Agnesa Pillon

Impaired Knowledge of Visual and Non-visual Attributes in a Patient with a Semantic Impairment for Living Entities: A Case of a True Category-specific Deficit

We report a single case study of a 22-year-old, brain-damaged patient, Jennifer, who showed a semantic deficit affecting living entities (animals and fruit and vegetables) to a greater extent than non-living ones (implements and means of transport). We first show that this category effect was reliable both across time and naming conditions and that it was not an artefact of uncontrolled stimulus factors. We then show that Jennifer had no impairment at the visual or structural processing level and that her deficit was probably located at a semantic processing level. Specific semantic deficits for living entities have usually been explained by damage to the visual semantic system. However, when Jennifers access to visual and non-visual semantics was assessed through an attribute-verification task, no evidence of an attribute-specific impairment was found: Jennifer was equally impaired in retrieving visual and non-visual attributes of living entities and she was not at all impaired in retrieving visual attributes of non-living entities. Thus, the hypothesis of damage to visual semantics cannot account for the pattern of living things impairment found in this patient. Rather, this pattern seems to require the assumption that the semantic system is organized according to the living/non-living dimension.

A case of impaired knowledge for fruit and vegetables.

In this paper, we report the case of RS, a brain-damaged patient presenting with a disproportionate conceptual impairment for fruit and vegetables in comparison to animals and artefacts. We argue that such a finer-grained category-specific deficit than the living/nonliving dichotomy provides a source of critical evidence for assessing current alternative theories of conceptual organisation in the brain. The case study was designed to evaluate distinct expectations derived from the categorical and the knowledge-specific accounts for category-specific semantic deficits. In particular, the integrity of object-colour knowledge has been assessed in order to determine whether the patients deficit for fruit and vegetables was associated with a deficit for that kind of knowledge, which has been claimed to be highly diagnostic for fruit and vegetables. The results showed that the patients pattern of performance is consistent with theories assuming a topographical category-like organisation of conceptual knowledge in the brain.

The Isolation of Numerals at the Semantic Level

In this study, we examine the case of a patient (NM) who could comprehend and produce numerals despite impairment on comprehension tasks and a high degree of anemia for other categories of words. It will be claimed that NM suffered from an impairment to the semantic system affecting all categories except numerals and the series of days and months. The case of a patient presenting with the exact reverse dissociation has been described a few years ago by Cipolotti et al. (Brain 1991; 114: 619-37). We conclude that NMs pattern of performance provides evidence that numerals constitute a relevant and perhaps a distinct category at the semantic level.

Orthographic neighborhood and concreteness effects in the lexical decision task.

The experiment reported here investigated the sensitivity of concreteness effects to orthographic neighborhood density and frequency in the visual lexical decision task. The concreteness effect was replicated with a sample of concrete and abstract words that were not matched for orthographic neighborhood features and in which concrete words turned out to have a higher neighborhood density than abstract words. No consistent effect of concreteness was found with a sample of concrete and abstract words matched for orthographic neighborhood density and frequency and having fewer neighbors and higher-frequency neighbors than the words of the first sample. Post hoc analyses of the results showed that orthographic neighborhood density was not a nuisance variable producing a spurious effect of concreteness but, instead, that the existence of higher-frequency neighbors constitutes a necessary condition for concreteness effects to appear in the lexical decision task. This finding is consistent with the hypothesis that semantic information is accessed and used to generate the responses in lexical decision when inhibition from orthographic forms delays the target word recognition.

Morpheme units in speech production: Evidence from laboratory-induced verbal slips

The present experiment sought evidence of the involvement of derivational word morphology in speech production processes. A version of the word order competition technique (Baars & Motley, 1976) was used to induce a special kind of verbal slip, namely stranding exchange errors. In these errors, word fragments belonging to two words exchange by stranding their remaining fragments. The linguistic material was selected so that it could be determined whether morphemic stranding exchanges had a higher probability of occurring than non-morphemic ones under conditions in which various phonological and structural properties of the target words were controlled. The distribution of slips obtained clearly points to the implication of word derivational morphology in speech production processes.

Verbal structure of numerals and digits handwriting: new evidence from kinematics.

Two experiments used a digitizing tablet to analyse the temporal, spatial, and kinematic characteristics of handwritten production of arabic numbers. They addressed a specific issue of the numerical domain: Does the lexical and syntactic structure of verbal numerals influence the production of arabic numerals (Experiments 1 and 2), even after enforced semantic processing in a comparison task (Experiment 2)? Subjects had to write multi-digit arabic numerals (e.g., 1200) presented in two different verbal structures: a multiplicative one (e.g., teen-hundred, douze cents (twelve hundred)) or an additive one (e.g., thousand-unit-hundred, mille deux cents (one thousand two hundred)). Results show differences in the inter-digit jumps that reflect the influence of the structure of verbal numerals, even after the semantic task. This finding is discussed with regard to different models of number transcoding (McCloskey, Caramazza, & Basili, 1985; Power & Dal Martello, 1990, 1997).

