A psychometric analysis of functional category production in English agrammatic narratives

Hierarchical models of agrammatism propose that sentence production deficits can be accounted for in terms of clausal syntactic structure [Friedmann, N., & Grodzinsky, Y. (1997). Tense and agreement in agrammatic production: Pruning the syntactic tree. Brain and Language, 56, 397-425; Hagiwara, H. (1995). The breakdown of functional categories and the economy of derivation. Brain and Language, 50, 92-116]. Such theories predict that morpho-syntactic elements associated with higher nodes in the syntactic tree (complementizers and verb inflections) will be more impaired than elements associated with lower structural positions (negation markers and aspectual verb forms). While this hypothesis has been supported by the results of several studies [Benedet, M. J., Christiansen, J. A., & Goodglass, H. (1998). A cross-linguistic study of grammatical morphology in Spanish- and English-speaking agrammatic patients. Cortex, 34, 309-336; Friedmann, N. (2001). Agrammatism and the psychological reality of the syntactic tree. Journal of Psycholinguistic Research, 30, 71-88; Friedmann, N. (2002). Question production in agrammatism: The tree pruning hypothesis. Brain and Language, 80, 160-187], it has also been challenged on several grounds [Burchert, F., Swoboda-Moll, M., & De Bleser, R. (2005a). Tense and agreement dissociations in German agrammatic speakers: Underspecification vs. hierarchy. Brain and Language, 94, 188-199; Lee, M. (2003). Dissociations among functional categories in Korean agrammatism. Brain and Language, 84, 170-188; Lee, J., Milman, L. H., & Thompson, C. K. (2005). Functional category production in agrammatic speech. Brain and Language, 95, 123-124]. In this paper the question of hierarchical structure was re-examined within the framework of Item Response Theory [IRT, Rasch, G. (1980). Probabilistic models for some intelligence and attainment tests (Expanded ed.). Chicago: University of Chicago Press]. IRT is a probabilistic model widely used in the field of psychometrics to model behavioral constructs as numeric variables. In this study we examined production of functional categories (complementizers, verb inflections, negation markers, and aspectual verb forms) in narrative samples elicited from 18 individuals diagnosed with nonfluent aphasia and 18 matched controls. Data from the aphasic participants were entered into an IRT analysis to test (1) whether production of clausal functional categories can be represented as a variable on a numeric scale; and (2) whether production patterns were consistent with hierarchical syntactic structure. Pearson r correlation coefficients were also computed to determine whether there was a relation between functional category production and other indices of language performance. Results indicate that functional category production can be modeled as a numeric variable using IRT. Furthermore, although variability was observed across individuals, consistent patterns were evident when the data were interpreted within a probabilistic framework. Although functional category production was moderately correlated with a second measure of clausal structure (clause length), it was not correlated with more distant language constructs (noun/verb ratio and WAB A.Q.). These results suggest that functional category production is related to some, but not all, measures of agrammatic language performance.     

The linguistic interpretation of aphasic syndromes: Agrammatism in Broca's aphasia,an example

One of the most striking characteristics typical of the speech of Broca's aphasics is its agrammatism — the omission of ‘function’ words and inflectional morphemes. Agrammatism is generally viewed as being symptomatic of a syntactic deficit. We argue here that such an account lacks grammatical systematicity, and that the only uniform and systematic interpretation of this deficit is in terms of phonological structure. A natural class consisting of ‘function’ words and some bound morphemes can be defined with reference to the junctural properties of sentences which characterize phonological words. It is this class of elements which tend to be omitted in agrammatic speech. The goal of this paper is not only to provide an hypothesis for the interpretation of one aphasic syndrome, but also to test and illustrate the efficacy of paying close attention to substantive universals of grammatical structure in proposing accounts of linguistic deficits.     

Functional categories in agrammatism: evidence from Greek

The aim of this study is twofold. First, to investigate the use of functional categories by two Greek agrammatic aphasics. Second, to discuss the implications of our findings for the characterization of the deficit in agrammatism. The functional categories under investigation were the following: definite and indefinite articles, personal pronouns, aspect, tense, subject-verb agreement, wh-pronouns, complementizers and the mood marker na (=to). Based on data collected through different methods, it is argued that the deficit in agrammatism cannot be described in terms of a structural account but rather by means of difficulties in the implementation of grammatical knowledge.     

Bound morpheme loss errors in normal and agrammatic speech: One mechanism or two?

Loss errors involving bound morphemes in normal and agrammatic speech are examined to determine if all errors can be due to a single processing problem. It is concluded that two problems are present. First, there is a general problem with accessing bound morphemes (or forms containing bound morphemes), leading to the production of the base form. Second, there is a syntactic problem involving agreement. In agrammatism, the first problem is differentially exacerbated. Implications for normal and agrammatic speech are examined.     

