Multiple route plasticity.
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Adaptation, Physiological↗
Biomedical subjects
H H Kolk
Publications and source records attributed to H H Kolk.
Agrammatic production of subject-verb agreement: the effect of conceptual number.
Three experiments tested the hypothesis that the deficit underlying agrammatic sentence production difficulties can be characterized as a limitation of computational resources and that these resources are not restricted to syntactic processing. This hypothesis was tested by eliciting subject-verb agreement errors in a sentence fragment completion paradigm. Sentence fragments were complex noun phrases, containing a subject (head) noun and a modifying prepositional phrase, containing a "local" noun. We varied the number of "tokens" a singular head noun referred to. Therefore, in one condition, grammatical and conceptual number of the head noun mismatched, whereas these numbers were the same in another condition. In Experiments 1 and 2, we observed an effect of this variable (i.e., more agreement errors when conceptual number was plural and grammatical number singular) in normal controls. Broca's aphasics, on the other hand, showed no effect. Experiment 3 consisted of a sentence/picture matching test. This test showed that the lack of effect with Broca's aphasics cannot be attributed to a comprehension deficit. We argue that these results are incompatible with the notion of a limitation in resources specific for syntactic processing. Instead, we interpret this as the result of a trade-off: Broca's aphasics lack computational resources to take into account both grammatical and conceptual information in morphosyntactic processing and rely on grammatical information only.
Adult↗
Syntactic facilitation in agrammatic sentence production.
Recently, proposals have been made to relate processing difficulties in aphasic language performance to limitations in resources for grammatical processing (Carpenter et al., 1994; Hagiwara, 1995; Kolk, 1995; Martin & Romani, 1994). Such proposals may account for a defining characteristic of agrammatic sentence production: reduced syntactic complexity. Syntactic structures that require deep hierarchical processing or reversals of canonical word order make demands exceeding limited resources. In the present study, we investigate the possibility of counteracting hypothesized resource limitations by increasing the availability of relatively complex sentences (i.e., datives and passives). The phenomenon of "syntactic priming" has been observed in a number of studies with healthy adults (e.g., Bock, 1986). With respect to Broca's aphasia, we hypothesized that increased availability of a syntactic structure, due to syntactic priming, results in a lesser demand on (limited) resources for sentence production. We elicited speech from 12 Broca's aphasics and 12 control subjects in three different conditions: spontaneous speech, picture description without priming, and picture description with priming. In addition, we varied instructions, in order to determine the role of strategies. The main findings were that (a) Brocas show stronger syntactic priming effects than controls; (b) the effects are automatic rather than strategic; and (c) in conditions with priming, Brocas produce relatively complex sentences (e.g., passives). We discuss these results in relation to capacity theories.
Adult↗
The effects of task variation on the production of grammatical morphology in Broca's aphasia: a multiple case study.
Generally task variation is not taken into account in discussions about agrammatism in Broca's aphasia. Both free speech and speech under constrained conditions are classified as "agrammatic speech." In this study, we investigated the effects of task variation on the character of agrammatic speech. We employed three types of task situations, an interview and two picture description tasks, to elicit speech from 16 Dutch and 3 German Broca's aphasics. The two picture description tasks differed in the extent to which they necessitated the production of grammatical morphology. Various task-dependent changes in the character of agrammatic speech were observed. Overall, omission rates of grammatical morphemes went down and substitution rates tended to go up in picture description as compared to free conversation. Results are discussed by contrasting two explanatory concepts, task interaction and strategic variation.
Adult↗
On-line sensitivity to subject-verb agreement violations in Broca's aphasics: the role of syntactic complexity and time.
This study examined on-line sensitivity to subject-verb agreement violations in patients with Broca's aphasia and age-matched controls using a word monitoring paradigm. The agreement violations were couched in either simple or complex syntactic frames. In a first experiment, these syntactic frames were immediately followed by the noun phrase containing the target, whereas in the second experiment a 750-msec separation was introduced. The main finding of the first experiment was that patients with Broca's aphasia showed an agreement effect only for simple (i.e., conjoined) sentences but not for complex (i.e., embedded) ones, while controls showed the expected agreement effect for both. The results of the second experiment demonstrated further that the 750-msec delay in target presentation abolished the agreement effect in Broca's aphasics but not in normal controls. The findings are interpreted to suggest that Broca's suffer from a pathological limitation in parsing capacity, giving rise to a faster than normal decay of syntactic information.
Adult↗
The production of grammatical morphology in Broca's and Wernicke's aphasics: speed and accuracy factors.