A direct processing route to translate words from the first to the second language: Evidence from a case of a bilingual aphasic

How are the lexical representations corresponding to each of the languages used by a bilingual individual related within the lexical processing system(s)? Current theories of the bilingual lexical system share the assumption that the lexico-semantic level of representation and processing is common to both languages. However, there are disagreements among models on whether and how the word form representations in the first (L1) and second language (L2) are inter-connected. According to Kirsner, Lalor, and Hird (1993), only cognate forms (e.g., the French word /tabl/ and the English word /teIbl/, both meaning ‘‘table’’) are inter-connected within the bilingual lexicon, whereas Kroll and Stewart (1994) argued that the existence of crosslanguage connections was not dependent on the words being cognates or not. Thus, the ‘‘revised hierarchical model’’ (Kroll & Stewart, 1994) assumes direct connections between each L1 and L2 corresponding word forms, although L2 to L1 connections are supposed to be stronger than L1 to L2’s. Furthermore, contrary to theories of lexical processing in monolinguals (e.g., Caramazza & Hillis, 1990), these theories do not draw any explicit distinction between input and output lexical representations and processing. Therefore, it is unclear at or between which levels are connections between word forms needed to be assumed to account for the lexical performance of bilinguals. Here, we report the case of a French/English bilingual aphasic patient whose pattern of performance in naming and translation provides evidence relevant to these issues.

The pseudoprefixation effect in visual word recognition: A true - Neither strategic nor orthographic - Morphemic effect

The question of how word morphology is coded and retrieved during visual word recognition has given rise to a large number of empirical studies. The results, however, do not enable one to decide between alternative models of morphological representation and processing. It is argued in this paper that the contrast between pseudoprefixed words and non-prefixed control words can provide an empirical basis for deciding between hypotheses of morphology representation as sublexical or lexical. This contrast has been used in the three lexical decision experiments reported here, which show that decision times for pseudoprefixed words are significantly slower than for non-prefixed control words. This pseudoprefixation effect strongly supports the hypothesis that morphology is coded and processed sublexically during word recognition. The experimental conditions employed allow both strategic and strictly orthographic explanations for the pseudoprefixation effect to be dismissed.

When does action comprehension need motor involvement? Evidence from upper limb aplasia

Motor theories of action comprehension claim that comprehending the meaning of an action performed by a conspecific relies on the perceivers own motor representation of the same action. According to this view, whether an action belongs to the motor repertoire of the perceiver should impact the ease by which this action is comprehended. We tested this prediction by assessing the ability of an individual (D.C.) born without upper limbs to comprehend actions involving hands (e.g., throwing) or other body parts (e.g., jumping). The tests used a range of different visual stimuli differing in the kind of information provided. The results showed that D.C. was as accurate and fast as control participants in comprehending natural video and photographic presentations of both manual and nonmanual actions, as well as pantomimes. However, he was selectively impaired at identifying point-light animations of manual actions. This impairment was not due to a difficulty in processing kinematic information per se. D.C. was indeed as accurate as control participants in two additional tests requiring a fine-grained analysis of an actors arm or whole-body movements. These results challenge motor theories of action comprehension by showing that the visual analysis of body shape and motion provides sufficient input for comprehending observed actions. However, when body shape information is sparsely available, motor involvement becomes critical to interpret observed actions. We suggest that, with natural human movement stimuli, motor representations contribute to action comprehension each time visual information is incomplete or ambiguous.

Is motor knowledge part and parcel of the concepts of manipulable artifacts? Clues from a case of upper limb aplasia

The sensory-motor theory of conceptual representations assumes that motor knowledge of how an artifact is manipulated is constitutive of its conceptual representation. Accordingly, if we assume that the richer the conceptual representation of an object is, the easier that object is identified, manipulable artifacts that are associated with motor knowledge should be identified more accurately and/or faster than manipulable artifacts that are not (everything else being equal). In this study, we tested this prediction by investigating the identification of manipulable artifacts in an individual, DC, who was totally deprived of hand motor experience due to upper limb aplasia. This condition prevents him from interacting with most manipulable artifacts, for which he thus has no motor knowledge at all. However, he had motor knowledge for some of them, which he routinely uses with his feet. We contrasted DCs performance in a timed picture naming task for manipulable artifacts for which he had motor knowledge versus those for which he had no motor knowledge. No detectable advantage on DCs naming performance was found for artifacts for which he had motor knowledge compared to those for which he did not. This finding suggests that motor knowledge is not part of the concepts of manipulable artifacts.