Dissociation of lexical syntax and semantics: evidence from focal cortical degeneration.

The question of whether information relevant to meaning (semantics) and structure (syntax) relies on a common language processor or on separate subsystems has proved difficult to address definitively because of the confounds involved in comparing the two types of information. At the sentence level syntactic and semantic judgments make different cognitive demands, while at the single word level, the most commonly used syntactic distinction (between nouns and verbs) is confounded with a fundamental semantic difference (between objects and actions). The present study employs a different syntactic contrast (between count nouns and mass nouns), which is crossed with a semantic difference (between naturally occurring and man-made substances) applying to words within a circumscribed semantic field (foodstuffs). We show, first, that grammaticality judgments of a patient with semantic dementia are indistinguishable from those of a group of age-matched controls, and are similar regardless of the status of his semantic knowledge about the item. In a second experiment we use the triadic task in a group of age-matched controls to show that similarity judgments are influenced not only by meaning (natural vs. manmade), but also implicitly by syntactic information (count vs. mass). Using the same task in a patient with semantic dementia we show that the semantic influences on the syntactic dimension are unlikely to account for this pattern in normals. These data are discussed in relation to modular vs. nonmodular models of language processing, and in particular to the semantic-syntactic distinction.

Effects of semantic context in the naming of pictures and words.

Two experiments investigated whether lexical retrieval for speaking can be characterized as a competitive process by assessing the effects of semantic context on picture and word naming in German. In Experiment 1 we demonstrated that pictures are named slower in the context of same-category items than in the context of items from various semantic categories, replicating findings by Kroll and Stewart (Journal of Memory and Language, 33 (1994) 149). In Experiment 2 we used words instead of pictures. Participants either named the words in the context of same- or different-category items, or produced the words together with their corresponding determiner. While in the former condition words were named faster in the context of same-category items than of different-category items, the opposite pattern was obtained for the latter condition. These findings confirm the claim that the interfering effect of semantic context reflects competition in the retrieval of lexical entries in speaking.

The anatomy of meaning and syntax.

Recent brain imaging studies have provided evidence that distinct parts of the left frontal cortex are involved in processing the structure (syntax) and meaning (semantics) of a sentence, setting the stage for the development of more precise neuroanatomical models of language processing.

Syntactic accuracy in sentence production: the case of gender disagreement in Italian language-impaired and unimpaired speakers.

We report three experiments with language-impaired and unimpaired speakers of Italian, assessing: (1) whether nonsyntactic (both conceptual and morphophonological) information is used in encoding the syntactic structure of a sentence; and (2) whether the integration of syntactic and non-syntactic information can be differentially impaired in Broca's aphasics. In all the experiments, gender agreement errors between a noun, subject of the sentence, and a predicative adjective were induced by presenting participants with sentence fragments to complete. The first experiment assessed the role of conceptual information. The second experiment investigated whether agreement is disrupted by the presence of another noun with different gender in the subject noun phrase. In the last experiment, we assessed whether morphophonological cues are used. We found that both populations used nonsyntactic information (both conceptual and morphophonological). However, patients were disrupted to a greater extent than normals by the presence of a gender mismatching noun in the subject noun phrase. The results are discussed in terms of how information integration during production is achieved and how it can be disrupted in aphasia.

Can independence be observed in a dependent system? The case of tip-of-the-tongue states.

Caramazza and Miozzo (1997) found that speakers experiencing tip-of-the-tongue states are able to report phonological information independently from syntactic information. They used this finding to reject sequential models of production, in which syntactic units (lemmas) are retrieved before form units (lexemes). To see whether this conclusion is warranted, we performed two simulation experiments based on sequential architectures. Both models we simulated produced statistically uncorrelated syntax and phonology despite sequentially retrieving lemmas and lexemes. Finally, we analyzed a corpus of Spanish errors, finding syntactic constraints on phonological word substitution errors that are not easily explained without sequentiality.

Orthographic, phonological, and articulatory contributions to masked letter and word priming.

A series of experiments assessed masked priming for letters and words that are visually similar (SIM) and dissimilar (DIS) in upper- and lowercase formats. For letters, robust DIS priming was obtained in a naming task, but this priming did not extend to a variety of non-naming tasks. For words, robust DIS priming was obtained in both naming and non-naming tasks. SIM letter and word priming extended to all tasks, but the effects were generally small for letters. The restricted set of conditions for DIS letter priming suggests that this priming is mediated by phonological-articulatory processes, and the generality of DIS word priming argues that abstract orthographic codes mediate these effects. Consistent with this conclusion, priming between homophones (for both letters and words) was found in a naming task, but little word homophone priming was obtained in a lexical decision task.

Separating hierarchical relations and word order in language production: is proximity concord syntactic or linear?

In this paper we address the question whether hierarchical relations and word order can be separated in sentence production. In two experiments, we assess whether subject-verb agreement errors (such as 'The time for fun and games are over') require linear proximity of a so-called 'local' noun ('games' in the example) to the verb. In the first experiment, we found a proximity effect when participants were asked to complete sentential beginnings of the kind: 'The helicopter for the flights'. In the second experiment, we asked participants to produce a question such as 'Is the helicopter for the flights safe?'. The syntactic relation between the subject noun and the local noun is the same in the two experiments, but the linear position of the local noun is different. The distribution of agreement errors was similar in the two experiments. We argue that these data provide evidence for a stage in language production in which a syntactic structure is built prior to a stage in which words are assigned to their linear position. Agreement is computed during the first stage.

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.

Antenatal origin of neurologic damage in newborn infants. II. Multiple gestations.

Necrosis of the cerebral white matter may be identified in living infants with echoencephalography. Echoencephalographic studies were performed in 89 twins and 12 triplets at less than 36 weeks of gestation to determine the incidence and complications associated with antenatal necrosis of the cerebral white matter. Antenatal necrosis of the cerebral white matter was identified when brain atrophy or cavities in the white matter were present by day 3 of life. Fourteen infants (13.8%) were considered to have antenatal necrosis of the cerebral white matter. The incidence of antenatal necrosis of the cerebral white matter was higher in monochorionic than in dichorionic infants (30% vs 3.3%; p less than 0.001). Univariate analysis showed that antenatal necrosis of the cerebral white matter was significantly associated with polyhydramnios, intrauterine fetal death of the cotwin, hydrops, multiple placental vascular connections, and placental artery-to-artery, vein-to-vein, and artery-to-vein anastomosis. Logistic regression analysis showed that antenatal necrosis of the cerebral white matter was predicted by the presence of either artery-to-artery or vein-to-vein anastomosis and by intrauterine fetal death of a cotwin. Vein-to-vein anastomosis had the strongest association, because 89% of seven infants with vein-to-vein anastomosis demonstrated antenatal necrosis of the cerebral white matter (p = 0.003). Monochorionic multiple gestations frequently are complicated by antenatal necrosis of the cerebral white matter. Multiple vascular connections with vein-to-vein anastomosis appear as the most important associated factor for antenatal necrosis of the cerebral white matter in this population.