A group of Broca's aphasics (BA), Wernicke's aphasics (WA) and normal controls participated in a CLOZE experiment which required the oral production of various types of free and bound morphemes. Results provided support for the hypothesis that BA and WA share the same underlying impairment in the production of grammatical morphology. The relative difficulty of the various free and bound morpheme types was the same for BA and WA. This appeared to be the case not only in an analysis of the number of errors but also in an analysis of response times. The same analyses furthermore revealed no significant differences in the absolute levels of performance of BA and WA. Finally, it was found that BA and WA show the same relative contribution of within- and across-category substitutions of free morphemes. For bound morphemes, there was a slight difference between BA and WA, in that BA exclusively produced within-category substitutions while WA also produced some across-category substitutions.
Adult↗
On the Bradley hypothesis concerning agrammatism: the nonword-interference effect.
In 1980, D. C. Bradley, M. F. Garrett, and E. B. Zurif (in D. Caplan (Ed.), Biological studies of mental processes, Cambridge, MA: MIT Press) have proposed a lexical hypothesis on agrammatism. The theoretical background of this hypothesis is described. Then two experiments are reported with normal speakers on the so-called nonword-interference effect that has been one of the two major sources of experimental evidence for this hypothesis. The first experiment replicates the original finding that the interference effect is found when the nonword starts with a content word but not when it starts with a function word. In the second experiment, it is shown that this contrast is due to an artifact of the composition of the word list. When this list contains both content and function words, rather than only content words--as in Bradley's experiments and our Experiment I--both content and function nonwords show an equally sized interference effect. The consequences for the lexical hypothesis are discussed.
Aphasia↗
Strategy and impairment in sentence understanding by Broca's and Wernicke's aphasics.
15 Broca's aphasics and 14 Wernicke's aphasics, both German and Dutch speaking patients, were presented with a sentence-picture matching task. Both syntactic and semantic distractor pictures were used. Sentences were either reversible or non-reversible, had a topicalized or a non-topicalized word order and contained either of three types of prepositions that were labelled 'syntactic' (case-marking), 'obligatory' (subcategorized) and 'lexical' (locative). Results indicated (a) a significant difference between reversible and non reversible sentences for both Broca's and Wernicke's; (b) no significant differences between these two groups in the differences scores reversible minus non-reversible; (c) an above-chance performance on reversible sentences for both groups. To explain the pattern of differences between the various types of sentences, two schemes of interpretation are presented. The first scheme assumes that both Broca's and Wernicke's have lost basic (but different) syntactic abilities and that they can understand reversible sentences by non-syntactic strategies only. The second scheme assumes that there is no such loss, but that the impairment in Broca's and Wernicke's aphasia is such that the more syntactic analysis is required, the more errors are made. Patients are assumed to approach this task by trying to limit their syntactic analysis to the beginning of the sentence.
Adult↗
Metalinguistic judgments on sentence structure in agrammatism: a matter of task misinterpretation.
Judgments of sentence structure were studied in two non-agrammatic and four agrammatic patients. The subjects were required to sort the words from a sentence on the basis of how closely related they felt the words to be in that particular sentence. A hierarchical cluster analysis was then carried out on the data. The non-agrammatic patients produced typical "agrammatic" subjective trees in which function words and adjectives were weakly related to the rest of the sentence. The agrammatic patients produced structures that were fully normal. Two conclusions are drawn. First, this metalinguistic paradigm is inadequate as an indicator of an impairment in the mental representation of constituent structure. Second, the hypothesis that agrammatic speakers do not have such a representation is seriously weakened. Implications are discussed for the methodology of aphasia research as well as for theories on the nature of agrammatism.
Adult↗
The linguistic interpretation of Broca's aphasia a reply to M.-L. Kean.
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Aphasia↗
Judgement of sentence structure in Broca's aphasia.
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Adult↗
Syntactic persistence in Dutch.
Three experiments are reported that showed effects of "structure priming," the tendency to repeat syntactic structure across successive sentences. These effects were demonstrated in a previously untested language, Dutch. All experiments studied spoken sentence production. Importantly, pre-experimental baselines were measured for all target structures in order to assess possible effects of frequency on the magnitude of priming effect. We obtained priming with dative sentences, including datives with medially placed prepositional phrases, a sentence type not tested before. In one experiment we obtained priming effects with passives, including passives with sentence-final verbs, which also have never been tested before. However, we failed to obtain priming effects with active transitives. A comparison with the baseline data suggested that priming is not related to baseline frequency. Further, the results allowed us to draw an empirical generalization: Structure priming is a relatively long-term event, lasting at least several trials. The implications of these findings are discussed.
Humans↗