Alfonso Caramazza

Domain-Specific Knowledge Systems in the Brain: The Animate-Inanimate Distinction

We claim that the animate and inanimate conceptual categories represent evolutionarily adapted domain-specific knowledge systems that are subserved by distinct neural mechanisms, thereby allowing for their selective impairment in conditions of brain damage. On this view, (some of) the category-specific deficits that have recently been reported in the cognitive neuropsychological literaturefor example, the selective damage or sparing of knowledge about animalsare truly categorical effects. Here, we articulate and defend this thesis against the dominant, reductionist theory of category-specific deficits, which holds that the categorical nature of the deficits is the result of selective damage to noncategorically organized visual or functional semantic subsystems. On the latter view, the sensory/functional dimension provides the fundamental organizing principle of the semantic system. Since, according to the latter theory, sensory and functional properties are differentially important in determining the meaning of the members of different semantic categories, selective damage to the visual or the functional semantic subsystem will result in a category-like deficit. A review of the literature and the results of a new case of category-specific deficit will show that the domain-specific knowledge framework provides a better account of category-specific deficits than the sensory/functional dichotomy theory.

How Many Levels of Processing Are There in Lexical Access

The patterns of semantic errors in speaking and writing are used to constrain claims about the structure of lexical access mechanisms in speech and written language production. It is argued that it is not necessary to postulate a modality-neutral level of lexical representation (lemma) that is intermediate between lexical-semantic representations and modality-specific lexical representations. A dual-stage access model is proposed in which the first stage involves the selection of semantically and syntactically specified, modality-specific lexical forms, and the second stage involves the selection of specific phonological (orthographic) content for the selected lexemes.

Lexical access and inflectional morphology

Abstract This study investigated the hypothesis that lexical representations are stored in morphologically decomposed form. Three lexical decision experiments in which the morphological structure of nonword stimuli was varied are reported. Systematic effects of morphological structure on reaction time and error performance were obtained. In particular, it was found that: (1) morphologically nondecomposable nonwords were easiest to process; (2) nonwords with partial morphological structure were processed with greater difficulty than this latter set of stimuli; and, (3) morphologically legal nonwords (i.e., nonwords that are exhaustively decomposable into morphemes) were processed with the greatest difficulty. Furthermore, it was found that within the class of morphologically legal nonwords performance was affected by the type of relationship that obtained between the morphemes that comprised a stimulus item. These results, which are interpreted as evidence in favor of the hypothesis that lexical representations are morphologically decomposed, are discussed in the context of the Augmented Addressed Morphology Model.

On drawing inferences about the structure of normal cognitive systems from the analysis of patterns of impaired performance: The case for single-patient studies

An analysis of the logic of valid inferences about the structure of normal cognitive processes from the study of impaired cognitive performance in brain-damaged patients is presented. The logic of inferences from group studies and single-case studies is compared. It is shown that given certain assumptions, only the single-case method allows valid inferences about the structure of cognitive systems from the analysis of impaired performance. It is also argued that although the single-case approach is not entirely problem-free, the difficulties encountered are relatively minor.

Cognitive mechanisms in number processing and calculation: Evidence from dyscalculia

This article presents a framework for the cognitive analysis of number processing and calculation. Within this framework the primary objective is the development of a model that is sufficiently detailed to serve as a basis for explaining the number-processing/calculation performance of both normal and cognitively impaired subjects. First a general model of the cognitive mechanisms for number processing and calculation is outlined. It is shown that patterns of impairments observed in brain-damaged patients support the major assumptions of the model and that the model provides a theoretically motivated framework for interpreting the deficits. A single case is then discussed in some detail, to demonstrate that through detailed analyses of impaired performance the preliminary model can be elaborated to specify not only the general architecture of the number-processing and calculation systems, but also the inner workings of specific components and the consequences of damage to these components. The article concludes with a discussion of several general issues arising from the presented arguments.

