Subject-verb agreement in Spanish and English: differences in the role of conceptual constraints.

This paper reports studies of subject-verb agreement errors with speakers of Spanish and English; we used a sentence completion task, first introduced by Bock and Miller (1991). In a series of four experiments, we assessed the role of semantic information carried by the sentential subject in the induction of subject-verb agreement errors. For Spanish speakers, a sentence preamble such as la etiqueta score las botellas (the label on the bottles), which is usually interpreted to denote several labels, induced more agreement errors than preambles that normally denote a single entity. This finding replicates previous research with Italian (Vigliocco et al., 1995). English speakers, on the other hand, were not sensitive to this semantic dimension, as was found earlier by Bock and Miller (1991). This cross-linguistic difference is discussed in the framework of a modified version of the computational model of grammatical encoding proposed by Kempen and Hoenkamp (1987). In this version of the model agreement is computed through a unification operation instead of feature-copying, allowing for an independent retrieval of agreement features from the conceptual representation for the subject and the verb. We propose that languages differ in the extent to which the selection of the verb is controlled by features on the subject and features from the conceptual representation.

Syntactically based sentence processing classes: evidence from event-related brain potentials.

Theoretical considerations and diverse empirical data from clinical, psycholinguistic, and developmental studies suggest that language comprehension processes are decomposable into separate subsystems, including distinct systems for semantic and grammatical processing. Here we report that event-related potentials (ERPs) to syntactically well-formed but semantically anomalous sentences produced a pattern of brain activity that is distinct in timing and distribution from the patterns elicited by syntactically deviant sentences, and further, that different types of syntactic deviance produced distinct ERP patterns. Forty right-handed young adults read sentences presented at 2 words/sec while ERPs were recorded from over several positions between and within the hemispheres. Half of the sentences were semantically and grammatically acceptable and were controls for the remainder, which contained sentence medial words that violated (1) semantic expectations, (2) phrase structure rules, or (3) WH-movement constraints on Specificity and (4) Subjacency. As in prior research, the semantic anomalies produced a negative potential, N400, that was bilaterally distributed and was largest over posterior regions. The phrase structure violations enhanced the N125 response over anterior regions of the left hemisphere, and elicited a negative response (300-500 msec) over temporal and parietal regions of the left hemisphere. Violations of Specificity constraints produced a slow negative potential, evident by 125 msec, that was also largest over anterior regions of the left hemisphere. Violations of Subjacency constraints elicited a broadly and symmetrically distributed positivity that onset around 200 msec. The distinct timing and distribution of these effects provide biological support for theories that distinguish between these types of grammatical rules and constraints and more generally for the proposal that semantic and grammatical processes are distinct subsystems within the language faculty.

Hemisphere differences in the recognition of closed and open class words.

The distinction between closed and open class words--of interest in the first instance because of claims about the support of structural analysis during comprehension--has its reflection in word recognition. For normal speakers, performances over these types give evidence of the operation of separate recognition devices, while for agrammatic speakers, performance indicates no such separation. A study of recognition accuracy with tachistoscopic presentation lateralized to the visual hemifields suggests some parallel between left and right hemisphere processing and the contrast of normal and agrammatic speakers: with direct input restricted to the left hemisphere, the vocabulary types show different levels of accuracy; no such differences are evident with presentations to the right.

Syntactically and semantically based computations: processing of prepositions in agrammatism.

Six Broca's and six Wernicke's aphasics were tested for their processing of prepositions in different linguistic tasks which placed increasing emphasis on the use of syntactic knowledge. Subjects performed a variety of tasks involving the production and perception of sentences containing prepositions. Agrammatics' production performance was very poor. Although their comprehension performance was superior to production when asked to complete a sentence selecting the target item out of four prepositions their comprehension performance was no longer superior to production in tasks where correct performance strongly depends upon the knowledge of sentence form. These results support the view of a general incapacity of agrammatics to use knowledge of sentence structure in production and in comprehension.

Prior context and the perception of lexically ambiguous sentences.

The perceptual complexity of lexically ambiguous and unambiguous sentences was compared in three experiments. In Experiment 1, the report of ambiguous words from rapidly presented ambiguous sentences was worse than the report of corresponding unambiguous words from unambiguous sentences. Results of Experiment 2 showed that the effect was not reduced by the presence of prior biasing context within the sentence. Experiment 3 repeated the finding with a sentence meaning classification task. It was concluded that both meanings of a lexically ambiguous sentence must be computed, even when prior context makes one meaning more plausible than the other.

The interaction of perceptual processes and ambiguous sentences.

General principles of speech perception resolve several experimental conflicts about whether listeners interpret one or all meanings of an ambiguous sentence We argue that during all ambiguous clause, both meanings are processed, but immediately after the clause over, it recoded with only one meaning retained This model resolves the apparently conflicting results of previous experimental, it also predicts that underlying structure ambiguity m incomplete clauses increases Comprehension time In complete clauses, ambiguity does not increase relative comprehension time; it mayreduce comprehension time for ambiguities whose interpretations are perceptually distinct in those tasks where either meaning is appropriate Two new experiments offer preliminary confirmation of these predictions.