Verb processing during sentence comprehension in aphasia

This study examines verb processing during on-line sentence comprehension in aphasia. We describe two experiments that explore whether a group of Broca's aphasics, who were agrammatic in comprehension as well as speech, a group of fluent aphasics, and a group of normal controls are sensitive to the argument structure arrangements of verbs. Subjects had to perform a complex secondary task both in the immediate vicinity of the verb and also at a point well past the verb while listening to sentences for meaning. Reaction times to this secondary task show that both normal controls and agrammatic Broca's aphasic subjects activate multiple argument structure possibilities for a verb in the vicinity of the verb, yet at a point downstream from the verb such effects disappear. These data suggest that the problems agrammatic subjects show with verbs in sentence comprehension, and the general lexical access deficit also recently claimed to be part of the agrammatics' problem, may not extend to the real-time processing of verbs and their arguments. Fluent aphasic subjects, on the other hand, do not show sensitivity to the argument structure properties of verbs, suggesting that these patients may have a semantic-like sentence processing deficit.     

Lexical, morphological, and syntactic aspects of verb production in agrammatic aphasics

Agrammatic aphasics do not exhibit a normal pattern of verb production; their spontaneous speech is said to lack verbs, and the verbs that are produced lack inflection. The current article focuses on the lexical, morphological, and syntactic aspects of verbs in spontaneous speech of a group of Dutch agrammatic speakers. Dutch is a so-called verb-second language in which the finite verb in the matrix clause is in the second position and nonfinite verbs are in the final position. The analysis shows that agrammatic speakers are sensitive to this relation; they virtually never produce finite verbs in the final clause position or nonfinite verbs in the second position. Nevertheless, they produce significantly fewer finite clauses than do non-brain-damaged speakers. The diversity of the lexical verbs in spontaneous speech is also lower than in non-brain-damaged speakers, but this is due to less variation in the finite lexical verbs. Hence, it is suggested that the problems with verbs in Dutch agrammatic spontaneous speech are restricted to finite lexical verbs. In an experiment, it was evaluated whether these problems with finite lexical verbs are caused by a morphological deficit or a syntactic deficit. The data show that a syntactic deficit is more likely; Dutch agrammatic speakers produce finite verbs in the base-generated position (i.e., in the embedded clause) significantly better than finite verbs that have been moved to the second position (i.e., in the matrix clause). From these data, the authors conclude that in Dutch, a verb-second language, agrammatic aphasics demonstrate specific problems with moved finite verbs, although they are perfectly aware of the relation between verb position and verb finiteness. This syntactic problem affects not only the proportion of finite verbs but also the diversity of the verbs and, hence, communicative contents.     

Verb inflection and verb diversity in three populations: agrammatic speakers, normally developing children, and children with specific language impairment (SLI)

The present study focuses on the relation between a grammatical and a lexical-semantic aspect of verb production. The spontaneous speech of three different populations (normally developing children, agrammatic aphasics, and children with a specific language impairment) has been analyzed with respect to the proportion of finite clauses and the diversity of the produced lexical verbs. The group results show that in the three populations both the proportion of finite verbs and the variability of the lexical verbs is low. When the individual scores are considered, differences between the normally developing children and the language-impaired subjects show up. Whereas in normally developing children verb finiteness and verb variability go hand-in-hand, the reverse relationship between these variables is observed in the agrammatic aphasics and the children with a specific language impairment. Given this reverse relationship, it is probable to assume two separate disorders. We therefore suggest an impairment at the interface level where lexical information and syntactic structure are integrated during sentence production.     

Sentence processing deficits in two Cantonese aphasic patients

This paper reports the performances of two Cantonese aphasics on tasks examining their sentence processing deficits. The data on sentence comprehension show that thematically noncanonical sentences, full passives, and subject-gap sentences present greater difficulty to these patients than canonical sentences, truncated passives, and object-gap sentences, respectively. These patterns are consistent with previous observations on Chinese aphasics and are expected given the structural differences between Chinese and English. In a Cantonese grammaticality judgment test, a set of structures are identified that can elicit clear judgments from normal subjects and aphasics, contrary to the claim that grammaticality judgments in Chinese are probabilistic and fragile. Most interestingly, the patients' overall performance patterns reveal a double dissociation between sentence comprehension and judgment of sentence well-formedness, suggesting that the two tasks are supported by independent processing mechanisms.     

