Luisa Girelli

Gender differences in visuo-spatial processing: the importance of distinguishing between passive storage and active manipulation.

The study here reported investigates the hypothesis that gender differences in visuo-spatial abilities are mainly confined to active processing tasks. Male and female participants were required to perform passive tasks involving the recall of previously memorized positions within matrices of different sizes, as well as active tasks in which they had to mentally follow a pathway in the same matrices. The results confirmed that male superiority became evident as the active processing requirements increased while only marginal gender difference was reported in passive tasks. To strengthen the specific role of the active-passive distinction in identifying gender differences, confounding factors such as type of material and use of verbal strategies were ruled out. These findings, in line with a number of studies on individual differences, high-light the importance of addressing visuo-spatial ability as a multicomponential cognitive function which entails different type of visuo-spatial processing or mechanisms (i.e., active processing and passive storage of information) rather than as a unitary concept.

Storage and retrieval of addition facts: The role of number comparison

It is proposed that arithmetical facts are organized in memory in terms of a principle that is unique to numbers—the cardinal magnitudes of the addends. This implies that sums such as 4 + 2 and 2 + 4 are represented, and searched for, in terms of the maximum and minimum addends. This in turn implies that a critical stage in solving an addition problem is deciding which addend is the larger. The COMP model of addition fact retrieval incorporates a comparison stage, as well as a retrieval stage and a pronunciation stage. Three tasks, using the same subjects, were designed to assess the contribution of these three stages to retrieving the answers to single-digit addition problems. Task 3 was the addition task, which examined whether reaction times (RTs) were explained by the model; Task 1 was a number naming task to assess the contribution of the pronunciation stage; Task 2 was a magnitude comparison task to assess the contribution, if any, of the comparison stage. A regression equation that included just expressions of these three stages was found to account for 71% of the variance. It is argued that the COMP model fits not only the adult RT data better than do alternatives, but also the evidence from development of additional skills.

Number processing and calculation--normative data from healthy adults.

Despite the high incidence of numerical deficits in neurological patients, little attention has been paid to the development of diagnostic tools. In fact, most of the published reports on acquired numerical disorders, whether single case or group studies, do not refer to standardised measures of performance providing little, if any, control data specifically collected for the examination. In this study we present data of 282 healthy controls of different age groups and educational levels in a new battery of Number Processing and Calculation (NPC). The NPC battery includes a total of 35 tasks, assessing different counting abilities, various aspects of number comprehension (such as parity and magnitude judgements), numerical transcoding, calculation, arithmetic reasoning and conceptual knowledge. Special attention is paid to the assessment of different calculation abilities, including simple fact retrieval, rule based processing, mental calculation and written calculation in all four operations. Moreover, text problem solving is assessed as well as the understanding of arithmetic principles. Thus, the NPC battery differs from the EC 301 battery proposed by Deloche et al., 1994 (Dellatolas, Deloche, Basso, & Claros-Salinas, 2001) and allows a more fine grained diagnosis which is relevant for planning targeted interventions. The battery is easy to administer and does not require special materials or equipment.

Numerical skills and aphasia

The aim of this study was to investigate numerical difficulties in 50 patients with left hemispheric lesions. Aphasic patients were grouped according to their type of aphasia diagnosed by the Aachener Aphasia Test. The overall error rate in various transcoding and calculation tasks was clearly correlated with the severity of the language deficit, global aphasics being the most impaired patients. Brocas and Wernickes aphasics scored similarly at the quantitative level, and amnesic aphasics were less impaired. Interestingly, qualitative analysis of the errors indicated that each group presented with specific difficulties, partially reflecting the nature of the language problems. In simple calculation, multiplication was found to be the most impaired operation, in particular in Brocas aphasics. This result supports the hypothesis that the retrieval of multiplication facts is preferentially mediated by verbal processing. Calculation procedures were mainly impaired in Wernickes and global aphasics.

A Deficit for Arithmetical Procedures: Lack of Knowledge or Lack of Monitoring?

