are heard in a normal sentential context. The data show that he has problems with some aspects of the closed class morphology-namely, inflectional morphemes. His processing of the speech input is not significantly disrupted when a word contains an inflection which is inappropriate for the context. This is why his RTs to targets following inappropriately inflected words are not significantly slower than those following appropriately inflected words. In contrast, just like the control subjects, he was sensitive to the distinction between a contextually appropriate and a contextually inappropriate derivational morpheme.

This result extends previous research on the closed class morphology in two ways. First, by showing that DE is differentially sensitive to derivational and inflectional morphemes when they occur in sentential contexts, as opposed to when they occur as isolated words. Second, by showing that this sensitivity is evident in the on-line interpretation of the speech input.

There are a number of possible accounts of DE's problems with the inflectional morphology. First, he may have problems accessing the lexicon. That is, he may be unable to map the sensory input onto the appropriate form-based representation of an inflected word. Alternatively, he may have access to lexical entries but not to the


semantic and syntactic properties of those entries. Finally, it is possible that DEs problem is not located in the lexicon. He may be able to activate the semantic and syntactic properties of an inflected form, but be unable to integrate them into his representation of the utterance. We will discuss each of these possibilities in turn.

It is unlikely that DE has a problem in accessing the lexicon. He performs well in auditory lexical decision tasks using morphologically complex (Patterson, pers. comm.) and simple words, and in the data reported here he is sensitive to word/nonword differences. Evidence from a gating task demonstrates that he is able to use the sensory input efficiently. His responses to word fragments show that he accurately maps the sensory input onto representations of lexical form.

If DE can successfully access the lexicon, then his problems with the inflectional morphology may be located in the lexical representations themselves. He may be unable to correctly or fully access the syntactic and semantic properties of inflected words. Any explanation in terms of lexical representations must be able to account for the dissociation in performance between the derived and the inflected forms. There must be some principled reason why any deficit is confined to the representations of inflected words. Such a specific effect is certainly plausible- there are both linguistic and psycholinguistic grounds for assuming that the derivational and inflectional morphology are represented differently. Derivationally complex words may be represented as full-forms in the lexicon whereas inflected forms are probably represented in their decomposed form of stem and associated affixes (e.g., Scalise, 1984; Coltheart, 1985; Miceli and Caramazza, 1987; but see Butterworth, 1983). In principle then, it is possible that there can be selective loss of inflectional morphology without accompanying problems with derivational morphology.

If inflected forms are represented as a stem plus associated suffixes, one possible account of DEs problem is that he only has the stems lexically represented-all information about inflectional suffixes has been lost. This is highly improbable. First, to test a claim about loss of information is almost impossible. It would require establishing that DE neuer produces or comprehends a particular inflection. The fact that he can distinguish between valid and invalid inflected forms indicates that DE has access to emphasise representations of inflected words.

A more plausible explanation is that DE has problems in accessing the syntactic and semantic properties of inflected words. If he cannot access the semantic and syntactic properties of the suffix, then he will not be able to evaluate the contextual appropriateness of well-formed inflected word-forms. In that case he should accept any morphologically valid inflection as contextually appropriate (cf. Grodzinsky, 1984). Previous work with DE indicates that he can access the semantic properties of lexical entries, but is limited in his ability to access syntactic information (Tyler, 1985). Moreover, in the present study, there is additional evidence of DEs ability to activate semantic information. His sensitivity to the contextual appropriateness of the derivational suflixes suggests that he can activate and use the semantic properties of derived forms.14 In contrast, his inability to discriminate between the two valid inflected forms is consistent with the claim that he cannot access the syntactic properties of the inflectional suffixes. On this evidence then, it is possible to claim that DEs form-based lexical representations are intact, but that he is unable to activate the syntactic properties of inflectional suffixes.

