Is stimulus competition an acquisition deficit or a performance deficit?

Traditionally, blocking (X-outcome, followed by XY-outcome, resulting in attenuated conditioned responding to Y, relative to XY-outcome alone) has been explained in terms of the X-outcome association’s preventing the acquisition of the Y-outcome association. This view is challenged by models that view stimulus competition as a deficit in the expression of the acquired Y-outcome association. Here, we provide evidence that blocking is a performance deficit in which the Y-outcome association, the to-be-blocked stimulus, can affect behavioral control by the blocking stimulus (i.e., attenuate responding to X). The results are discussed in terms of acquisition and performance models of stimulus competition.     

What phonological deficit?

We review a series of experiments aimed at understanding the nature of the phonological deficit in developmental dyslexia. These experiments investigate input and output phonological representations, phonological grammar, foreign speech perception and production, and unconscious speech processing and lexical access. Our results converge on the observation that the phonological representations of people with dyslexia may be intact, and that the phonological deficit surfaces only as a function of certain task requirements, notably short-term memory, conscious awareness, and time constraints. In an attempt to reformulate those task requirements more economically, we propose that individuals with dyslexia have a deficit in access to phonological representations. We discuss the explanatory power of this concept and we speculate that a similar notion might also adequately describe the nature of other associated cognitive deficits when present.     

A rule-based categorization deficit in Alzheimer's disease?

This study examined the categorization processes that Alzheimer's disease (AD) patients use during assessments of semantic memory. Rule-based categorization involves the careful, analytic processing of strict criteria to determine category membership, particularly for items from graded categories with ambiguous category membership; similarity-based categorization requires an overall comparison of a test stimulus with a prototype or remembered exemplar of the category and is relatively effective for the rapid categorization of items with unambiguous category membership. To assess these processes in AD, patients were asked to decide the category membership of test stimuli for categories with poorly defined or fuzzy boundaries (e.g., VEGETABLE) and for categories with well-defined boundaries (e.g., FEMALE) and then to judge the representativeness of the test stimulus for its chosen category. A subgroup of AD patients demonstrated a typical pattern of impaired semantic memory compared to healthy control subjects; that is, difficulty deciding the category membership of test items from fuzzy categories. Among these patients, we found no deficit in category membership decisions about items taken from well-defined categories. We also found that AD patients and healthy controls do not differ in their representativeness judgments of items within a correctly judged category. These findings are most consistent with the hypothesis that rule-based categorization difficulty limits semantic memory in AD.     

Autism: cognitive deficit or cognitive style?

Autism is a developmental disorder characterized by impaired social and communicative development, and restricted interests and activities. This article will argue that we can discover more about developmental disorders such as autism through demonstrations of task success than through examples of task failure. Even in exploring and explaining what people with autism find difficult, such as social interaction, demonstration of competence on contrasting tasks has been crucial to defining the nature of the specific deficit. Deficit accounts of autism cannot explain, however, the assets seen in this disorder; for example, savant skills in maths, music and drawing, and islets of ability in visuospatial tests and rote memory. An alternative account, reviewed here, suggests that autism is characterized by a cognitive style biased towards local rather than global information processing – termed ‘weak central coherence’. Evidence that weak coherence might also characterize the relatives of people with autism, and form part of the extended phenotype of this largely genetic disorder, is discussed. This review concludes by considering some outstanding questions concerning the specific cognitive mechanism for coherence and the neural basis of individual differences in this aspect of information processing.     

Can a temporal processing deficit account for dyslexia?

In this comment, we argue that although Farmer and Klein (1995) have provided a valuable review relating deficits in nonreading tasks and dyslexia, their basic claim that a “temporal processing deficit” is one possible cause of dyslexia is somewhat vague. We argue that “temporal processing deficit” is never clearly defined. Furthermore, we question some of their assumptions concerning an auditory temporal processing deficit related to dyslexia, and we present arguments and data that seem inconsistent with their claims regarding how a visual temporal processing deficit would manifest itself in dyslexic readers. While we agree that some dyslexics have visual problems, we conclude that problems with reading caused by the visual mechanisms that Farmer and Klein postulate are quite rare.     

Does the autistic child have a metarepresentational deficit?

This study examines the claim that autistic children lack a “theory of mind” because of an inability to metarepresent. We argue that if autistic children have a “metarepresentational” deficit in Leslie's (1987, 1988) sense of the term, then they should have difficulty not only with mental representations such as false beliefs, but also with external representations such as photographs. Autistic children's understanding of photographic representations was tested using Zaitchik's (1990) task. This task is modelled on the false belief task (Baron-Cohen, Leslie, & Frith, 1985: Wimmer & Perner, 1983) but involves “false” photographs where a photographic representation does not conform with the current state of the real world. Like Zaitchik (1990) we found that normal 3 and 4-year-olds found this task as difficult as the false belief task. In sharp contrast, however, the autistic children in our study passed the photograph task but failed the false belief task. As both tasks require the ability to decouple, this evidence challenges the view that autistic children lack “metarepresentational” ability in Leslie's sense. However, the results leave open the question of whether autistic children have a metarepresentational ability in the different sense of the term intended by Pylyshyn (1978), that is, representing the relationship between a representation and what it represents.     