Familiar Verbs Are Not Always Easier Than Novel Verbs: How German Pre‐School Children Comprehend Active and Passive Sentences

Many studies show a developmental advantage for transitive sentences with familiar verbs over those with novel verbs. It might be that once familiar verbs become entrenched in particular constructions, they would be more difficult to understand (than would novel verbs) in non‐prototypical constructions. We provide support for this hypothesis investigating German children using a forced‐choice pointing paradigm with reversed agent‐patient roles. We tested active transitive verbs in study 1. The 2‐year olds were better with familiar than novel verbs, while the 2½‐year olds pointed correctly for both. In study 2, we tested passives: 2½‐year olds were significantly below chance for familiar verbs and at chance for novel verbs, supporting the hypothesis that the entrenchment of the familiar verbs in the active transitive voice was interfering with interpreting them in the passive voice construction. The 3½‐year olds were also at chance for novel verbs but above chance with familiar verbs. We interpret this as reflecting a lessening of the verb‐in‐construction entrenchment as the child develops knowledge that particular verbs can occur in a range of constructions. The 4½‐year olds were above chance for both familiar and novel verbs. We discuss our findings in terms of the relative entrenchment of lexical and syntactic information and to interference between them.     

Some syntactic determinants of sentential complexity,II : Verb structure

The effect of the lexical complexity of verbs on the processing of sentences was evaluated in two experiments. Verb complexity was indexed by the number of types of grammatical structure a verb permits (e.g., a verb may be transitive or intransitive and may permit various types of complement structures). Ss’ performances in paraphrasing sentences and in solving anagrams containing complex verbs were significantly poorer than their performances with the same sentences and anagrams containing less complex verbs.     

The noun-verb problem in Chinese aphasia.

Previous studies have shown that Broca's aphasics experience a selective difficulty with action naming inside or outside of a sentence context. Conversely, it has been suggested that Wernicke's aphasics are particularly impaired in object naming. A number of explanations have been offered to account for this double dissociation, including grammatical accounts according to which the main verb problem in agrammatic Broca's aphasics is viewed as a by-product of their syntactic and/or morphological impairment, due perhaps to the greater morphological load carried by verbs (compared with nouns). In the Chinese language, there are no verb conjugations and no declensions. Hence there is no reason to expect a relationship between morphological impairment and deficits in action naming. We examined comprehension and production of object and action names, outside of a sentence context, in a sample of Chinese-speaking Broca's and Wernicke's aphasics. There was an interaction between patient group and object/action naming, but no corresponding interaction on the comprehension task. We conclude that action-naming deficits in Broca's aphasia (and/or the corresponding sparing of action names in Wernicke's aphasia) cannot be attributed to morphological differences between nouns and verbs. We also found a sublexical variant of the noun/verb dissociation applied to the internal structure of compound words made up of a verbal and a nominal element: Broca's aphasics tended to lexicalize the verbal portion of these words more often than the nominal compound, while Wernicke's showed the opposite pattern. These sublexical effects are difficult to explain in syntactic terms nor do they fit the standard lexical view. A modified lexical account is proposed, emphasizing semantic/conceptual effects in a distributed lexicon.     

Psychological verbs and the double-dependency hypothesis

The double-dependency hypothesis (DDH, Mauner et al., 1993) holds that where two dependencies of a certain kind are present, comprehension in Broca's aphasia will be random, but that where there is only one dependency, comprehension will be intact. We tested this hypothesis by examining the performance of Broca's aphasics on sentences with psychological verbs of two different classes. One class has an argument structure in which the Experiencer role is assigned to the subject. In the other class, the Experiencer role is assigned to the object. Subject-Experiencer verbs can form verbal passives which have two relevant dependencies, whereas object-Experiencer verbs can form adjectival passives and have only one relevant dependency. Thus these sentence types make contrasting predictions relevant to the DDH. Our results clearly demonstrate that patients understand the adjectival passive psychological verbs, as predicted by the DDH. On the verbal passive psychological verbs, patients perform at chance, again consistent with DDH predictions. These results firmly buttress the DDH account. They also contradict the results of an earlier study (of verbal passive psychological verbs only), a study which we argue is plagued with problems (namely, Grodzinsky, 1995b).     