Grammatical Morphemes and Conceptual Structure in Discourse Processing

The present paper analyzes how the semantic and pragmatic functions of closed class categories, or grammatical morphemes (i.e., inflections and function words), organize discourse processing. Grammatical morphemes tend to express a small set of conceptual distinctions that organize a wide range of objects and relations, usually expressed by content or open class words (i.e., nouns and verbs), into situations anchored to a discourse context. Therefore, grammatical morphemes and content words cooperate in guiding the construction of a situation model during discourse comprehension by specifying complementary aspects of described situations. The paper reviews and extends analytical and empirical evidence for this grammatical-conceptual correspondence, and suggests that the correspondence developed in response to the cognitive demands of discourse processing. Thus the distinction between open and closed linguistic categories is interpreted in terms of a fundamental correspondence between conceptual and linguistic structure that helps organize discourse processing.     

Verb deficits in Alzheimer's disease and agrammatism: implications for lexical organization

This study examined the nature of verb deficits in 14 individuals with probable Alzheimer's Disease (PrAD) and nine with agrammatic aphasia. Production was tested, controlling both semantic and syntactic features of verbs, using noun and verb naming, sentence completion, and narrative tasks. Noun and verb comprehension and a grammaticality judgment task also were administered. Results showed that while both PrAD and agrammatic subjects showed impaired verb naming, the syntactic features of verbs (i.e., argument structure) influenced agrammatic, but not Alzheimer's disease patients' verb production ability. That is, agrammatic patients showed progressively greater difficulty with verbs associated with more arguments, as has been shown in previous studies (e.g., Kim & Thompson, 2000; Thompson, 2003; Thompson, Lange, Schneider, & Shapiro, 1997), and suggest a syntactic basis for verb production deficits in agrammatism. Conversely, the semantic complexity of verbs affected PrAD, but not agrammatic, patients' performance, suggesting "bottom-up" breakdown in their verb lexicon, paralleling that of nouns, resulting from the degradation or loss of semantic features of verbs.     

Dissociations among functional categories in Korean agrammatism

This study investigated the hypothesis that the syntactic trees formed by individuals with agrammatic aphasia cannot be constructed any higher than an impaired node as suggested by the tree-pruning hypothesis (Friedman, 1994; Friedmann & Grodzinsky, 1997) and hypothesis. It also examined their following implication that the members of a certain functional category are subject to the same degree of impairment. Two experiments were conducted to investigate a Korean agrammatic patient's use and understanding of three functional categories--Mood, Tense, and Complementizer. The results showed a dissociation among functional categories that preserves the higher node while leaving the lower node impaired both in production and comprehension. Another dissociation was found among members of the same category depending on their linear position in the clause. These results contrast with the predictions of the tree-pruning hypothesis, suggesting that the nearer to the end of the clause a functional element is located, the better it is preserved in Korean agrammatism.     

Grammatical encoding in aphasia: evidence from a "processing prosthesis"

Agrammatic aphasia is characterized by severely reduced grammatical structure in spoken and written language, often accompanied by apparent insensitivity to grammatical structure in comprehension. Does agrammatism represent loss of linguistic competence or rather performance factors such as memory or resource limitations? A considerable body of evidence supports the latter hypothesis in the domain of comprehension. Here we present the first strong evidence for the performance hypothesis in the domain of production: an augmentative communication system that markedly increases the grammatical structure of agrammatic speech while providing no linguistic information, functioning merely to reduce on-line processing demands.     

Mental representation of prepositional compounds: evidence from Italian agrammatic patients

The processing of Prepositional compounds (typical Neo-latin noun--noun modifications where a head noun is modified by a prepositional phrase, e.g., mulino a vento, windmill) was preliminarily studied with a group of six agrammatic aphasic patients, and, in more detail, with a further agrammatic patient (MB). Omission was the most frequent error type in naming, whereas in the other tasks (repetition, reading, writing, and completion) errors were mostly substitutions of the target preposition. This happened even with fully lexicalized compound forms, i.e., those forms where the linking preposition is syntactically and semantically opaque. These findings are interpreted in terms of a dual-route theory of lexical access to morphologically complex words.     

Seeing pink elephants: fourteen-month-olds' interpretations of novel nouns and adjectives.