Do dyslexia and stuttering share a processing deficit?

This study assessed the prevalence of childhood stuttering in adults with dyslexia (AWD) and the prevalence of dyslexia in adults who stutter (AWS). In addition, the linguistic profiles of 50 AWD, 30 AWS and 84 neurotypical adults were measured. We found that 17 out of 50 AWD (34 %) reported stuttering during childhood compared to 1 % of the neurotypical population. This was moderated by the severity of dyslexia: People with mild dyslexia showed a lower prevalence rate (15 %) of childhood stuttering than those with severe dyslexia (47 %). In addition, we observed that 50 % of the AWS (n = 30) fulfilled the diagnostic criteria of dyslexia, even though they had never been diagnosed as dyslexic. Compared to neurotypical adults, phonological working memory, awareness, and retrieval were similarly reduced in AWS and AWD. The findings supports the view that stuttering and dyslexia may share a phonological deficit.     

Abstract conceptualization in schizophrenia: a fundamental psychological deficit?

Wright (1975) has recently argued that impairment in abstract conceptualization is an important schizophrenic deficit. We contend that the data to which he refers are insufficient support for that conclusion. Although schizophrenics' performance on sorting tasks may be less efficient than that of some other groups, the significance of this finding is debatable. A differential deficit in conceptual ability has not been shown and the confounding effects of third variables have not been ruled out. In addition, the validity of sorting techniques in measuring abstraction has not been adequately established. These methodological issues have a more general applicability to the study of psychopathology. Appreciation of them and a more specific definition of "acceptable evidence" would reduce considerably the continuing state of confusion in research on psychological deficit.     

Specific language impairment: a deficit in grammar or processing?

Specific Language Impairment (SLI) is observed in children who fail to acquire age-appropriate language skills but otherwise appear to be developing normally. There are two main hypotheses about the nature of these impairments. One assumes that they reflect impairments in the child's innate knowledge of grammar. The other is that they derive from information-processing deficits that interfere with several aspects of language learning. There is considerable evidence that SLI is associated with impaired speech processing; however, the link between this deficit and the kinds of grammatical impairments observed in these children has been unclear. We suggest that the link is provided by phonology, a speech-based code that plays important roles in learning linguistic generalizations and in working memory.     

Consonant-vowel lateralization in dyslexic children: deficit or compensatory development?

Two studies with the same subjects examined dyslexic children's puzzling superiority in forced left ear (LE) dichotic recall with consonant-vowel (CV) combinations. Thirty dysphonemic dyslexics were compared to 30 age-matched and 30 younger reading-matched normal readers. The children were tested in directed attention dichotic listening and in pseudoword decoding, word recognition, reading comprehension, spelling, arithmetic, and general intelligence (IQ). Failure to replicate the LE effect in the first experiment or in free-recall trials suggests its probable origin in aberrant attention/arousal rather than in deviant verbal lateralization. Experiment two replicated the superior LE effect in comparison to both control groups but also found the dyslexics poorer at the right ear (RE). Laterality coefficients confirmed that the dyslexics were more weakly lateralized. Corrections for stimulus dominance revealed that the uncorrected scores (1) concealed the extreme difficulty of the task and (2) obscured floor effects in the LE performance of the normals. Correlations suggest cautiously that CV lateralization may be associated inversely with reading comprehension and word decoding in the dyslexics and normal readers. The results provide mild support for the hypothesis that weak attentional lateralization for CVs in dyslexia may result from the precocious development of posterior right hemisphere attentional systems in compensation for presumed posterior left hemisphere lesions. No support was found for the competing hypothesis that such weak lateralization may be a component of the dyslexics' primary, correlated, or secondary deficit symptomatology.     

Face processing in autistics: Evidence for a generalised deficit?

Several studies have recently highlighted specific impairments in face processing in autistic subjects (memory for faces, recognition of emotional expressions, identity recognition of familiar faces). The goal of the present study was to explore whether there was a generalised face processing deficit in this population. A variety of tasks examining different, and possibly dissociative, aspects of face processing was investigated. The results of autistic subjects were compared with data from (a) a group of children with Down syndrome and (b) two individually matched control groups. The study suggests that autistic subjects are impaired in the various face processing tasks, but not always to the same extent.     

Cognitive Ethology for humans: Inconvenient truth or attentional deficit?

We discuss Kingstone et al.'s target article in the light of emerging work on cognitive ethology.     

What underlies the deficit in reported recollective experience in old age?