Verb-based versus class-based accounts of actionality effects in children's comprehension of passives

Several studies have shown that children perform worse on tests of passive comprehension when the verb is non-actional than when it is actional. Most existing accounts focus on the semantic characteristics of the class of non-action verbs in explaining this difference. An alternative is a "verb-based" account in which passives are initially learned verb by verb, and children hear fewer non-actional passives in their language input. An analysis of the passives heard by Adam, Eve and Sarah (Brown, 1973) found more actional than non-actional passives, consistent with the verb-based account. In a second study, children tested for passive comprehension were re-tested a week later. The verb-based account predicts that children should show a consistent pattern of responses for individual verbs on test and re-test. Such consistency was found, with some inconsistency due to improvement over the re-test. Further analyses showed no effects of affectedness in explaining children's problems with passives. Finally, we discuss whether a mixed model containing both verb-based and class-based mechanisms is required to explain the actionality effects.     

The influence of semantic and morphological complexity of verbs on sentence recall: Implications for the nature of conceptual representation and category-specific deficits

One hundred and forty normal undergraduate students participated in a Proactive Interference (PI) experiment with sentences containing verbs from four different semantic and morphological classes (lexical causatives, morphological causatives, and morphologically complex and simplex perception verbs). Past research has shown significant PI build-up effects for semantically and morphologically complex verbs in isolation (de Almeida & Mobayyen, 2004). The results of the present study show that, when embedded into sentence contexts, semantically and morphologically complex verbs do not produce significant PI build-up effects. Different verb classes, however, yield different recall patterns: sentences with semantically complex verbs (e.g., causatives) were recalled significantly better than sentences with semantically simplex verbs (e.g., perception verbs). The implications for the nature of both verb-conceptual representations and category-specific semantic deficits are discussed.     

Meanings,propositions, and verbs

The event template for a verb is a lexical representation of the type of event that the verb can denote. Manner of motion verbs have a simple template: An entity is engaged in a manner of motion activity (e.g., walk). Change of location verbs have a different template: An entity changes from one location to another (e.g., arrive). We propose, and support empirically, that these templates determine the propositional structures of sentences in which the verbs are used.     

Do verb bias effects on sentence production reflect sensitivity to comprehension or production factors?

Speakers should be motivated to produce easy-to-understand sentences, but they must successfully say sentences that are harder to produce. Four experiments assessed how verb bias influences the mention of the optional “that” in sentence-complement structures. Without the “that”, such sentences can be incorrectly interpreted as including direct objects (garden paths), and especially so after direct-object-biased verbs (compared to embedded-clause-biased verbs). But direct-object-biased verbs are rarely produced as sentence-complement structures, and so they might be harder to produce as such. Experiments 1 and 2 show that speakers mention the “that” more after direct-object-biased verbs than after embedded-clause-biased verbs. Experiment 3a shows that sentences with verbs biased toward neither direct objects nor embedded subjects were often produced with the “that”, and Experiment 3b shows that postverbal noun phrases after neither-biased verbs are interpreted as direct objects less than direct-object-biased verbs and so should cause a milder garden path. Thus, frequent “that” mention is not sensitive to the tendency of a verb to be followed by a direct object, but by how rarely the verb has been produced in the formulated structure.     

Processing correlates of lexical semantic complexity

This paper explores how verb meanings that differ in semantic complexity are processed and represented. In particular, we compare eventive verbs, which denote causally structured events, with stative verbs, which denote facts without causal structure. We predicted that the conceptually more complex eventive verbs should take longer to process than stative verbs. Two experiments, a lexical decision task and a self-paced reading study, confirmed this prediction. The findings suggest that (a) semantic complexity is reflected in processing time, (b) processing verb meanings involves activating properties of the event structure beyond participants' roles, and (c) more generally, lexical event structures, which subsume thematic roles, may mediate between syntactic knowledge and semantic interpretation.     