Words from different grammatical categories (e.g., nouns and adjectives) highlight different aspects of the same objects (e.g., object categories and object properties). Two experiments examine the acquisition of this phenomenon in 14-month-olds, asking whether infants can construe the very same set of objects (e.g., four purple animals) either as members of an object category (e.g., animals) or as embodying a salient object property (e.g., four purple things) and whether naming (with either count nouns or adjectives) influences infants' construals. Results suggest (1) that infants have begun to distinguish count nouns from adjectives, (2) that infants share with mature language-users an expectation that different grammatical forms highlight different aspects, and (3) that infants recruit these expectations when extending novel words. Further, these results suggest that an expectation linking count nouns to object categories emerges early in acquisition and supports the emergence of other word-to-world mappings.     

Order Matters! Influences of Linear Order on Linguistic Category Learning

Linguistic category learning has been shown to be highly sensitive to linear order, and depending on the task, differentially sensitive to the information provided by preceding category markers (premarkers, e.g., gendered articles) or succeeding category markers (postmarkers, e.g., gendered suffixes). Given that numerous systems for marking grammatical categories exist in natural languages, it follows that a better understanding of these findings can shed light on the factors underlying this diversity. In two discriminative learning simulations and an artificial language learning experiment, we identify two factors that modulate linear order effects in linguistic category learning: category structure and the level of abstraction in a category hierarchy. Regarding category structure, we find that postmarking brings an advantage for learning category diagnostic stimulus dimensions, an effect not present when categories are non-confusable. Regarding levels of abstraction, we find that premarking of super-ordinate categories (e.g., noun class) facilitates learning of subordinate categories (e.g., nouns). We present detailed simulations using a plausible candidate mechanism for the observed effects, along with a comprehensive analysis of linear order effects within an expectation-based account of learning. Our findings indicate that linguistic category learning is differentially guided by pre- and postmarking, and that the influence of each is modulated by the specific characteristics of a given category system.     

Grammatical Encoding in Aphasia: Evidence from a “Processing Prosthesis”

Agrammatic aphasia is characterized by severely reduced grammatical structure in spoken and written language, often accompanied by apparent insensitivity to grammatical structure in comprehension. Does agrammatism represent loss of linguistic competence or rather performance factors such as memory or resource limitations? A considerable body of evidence supports the latter hypothesis in the domain of comprehension. Here we present the first strong evidence for the performance hypothesis in the domain of production: an augmentative communication system that markedly increases the grammatical structure of agrammatic speech while providing no linguistic information, functioning merely to reduce on-line processing demands. Copyright 2000 Academic Press and Unisys Corporation.     

There is an entity called agrammatic aphasia.

Agrammatism as a phenomenon of neuropsychological relevance has been recently attacked--from conceptual and empirical angles. This article examines the facts, as they emerge from three recent experimental studies that have concluded that agrammatism does not exist (Miceli et al., 1989; Martin et al., 1989, Badecker et al., in press), and draws the opposite conclusion: that agrammatism is of interest to students of language and that patients belonging in this clinical category also reveal uniform patterns of aberrant behavior that are of great linguistic and psycholinguistic relevance.     

Aphasics' selective deficits in appreciating grammatical agreements

This study attempted to dissociate in aphasic patients different aspects of grammatical capacity. Subjects were asked to evaluate sentences containing violations of agreements between pronouns and verbs. Agreements which are considered primarily structural in nature were violated (e.g., a surface object case like “them” placed in a surface subject sentential slot) while other violated agreements seemed to involve both structural and semantic information (e.g., lack of agreement between a pronoun and a verb in terms of the number of people performing the act). These violations were couched in one of three types of sentential frames which varied in terms of syntactic complexity (e.g., active declarative vs. passive syntactic voices). The results revealed that Broca's aphasics found agreement violations difficult to detect in complex syntactic frames. They were quite successful at detecting even violations of the largely structural “case” type of agreement, however, when couched in simpler syntactic frames. Fluent aphasics encountered more difficulty detecting violations of agreements involving both semantic and structural information than agreements which were primarily structural in nature, that is, regardless of the syntactic frame. These unique performance profiles suggest that Broca's aphasics may be agrammatic only with respect to certain aspects of a sentence's structure, and that fluent aphasics may also experience some selective—but different—grammatical deficits.     

The quantitative analysis of agrammatic production: procedure and data

Despite the long-standing interest in structural aspects of aphasic production, no method has emerged for the systematic analysis of aphasic speech. This paper attempts to address that need by outlining a procedure for the quantitative assessment of narrative speech which yields measures for both morphological and structural characteristics of aphasic production. In addition to complete instructions for carrying out this analysis, data for three groups of subjects are presented: agrammatic aphasics, aphasics who are similarly nonfluent but not clinically judged as agrammatic, and normal controls. While the agrammatics were distinguishable from the nonagrammatic patients on most measures, both nonfluent groups showed comparable reductions in the structural complexity of their propositional utterances. Other findings include indications from individual patient data that aspects of grammatical morphology may dissociate in agrammatism.     