In recognition memory, older adults report fewer occasions on which recognition is accompanied by recollection of the original encoding context. This study asks why this occurs. Two main hypotheses were tested: (1) Older adults fail to encode the items sufficiently when first they experience them. (2) Older adults have a retrieval deficit that prevents efficient reintegration of target and context. In addition, the hypothesis that frontal lobe integrity is essential for recollective experience was examined. Twenty older (mean age 70.7 years) and 20 younger (mean age 22.9 years) adults were asked to study a list of items and to verbalize the strategies they were using to remember. A further 20 older adults (mean age 70.0 years) were tested without the think-aloud protocol. Subsequently, subjects completed a battery of psychometric tests before completing a recognition test. As expected, older adults showed less recollective experience. They differed from the young in how they encoded the material, and once this difference was accounted for, no age differences in recollective experience remained. There was little evidence to support the hypothesis that frontal lobe integrity plays a role in the reduction of recollective experience with age.     

Inhibition difficulties in preterm children: Developmental delay or persistent deficit?

Among executive functions (EFs), research has highlighted specific inhibition difficulties in preterm children. The present paper reviews and classifies the studies that assessed response inhibition and interference control abilities in preterm children and adolescents aged 3 to 16 years. Most behavioral studies agree on a developmental delay at early school age in inhibition abilities and a catch-up before adolescence, with lesser response inhibition difficulties at pre-adolescence. However, persisting interference control difficulties have been reported into early adulthood. These results are discussed, along with functional magnetic resonance imaging (fMRI) findings. Finally, this paper outlines methodological issues that need to be overcome in order to define the developmental trajectory of inhibition abilities in the preterm population.     

Alexithymia in the interpersonal domain: A general deficit of empathy?

Alexithymia and empathy have been related but very little is known on shared variance between their respective affective and cognitive dimensions. We examined this question with correlations, as well as both exploratory and confirmatory analyses, and controlled for anxiety and depression. The responses of 645 young adults to self-report questionnaires of alexithymia (TAS-20), empathy (IRI), anxiety (STAI-T) and depression (BDI-13) were examined. We observed associations between the proposed cognitive components of alexithymia (externally-oriented thinking) and that of empathy (perspective taking, fantasy) as well as empathic concern, which were insensitive to anxiety or depression. In contrast, associations between the proposed affective components of alexithymia (difficulty identifying feelings, difficulty describing feelings) and empathy (personal distress) were largely due to shared covariance with anxiety. A model encompassing an affective and a cognitive (including empathic concern) latent factors emerged, even after controlling for dysphoric affects. These findings suggest specific associations between cognitive and affective components of both constructs that were dissimilarly affected by anxiety and depression. The allocation of empathic concern to the cognitive factor is also discussed.     

Retention deficit after d-amphetamine treatment: memory defect or performance change?

Retention deficits in discrete trial delayed alternation and delayed matching to sample tasks following administration of d-amphetamine have been interpreted to support the view that arousal facilitates the decay of information from shortterm memory (STM) (Kesner, 1973). But since amphetamine causes numerous changes in performance, alternative explanations of the deficit are also plausible. In an attempt to separate drug effects on memory from those on performance, the effects of d-amphetamine on spatial memory in the radial maze were studied in rats. The unusually long span of accurate working memory in this setting permits drug administration within the retention interval as well as prior to the to-be-remembered event (TBRE). In rats tested at a 5-hr retention interval d-amphetamine (2 mg/kg) disrupted retention when given 0.5 hr before or 4.5 hr after the TBRE, but the same treatment 0 or 2 hr after the TBRE or 3 hr before the TBRE was without effect. At a 5-hr retention interval 3 mg/kg d-amphetamine impaired performance if given 2 hr after the TBRE, but not when given 0 hr after the TBRE or 3 hr before the TBRE. However, when the retention interval was lengthened to 7 hr, administering 3 mg/kg d-amphetamine 2 hr after the TBRE did not disrupt performance. The effects of d-amphetamine on spatial memory are best explained in terms of the well established effects of the drug on motor activity and appetite. Similar changes in performance may account for the "memory" impairments observed after amphetamine treatment in other tasks.     

Is there an age deficit in the selection of mental sets?

Efficient selection of actions is dependent on higher-level constraints (mental sets) on lower-level selection. This paper explores the hypothesis that ageing leads to specific impairments associated with higher-level selection between mental sets. Indirect evidence for such a deficit comes from occasional findings of age differences in situations with high executive-control demands (e.g., Mayr & Kliegl, 1993) that are not easily explained in terms of other factors, such as general slowing or working memory parameters. More direct evidence comes from recent results with the so-called task-switching paradigm. Specifically, age-sensitive set-selection processes are indicated by age differences in “global selection costs” (i.e., the response-time difference between task-switching blocks and single-task blocks) which seem to be particularly large when demands in terms of “keeping competing mental sets apart” are high. Finally, data from a new variant of the task-switching paradigm (the “fade-out paradigm”) are reported which show that age differences in global costs persist substantially beyond a phase in which set-selection is actually necessary. Generally, evidence is consistent with the view that in older age, a costly set-selection mode of processing dominates over the more efficient within-set-selection mode of processing, possibly because of a problem with maintaining distinct representations of what ought to be done in the face of competing representations of what could be done in principle.