An alternative possibility is that DE can both access and activate the syntactic properties of the inflectional morphemes, but cannot utilise this information in

Processing bound grammaticat morphemes in context 259

integrating the inflected form into higher-level representations of an utterance. In addition to activating the semantic and syntactic properties of a word-form, a

listener needs to be able to generate the appropriate type of representation against which to evaluate those properties. The different functional roles of derived and inflected forms suggests that they should be sensitive to different aspects of the prior context. Since derivational suffixes carry primarily semantic information, they should be sensitive to semantic constraints in the prior context. The primarily syntactic role of inflectional suffixes means that they should be constrained by syntactic aspects of the prior contexts. Furthermore, the fact that inflected words may be represented in their decomposed form as stem plus suffix is consistent with experimental evidence attesting to the fact that the stem and suffix are sensitive to dfjfJerent aspects of the prior context. This earlier research showed that the stem was sensitive to semantic aspects of the context, and the suffix was sensitive to the syntactic aspects (Tyler and Marslen-Wilson, 1986). To be able to integrate both derivational and inflectional suffixes then, the listener must have semantically and syntactically elaborated representations. In the case of DE there is evidence that he relies heavily upon semantic/pragmatic information to interpret an utterance and does not generate syntactically rich representations (Tyler, 1985). Even if he can activate the syntactic properties ofinflected word-forms, he may not have an adequately rich representation against which to evaluate this information. What he can do is evaluate the semantic properties of derivationally suffixed words against his semantic representation of the prior context.’

At present, we cannot arbitrate between an explanation in terms of activating the syntactic properties of the inflected word-forms and one in terms of a failure to evaluate successfully activated lexical properties against an inadequate higher-level representation. Testing these alternate accounts is the focus of our future research with DE.

NOTES 1 . We used this task because we knew from prior experience that many aphasic patients can perform the

task without any difficulty. In addition, the task enables us to assess how listeners process the speech input as they hear it (cf. Marslen-Wilson and Tyler, 1980).

2. Tested in 1979 by K. Patterson, he made 6/40 errors: 2 gender, 1 negation, 3 agent-object reversal. 3. His Token test score was 10/15 correct. 4. Howard (1985) reports a confrontation naming score of 88% correct. 5 This involves subject’s responding to descriptions such as: “What is the name of a bird that flies at night

6. Patterson did not distinguish between the derivational and inflectional morphology in her studies. 7. All except one [-able] were monosyllabic. 8. The mean number of legitimate suffixes per base form was 2.6. 9. One item was dropped from the analysis because DE missed the target three times.

and hoots”.

10. The control subjects were also analysed as a group-both over subjects and items. There was a significant effect of type of sufix (min F’(2,29) = 28.2, p < O.OOOl), but there was no significant difference between the derivation and inflection sets. A set of u posteriori Newman-Keuls comparisons using the min F‘ error term indicated that the Appropriate condition (228 ms) was significantly faster ( p < 0.05) than the Inappropriate condition (288 ms), and these were significantly different from the non-word condition ( p < 0.05). Appropriate-Inappropriate difference for the inflectional set was outside the 95% confidence limits for this group.

11. A comparison with data from a second set of older control subjects showed that this subject’s Appropriate-Inappropriate difference for the inflectional set was outside the 95% confidence limits for this group.

12. This item was excluded from all analyses.

260 L. K. Tyler and H. Cobb

13. Although DEs RT’s in the Appropriate condition might appear to be slower than those of the control group, they are within the normal range.

14. Although derived forms carry primarily semantic information, we cannot rule out the possibility that DE was also sensitive to the syntactic information that they carry.

15. Furthermore, he should also be able to evaluate the semantic properties of the stem of the inflected form against this semantic representation. This claim was not tested in the present experiment, since all of the stems were contextually appropriate.

Acknowledgements We wish to thank William Marslen-Wilson and Karalyn Patterson for helpful comments on an earlier version of the manuscript. This research was supported by an MRC programme grant to L. K. Tyler and W. D. Marslen-Wilson.