The multiple semantics hypothesis: Multiple confusions?

Abstract In this paper we discuss the issue of multiple versus unitary semantics. We argue that the notion of multiple semantics (as currently articulated) does not, in fact, represent a theory of semantic organisation but is, instead, an arbitrary conjunction of a set of independent assumptions which are either unmotivated or, if motivated, equally compatible with a unitary semantics hypothesis. Furthermore, the empirical evidence that has been cited as support for this hypothesis is equally compatible with variants of the unitary semantics hypothesis. A model of semantic processing—the Organised Unitary Content Hypothesis (O.U.C.H.)—that is able to account for reported patterns of dissociation of performance is discussed briefly.

The Cognate Facilitation Effect: Implications for Models of Lexical Access

Do nonselected lexical nodes activate their phonological information? Catalan-Spanish bilinguals were asked to name (a) pictures whose names are cognates in the 2 languages (words that are phonologically similar in the 2 languages) and (b) pictures whose names are noncognates in the 2 languages. If nonselected lexical nodes are phonologically encoded, naming latencies should be shorter for cognate words, and because the cognate status of words is only meaningful for bilingual speakers, this difference should disappear when testing monolingual speakers. The results of Experiment 1 fully supported these predictions. In Experiment 2, the difference between cognate and noncognate words was larger when naming in the nondominant language than when naming in the dominant language. The results of the 2 experiments are interpreted as providing support to cascaded activation models of lexical access.

On the Basis for the Agrammatic's Difficulty in Producing Main Verbs

Current theories of agrammatism do not provide a clear explanation for the co-occurrence of omission of grammatical markers and main verbs in this disorder. This study tested the hypothesis that the two symptom features have distinct underlying causes. Specifically, that the omission of main verbs in agrammatic speech is caused, at least in part, by a lexical (as opposed to a syntactic) deficit. Agrammatic and anomic aphasics and normal controls were given an object and action naming test. Agrammatic patients showed a marked impairment in naming actions in contrast to anomic aphasics and normal controls who named actions better than objects. The action naming impairment in agrammatic patients was interpreted as evidence for the lexical deficit hypothesis of verb omission in the speech of these patients and as a demonstration that agrammatism is a heterogeneous disorder that implicates damage to both lexical and syntactic mechanisms.

The logic of neuropsychological research and the problem of patient classification in aphasia

A critical analysis is presented of the assumptions that must be made to use the data from aphasia to constrain models of normal language processing. The implication of these assumptions for patient classification and research methodology in aphasia is considered.

WHAT ARE THE FACTS OF SEMANTIC CATEGORY-SPECIFIC DEFICITS? A CRITICAL REVIEW OF THE CLINICAL EVIDENCE

In this study we provide a critical review of the clinical evidence available to date in the field of semantic category-specific deficits. The motivation for undertaking this review is that not all the data reported in the literature are useful for adjudicating among extant theories. This project is an attempt to answer two basic questions: (1) what are the categories of category-specific deficits, and (2) is there an interaction between impairment for a type of knowledge (e.g., visual, functional, etc.) and impairment for a given category of objects (e.g., biological, artefacts, etc.). Of the 79 case studies in which the reported data are sufficiently informative with respect to the aims of our study, 61 presented a disproportionate impairment for biological categories and 18 presented a disproportionate impairment for artefacts. Less than half of the reported cases provide statistically and theoretically interpretable data. Each case is commented upon individually. The facts that emerge from our critical review are that (1) the categories of category-specific semantic deficits are animate objects, inanimate biological objects, and artefacts (the domain of biological objects fractionates into two independent semantic categories: animals, and fruit/vegetables); (2) the types of category-specific deficits are not associated with specific types of conceptual knowledge deficits. Other conclusions that emerge from our review are that the evidence in favour of the existence of cases of reliable category-specific agnosia or anomia is not very strong, and that the visual structural description system functions relatively autonomously from conceptual knowledge about object form.