A patient is described with a specific deficit for arithmetical procedures. Unlike in previously described cases, where the observed problems could be attributed to the systematic application of disturbed algorithms, this patients difficulty seems to stem from an inability to monitor the sequence of operations that calculation procedures specify. Criteria are provided for distinguishing impairments in written calculation due to the application of defective knowledge of the procedures from those determined by lack of monitoring. The role of monitoring and control processes in different calculation components is also discussed.

Subtraction Bugs in an Acalculic Patient

We report a patient, MT, who presented a specific, though not isolated, deficit in written calculation. Despite a preserved knowledge of simple arithmetic - single-digit addition and subtraction - he failed systematically in multi-digit subtraction. The nature of errors was consistent across problems and reflected the application of a disturbed underlying algorithm. Moreover, the pattern of error observed mimies a very common finding in developmental studies on arithmetical procedure acquisition (Fuson, 1990, 1992, Young and OShea, 1981; VanLehn, 1986, 1990). The data suggest that, within calculation skills, syntax may exist as a system of stable, but inappropriate, rules which are independent of any underlying conceptual knowledge.

When ‘Alfa Romeo’ facilitates 164: Semantic effects in verbal number production

Abstract In this study we investigate the effect of different notations (arabic/alphabetical) and the effect of different tasks on the verbal production of number words. ZA, an aphasic and dyslexic patient, showed a significant improvement in the reading of alphabetical stimuli (number words, words, non-words), but not of arabic stimuli over a period of 3 years. Moreover, ZAs verbal number production was significantly better in semantic tasks that involved encyclopaedic knowledge of numbers and the transcoding of quantities than in asemantic reading tasks. The verbal number production in response to calculations (both arithmetic facts and complex calculations), on the other hand, did not differ from the performance in reading tasks. The results of this study are consistent with the assumption of semantic and asemantic routes in number transcoding.

Strategic learning in the rehabilitation of semantic knowledge

The aim of the present study was to evaluate the efficacy of a reorganisation approach in the rehabilitation of simple arithmetic deficits as an instance of disturbed semantic knowledge. We report the case of FS, who underwent targeted training to overcome specific difficulties with multiplication facts. The programme was based on the strategic use of his residual knowledge and explicit reference to the principles underlying simple arithmetic. The purpose of this approach was to facilitate the reacquisition process by reducing the number of facts to be memorised and inducing a meaningful organisation of this knowledge in memory. The positive outcome of the intervention speaks in favour of a reorganisation rationale in the rehabilitation of arithmetic skills, where the integration of declarative, procedural, and conceptual knowledge critically mediate the re-acquisition process.

Numerical abilities in dementia

The purpose of the present paper is to provide a critical review of the neuropsychological evidence elucidating the incidence and nature of numerical difficulties in dementia. Though long neglected, the occurrence of dyscalculia in the early stage of Alzheimers disease (AD) has caught the attention of many, and both group studies and single-case investigations converge in identifying number processing and numerical difficulties among the early signs of dementia. Yet analysis of the available data suggests that the pattern of decline may vary greatly across individuals: numerical difficulties may be highly selective and limited to single processing mechanisms but also extended to all aspects of numerical abilities. Overall, data from AD, in agreement with acquired disorders in focal lesioned patients, confirm the dissociations between multiple functional components of the number processing and calculation system.

Number-Stroop performance in normal aging and Alzheimer's-type dementia.

The number-Stroop paradigm was used to investigate changes in the inhibitory system and in numerical processing in healthy elderly and individuals with dementia of Alzheimers type (DAT). The size-congruity effect (i.e., relative to neutral trials, incongruent pairs interfere and/or congruent pairs facilitate either numerical or physical comparison) was found in all groups, though the pattern of interference and facilitation varied across them. Overall, the selective attention breakdown was reflected by the increase in interference shown by the older group and the DAT group. On the other hand, the observation of a standard laterality effect andof automatic numerical processing in all groups suggests that access and retrieval of numerical information is relatively resistant to cognitive deterioration.