REFERENCES Anderson, S. (1983). Where’s morphology? Linguistic Inquiry 13, 571-612. Aronoff, M. (1976). Word formation in generative grammar. Linguistic Inquiry Monograph 1 . MIT Press,

Cambridge, Mass. Badecker, W. and Caramazza, A. (1985). On considerations of method and theory governing the use of

clinical categories in neurolinguistics and cognitive psychology: The case against agrarnrnatism. Cognition

Berndt, R. S . and Caramazza, A. (1980). A redefinition of the syndrome of Broca’s aphasia: Implications for a

Bishop, D. (1982). TROG Test for reception of grammar. Thomas Leach (for the Medical Research Council),

Bradley, D. (1980). Lexical representation of derivational relations. In: M. Aronoff and M-L Kean (Eds),

Bradley, D., Garrett, M. and Zurif, E. (1980). Syntactic deficits in Broca’s aphasia. In: D. Caplan (Ed.),

Buttenvorth, B. (1983). Lexical representation. In: B. Butterworth (Ed.), Language Production, Vol. 2.

Caplan, D. (1985). Syntactic and semantic structures in agrammatism. In: M.-L. Kean (Ed.), Agrammatism.

Caplan, D. (1986). In defense of agrammatism. Cognition 24, 263-276. Caramazza, A. (1986). On inferring the structure of normal cognitive systems from patterns of impaired

Caramazza, A. and Berndt, R. S. (1985). A multicomponent deficit view of agrammatic Broca’s aphasia. In:

Coltheart, M. (1980). Deep dsylexia: A review of the syndrome. In: M. Coltheart, K. Patterson and J.

Coltheart, M. (1985). Cognitive neuropsychology and the study of reading. In M. I. Posner and 0. S. M.

Cooper, W. E. and Zurif, E. (1983). Aphasia: Information processing in language production and reception.

De Renzi, E. and Vignolo, L. A. (1962). The token test: A sensitive test to detect receptive disturbances in

Eling, P. (1986). Recognition of derivations in Broca’s aphasics. Brain and Language 28, 346-356. Forster, K. I. (1979). Levels of processing and the structure of the language processor. In: W. E. Cooper and

E. C. T. Walker (Eds), Sentence Processing: Psycholinguistic Studies Presented to Merrill Garrett. Lawrence Erlbaum Associates, Hillsdale, N.J.

Francis, W.N. and Kucera, H. (1982). Frequency Analysis of English Usage: Lexicon and Grammar. Houghton MiIllin, Boston.

Friederici, A. (1985). Levels of processing and vocabulary types: Evidence from comprehension in normals and agrammatics. Cognition 19, 133-166.

20,977125.

neuropsychological model of language. Appiied Psycholinguistics I, 225-278.

Abingdon, UK.

Juncture. Anma Libri, Saratoga, Ca.

Biological Studies of Mental Processes. MIT Press, Cambridge, Mass.

Academic Press, New York.

Academic Press, New York.

performance: the case for single patient studies. Brain and Cognition 5,41-66.

M.-L. Kean (Ed.), Agrammatism. Academic Press, New York.

Marshall (Eds), Deep Dsylexia. Routledge and Kegan Paul, London.

Marin (Eds), Attention and Performance X I . Lawrence Erlbaum Associates, Hillsdale, N.J.

In: B. Buttenvorth (Ed.), Language Production, Vol. 2. Academic Press, New York.

aphasia. Brain 85,665-678.

Processing bound grammatical morphemes in context 26 1

Garrett, M. (1980). Levels of processing in sentence production. In: B. Butterworth (Ed.), Language

Goodenough, C., Zurif, E. and Weintraub, S. (1977). Aphasics’ attention to grammatical morphemes.

Goodglass, H. and Kaplan, E. (1972). The Assessment of Aphasia and Related Disorders. Lea and Febiger,

Goodglass, H. and Menn, L. (1985). Is agrammatism a unitary phenomenon? In: M.-L. Kean (Ed.),

Gordon, B. (1983). Lexical access and lexical decision: Mechanisms of frequency sensitivity. Journal of Verbal

Grodzinsky, Y. (1984). The syntactic characterization of agrammatism. Cognition 16, 99-120. Grosjean, F. (1980). Spoken word recognition processes and the gating paradigm. Perception and

Psychophysics 28, 267-283. Grossman, M., Carey, S., Zurif, E. and Diller, L. (1986). Proper and common nouns: Form class judgments in

Broca’s aphasia. Brain and Language 2s. 114-125. Heilman, K. and Scholes, R. (1976). The nature of comprehension errors in Broca’s, conduction and

Wernicke’s aphasics. Cortex 12, 258-265. Howard, D. (1985). The semantic organisation of the lexicon: Evidence from aphasia. Unpublished PhD

thesis. University College, London. Marslen-Wilson, W. D. (1984). Function and process in spoken word recognition. In: H. Bouma and

Bouwhuis (Eds), Attention and Performance X : Control of Language Processes. Lawrence Erlbaum Associates, Hillsdale, N.J.

