Cognitive neuropsychology
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Cognitive neuropsychology · Sep 2002
Sequential and parallel letter processing in letter-by-letter dyslexia.
Four experiments are reported that focus on the issue of sequential vs. parallel letter processing in letter-by-letter (LBL) dyslexia; these were conducted on patient IH. Expt. 1 showed a large linear reduction of word naming times with an increase in the number of orthographic neighbours of the target (i.e., words of the same length differing by just one letter; N size). Given the large negative linear correlation existing between word length and N size, this result raises the possibility that the large word length effect diagnostic of LBL dyslexia may be, in fact, an artefact of uncontrolled N size. ⋯ Finally, Expt. 4 showed that the facilitatory effect of N size is prevented with high letter-confusability targets. These observations suggest that LBL dyslexia rests on an impairment of letter encoding that results in an excessive level of background noise in the activation of lexical-orthographic representations when letters are processed in parallel. This prevents overt identification of the target and forces sequential letter processing in order to achieve this goal.
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Cognitive neuropsychology · Jul 2002
An attribute is worth more than a category: Testing different semantic memory organisation hy potheses in relation to the living/nonliving things dissociation.
The present paper contrasted categorical and featural hypotheses of semantic memory organisation in relation to the living/nonliving things dissociation phenomenon. In the three experiments reported, normal subjects decided if word pairs representing living, nonliving, or both (mixed pairs) shared a particular perceptual (i.e., four legs, size, and hardness) or functional attribute (i.e., dangerousness, speed, and usefulness). ⋯ Both a categorical perspective and an attribute-category connection hypothesis have more difficulties in explaining the observed data. Implications for the study of semantic memory organisation and for the explanation of living/nonliving things dissociation cases are also considered.
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Cognitive neuropsychology · Dec 2000
The "living things" impairment and the nature of semantic memory organisation: An experimental study using PI-release and semantic cues.
The present paper evaluated categorical and featural proposals of memory organisation, for explaining the living/nonliving things dissociation observed in semantic memory. The experimental study used the Release from Proactive Interference (PI-release) paradigm. ⋯ The overall pattern of PI-release emphasizes the role of functional attributes and the role of structural processing to semantic processing. Implications for the different proposals presented, including possible alternative accounts of the results, are also discussed.
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Cognitive neuropsychology · Jan 1996
The Living/Nonliving Dissociation is Not an Artifact: Giving an A Priori Implausible Hypothesis a Strong Test.
Some brain-damaged patients seem to have more difficulty retrieving information about living things than about nonliving things. Does this reflect a distinction between two different underlying brain systems specialised for knowledge of living and nonliving things, or merely a difference in the diffculty of retrieving these two kinds of knowledge from a single semantic memory system ? Two recent articles (Funnell & Sheridan, 1992; Stewart, Parkin, & Hunkin, 1992) have concluded the latter, on the basis of experiments in which various determinants of naming difficulty were matched for living and nonliving things and the previously observed dissociation was found to vanish. We argue that these null effects are due to insufficient power, and that knowledge of living things can be selectively impaired. In support of this, we use the same stimulus materials, design, and data analysis as did Funnell and Sheridan (1992), with two different subjects having the same aetiology and general behaviour in the domain of semantic memory, and show that: (1) when, like the authors of these articles, we use only a single replication of each item, no effect is found, and (2) when we use more replications of the same items, highly significant differences between.