The role of frequency in the acquisition of English word order

Akhtar [Akhtar, N. (1999). Acquiring basic word order: Evidence for data-driven learning of syntactic structure. Journal of Child Language, 26, 339–356] taught children novel verbs in ungrammatical word orders. Her results suggested that the acquisition of canonical word order is a gradual, data-driven process. The current study adapted this methodology, using English verbs of different frequencies, to test whether children's use of word order as a grammatical marker depends upon the frequency of the lexical items being ordered. Ninety-six children in two age groups (2;9 and 3;9) heard either high frequency, medium frequency or low frequency verbs that were modeled in SOV order. Children aged 2;9 who heard low frequency verbs were significantly more likely to adopt the weird word order than those who heard higher frequency verbs. Children aged 3;9 preferred to use SVO order regardless of verb frequency. Furthermore, the younger children reverted to English word order using more arguments as verb frequency increased and used more pronouns than their older counterparts. This suggests that the ability to use English word order develops from lexically specific schemas formed around frequent, distributionally regular items (e.g. verbs, pronouns) into more abstract, productive schemas as experience of the language is accrued.     

Agrammatic Broca's aphasia is not associated with a single pattern of comprehension performance

One influential hypothesis posits that the brain regions implicated in Broca's aphasia are responsible for specific syntactic operations that are necessary for the comprehension and production of sentences (Grodzinsky, 1986, 1990, in press). The empirical basis of this hypothesis is the claim that Broca's aphasics have no difficulty understanding sentences in the active voice (and other "canonical" sentence types, such as subject relatives and clefts with negative predicates), but perform at chance level with passive voice constructions (and other "noncanonical" sentences such as object-gap relatives and object clefts). In the face of well-established results indicating that Broca's aphasics can exhibit several different performance patterns on these sentence types, Grodzinsky, Pi?ango, Zurif, and Drai (1999) argued that these conflicting results do not challenge the theory when the data are analyzed appropriately. They carried out a creative statistical analysis of the comprehension performance of published cases of Broca's aphasia and concluded that all of these cases are in agreement with the predicted pattern: chance on passives and 100% correct on actives. Here we show that the statistical reasoning adopted by Grodzinsky et al. (1999) is flawed. We also show that the comprehension performance of a substantial number of the Broca's aphasics in their own sample does not conform to the pattern required. Rather, contrary to these authors' claim, Broca's aphasia is not associated with a consistent pattern of sentence comprehension performance, but allows for a number of distinct patterns in different patients.     

Event templates in the lexical representations of verbs

Four experiments support the hypothesis that syntactically relevant information about verbs is encoded in the lexicon in semantic event templates. A verb's event template represents the participants in an event described by the verb and the relations among the participants. The experiments show that lexical decision times are longer for verbs with more complex templates than verbs with less complex templates and that, for both transitive and intransitive sentences, sentences containing verbs with more complex templates take longer to process. In contrast, sentence processing times did not depend on the probabilities with which the verbs appear in transitive versus intransitive constructions in a large corpus of naturally produced sentences.     

The crucial role of tense for verb production

The case of an aphasic patient whose spontaneous speech contains very few lexical verbs is reported. Instead of sentences with lexical verbs, the patient produces many (grammatical) copular constructions. He also substitutes lexical verbs with the copula. Although this results in ungrammatical utterances, by doing so, a resemblance of sentence structure and a degree of grammaticality of his utterances are preserved. Although the patient is more impaired in naming action than object pictures, it is unlikely that lexical retrieval difficulties are solely responsible for the paucity of lexical verbs in his speech. A series of tests revealed a profound deficit in producing tense marking inflections and in understanding their significance. We argue that the unavailability of tense features is the primary reason for the lack of lexical verbs in his speech. An alternative possibility, that the tense deficit interacts with the verb retrieval deficit, is also discussed. The patient has a complex lesion and language profile, with features associated with both Broca's and Wernicke's aphasia. However, since the study focuses on his verb and tense deficits and the grammaticality of his utterances, issues that are often discussed in relation to agrammatic Broca's aphasia, the literature that is relevant to these topics and to Broca's aphasia is reviewed, despite the different diagnostic profile of the patient.