Syntactic comprehension deficits in agrammatism

Eleven agrammatic and 16 fluent aphasic patients were given a comprehension task consisting of simple, active and passive reversible sentences. The purpose of the study is to reconsider the comprehension disorders in agrammatism, and particularly of passive reversible sentences, to test to what extent Grodzinsky's trace deletion hypothesis (TDH) is generalizable to other types of NP-movement, and finally to ascertain whether the pattern of impairment observed in agrammatism differs from that of fluent aphasic patients. The study confirms that trace analysis may be selectively impaired in agrammatism. However, this deficit is not the only mechanism underlying comprehension disorders and cannot be said to occur in all agrammatic patients. Comprehension disorders also involve the processing of clitic object pronouns which also underly NP-movement. Finally, the impairment found in fluent aphasic patients differs, both in type and severity, from that of agrammatic patients, thus confirming the peculiar aspects of the agrammatic comprehension deficit suggested by Grodzinsky's TDH.     

Shindigs,brunches, and rodeos: The neural basis of event words

Events (e.g., “running” or “eating”) constitute a basic type within human cognition and human language. We asked whether thinking about events, as compared to other conceptual categories, depends on partially independent neural circuits. Indirect evidence for this hypothesis comes from previous studies showing elevated posterior temporal responses to verbs, which typically label events. Neural responses to verbs could, however, be driven either by their grammatical or by their semantic properties. In the present experiment, we separated the effects of grammatical class (verb vs. noun) and semantic category (event vs. object) by measuring neural responses to event nouns (e.g., “the hurricane”). Participants rated the semantic relatedness of event nouns, as well as of two categories of object nouns—animals (e.g., “the alligator”) and plants (e.g., “the acorn”)—and three categories of verbs—manner of motion (e.g., “to roll”), emission (e.g., “to sparkle”), and perception (e.g., “to gaze”). As has previously been observed, we found larger responses to verbs than to object nouns in the left posterior middle (LMTG) and superior (LSTG) temporal gyri. Crucially, we also found that the LMTG responds more to event than to object nouns. These data suggest that part of the posterior lateral temporal response to verbs is driven by their semantic properties. By contrast, a more superior region, at the junction of the temporal and parietal cortices, responded more to verbs than to all nouns, irrespective of their semantic category. We concluded that the neural mechanisms engaged when thinking about event and object categories are partially dissociable.     

Proper and common nouns: form class judgments in Broca's aphasia

Studies of agrammatic Broca's aphasics' comprehension of sentences containing articles have demonstrated profound deficits. It has not been clear whether the impairments are due to an inability to isolate the article in the stream of speech, or to difficulty in the construction and/or interpretation of various syntactic, semantic, or pragmatic levels of representation. This paper reports three experiments on Broca's aphasics' ability to distinguish between common nouns (e.g., "a rose") and proper nouns (e.g., "Rose"). This grammatical form class decision is signaled by the presence or absence of an article, and is represented at the lexical node level of linguistic analysis. The three experiments demonstrated that Broca's aphasics point to pictures representing classes of objects when asked to point to "the X" and point to pictures representing unique individuals when asked to point to "X". Thus, they were shown to be able to use the presence or absence of an article to determine lexical category. Their performance was especially accurate in an oral language context which was highly redundant and in a written language context where patients themselves could control the rate of information flow. They were quantitatively impaired, relative to controls, in a third study, which made higher information processing demands. Moreover, in this third study nonsense syllables preceding the noun which are phonologically similar to a known article were much more likely to evoke the misclassification of its noun as common than were phonologically distinct nonsense syllables. These data indicate that Broca's aphasics indeed have some difficulty isolating the article in the stream of speech. Nevertheless, detailed analyses of aphasics' performance revealed their ability to distinguish between common nouns and proper nouns even under these demanding conditions. Taken together, the three studies show that insofar as agrammatic patients are able to keep track of the presence or absence of articles, they can make a grammatical decision at the lexical node level of linguistic analysis. We conclude, then, that agrammatic Broca's aphasics are particularly impaired in the use of articles to construct and/or interpret phrasal constituents.     

Familiarity and organization of category terms in semantic memory

In order to determine production frequencies for various category terms, 219 college students were asked to generate category terms (e.g. Automobiles, Vegetables, Relatives) during a 4-rain period. The production frequency (i.e., the number of subjects who listed a particular term) for a given category term may be considered as reflecting the familiarity or amount of usage of that category term, and, as such, should be of value to memory researchers in designing experiments. Additionally, examination of the order in which terms were produced showed that subjects "clustered" related category terms, (e.g., "Countries" and "States" were often produced successively). This clustering of category terrms is supportive of the hypothesis that categories are organized in semantic memory in some kind of higher order structure.