Marslen-Wilson, W. D. (1987). Functional parallelism and spoken word recognition. Cognition 25, 71-102. Marslen-Wilson, W. D. and Welsh, A. (1978). Processing interactions and lexical access during word-

recognition in continuous speech. Cognitive Psychology 10.29 -63. Marslen-Wilson, W. D. and Tyler, L. K. (1980). The temporal structure of spoken language understanding.

Cognition 8, 1-71. Miceli, G. and Caramazza, A. (1987). Dissociation of inflectional and derivational morphology. Reports of the

Cognitive Neuropsychology Laboratory 23. The John Hopkins University, Baltimore, Maryland. Morton, J. and Patterson, K. (1980). A new attempt at an interpretation, or, an attempt at a new

interpretation. In: M. Coltheart, K. Patterson and J. Marshall (Eds), Deep Dyslexia. Routledge and Kegan Paul, London.

Patterson, K. (1978). Phonemic dyslexia: Errors of meaning and the meaning of errors. Quarterly Journal of Experimental Psychology 30,587-607.

Patterson, K. (1979). What is right with “deep” dyslexic patients? Brain and Language 8. 111-129. Patterson, K. (1980). Derivational errors. In: M. Coltheart, K. Patterson and J. Marshall (Eds), Deep

Patterson, K. (1981). Neuropsychological approaches to the study of reading. The British Journal of

Scalise, S . (1984). Generative Morphoiogy. Foris Publications, Dordrecht, Netherlands. Shallice, T. (1979). Case study approach in neuropsychological research. Journal ofclinical Neuropsychology

Stanners, R., Neiser, J., Hernon, W. and Hall, R. (1979). Memory and morphologically related words. Journal

Swinney, D., Zurif, E. and Cutler, A. (1980). EfTects ofsentential stress and word class upon comprehension in

Tyler, L. K. (1984). The structure of the initial cohort: Evidence from gating. Perception and Psychophysics

Tyler, L. K. (1985). Real-time comprehension processes in agrammatism: A case study. Brain and Language

Tyler, L. K. (1987). Spoken language comprehension in aphasia: A real-time processing perspective. In: M. Coltheart, G. Sartori and R. Job (Eds), The Cognitive Neuroscience of Language. Lawrence Erlbaum Associates, New York.

Tyler, L. K. Spoken language comprehension in a fluent aphasic patient. Cognitive Neuropsychology, in press.

Tyler, L. K. and Wessels, J. (1983). Quantifying contextual informations to word-recognition processes. Perception and Psychophysics 34, 405-420.

Production, Vol. 1 . Academic Press, New York.

Language and Speech-20, 11-19.

Philadelphia.

Agrammatism. Academic Press, New York.

Learning and Verbal Behauiour 22, 146-160.

Dyslexia. Routledge and Kegan Paul, London.

Psychology 72, 151-174.

I , 183-211.

of Verbal Learning and Verbal Behauiour 18,399-412.

Broca’s aphasia. Brain and Language 10, 132-144.

36.41 1-427.

26,259-275.

262 L. K. Tyler and H. Cob6

Tyler, L. K. and Wessels, J. (1985). Is gating an on-line task? Evidence from naming latency data. Perception and Psychophysics 38,217-222.

Tyler, L. K. and Marslen-Wilson, W. D. (1986). The effects of context on the recognition of polymorphemic words. Journal of Memory and Language 25,741 -752.

Tyler, L. K., Marslen-Wilson, W. D., Rentoul, J. and Hanney. (1987). Continuous and discontinuous access in spoken word-recognition: The role of derivational prefixes. Journal of Memory and Language, in press.

Zurif, E., Caramazza, A. and Myerson, R. (1972). Grammatical judgments of agrammatic aphasics. Neuropsychologia 10,405-417.

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