Irene C. Mammarella

Imagery and spatial processes in blindness and visual impairment.

The objective of this review is to examine and evaluate recent findings on cognitive functioning (in particular imagery processes) in individuals with congenital visual impairments, including total blindness, low-vision and monocular vision. As one might expect, the performance of blind individuals in many behaviours and tasks requiring imagery can be inferior to that of sighted subjects; however, surprisingly often this is not the case. Interestingly, there is evidence that the blind often employ different cognitive mechanisms than sighted subjects, suggesting that compensatory mechanisms can overcome the limitations of sight loss. Taken together, these studies suggest that the nature of perceptual input on which we commonly rely strongly affects the organization of our mental processes. We also review recent neuroimaging studies on the neural correlates of sensory perception and mental imagery in visually impaired individuals that have cast light on the plastic functional reorganization mechanisms associated with visual deprivation.

Cognitive Abilities as Precursors of the Early Acquisition of Mathematical Skills During First Through Second Grades

The present longitudinal study was designed to investigate precursors of mathematics achievement in children. A total of 72 children were tested at both the beginning and end of first and second grades on measures of the following cognitive abilities: phonology, counting skills, short-term memory, working memory, and verbal and performance IQ. Path analysis models revealed differences in the variables predicting mathematics skills of first and second graders. Specifically, in first graders both short-term and working memory measures mediated the role of verbal IQ in predicting mathematics skills. Also, there was a direct relationship between performance IQ and mathematics at first grade. In contrast, in the longitudinal model, working memory measured both in first and second grades predicted mathematics achievement, whereas the relationship between performance IQ and mathematics disappeared. In conclusion, the results demonstrated that mathematics learning is predicted not by phonology or counting skills and that working memory is a plausible mediator in predicting mathematics achievement in primary school age children.

Evidence for different components in children's visuospatial working memory

There are a large number of studies demonstrating that visuospatial working memory (VSWM) involves different subcomponents, but there is no agreement on the identity of these dimensions. The present study attempts to combine different theoretical accounts by measuring VSWM. A battery composed of 13 tests was used to assess working memory and, in particular, the hypothesized mechanisms involved in the tasks, that is, active processing and passive recall of visual versus sequential-spatial versus simultaneous-spatial versus verbal tasks. The battery consisted of a number of tests already used in previous studies and new tests developed to examine specific components of working memory. We analysed the psychometric characteristics of the tests, the correlations amongst measured variables and estimated the measured variables with structural equation modelling in children attending third and fourth grades. Results revealed that the best model was composed of a specific verbal factor, three visuospatial passive factors (sequential-spatial, simultaneous-spatial, and visual) and one visuospatial active factor.

Selective Spatial Working Memory Impairment in a Group of Children With Mathematics Learning Disabilities and Poor Problem-Solving Skills

This study examines visual and spatial working memory skills in 35 third to fifth graders with both mathematics learning disabilities (MLD) and poor problem-solving skills and 35 of their peers with typical development (TD) on tasks involving both low and high attentional control. Results revealed that children with MLD, relative to TD children, failed spatial working memory tasks that had either low or high attentional demands but did not fail the visual tasks. In addition, children with MLD made more intrusion errors in the spatial working memory tasks requiring high attentional control than did their TD peers. Finally, as a post hoc analysis the sample of MLD was divided in two: children with severe MLD and children with low mathematical achievement. Results showed that only children with severe MLD failed in spatial working memory (WM) tasks if compared with children with low mathematical achievement and TD. The findings are discussed on the basis of their theoretical and clinical implications, in particular considering that children with MLD can benefit from spatial WM processes to solve arithmetic word problems, which involves the ability to both maintain and manipulate relevant information.

Spatial and visual working memory ability in children with difficulties in arithmetic word problem solving

Although various studies support the multicomponent nature of visuospatial working memory, to date there is no general consensus on the distinction of its components. A difference is usually proposed between visual and spatial components of working memory, but the individual roles of these components in mathematical learning disabilities remains unclear. The present study aimed to examine the involvement of visual and spatial working memory in poor problem-solvers compared with children with normal level of achievement. Fourth-grade participants were presented with tasks measuring phonological loop, central executive, and visual versus spatial memory. In two separate experiments, both designed to distinguish visual and spatial component involvement, poor problem-solvers specifically failed on spatial—but not visual or phonological—working memory tasks. Results are discussed in the light of possible working memory models, and specifically demonstrate that problem-solving ability can benefit from analysis of spatial processes, which involves ability to manipulate and transform relevant information; instead, no benefit is gained from the analysis of visual pictorial detail.

Spatial Working Memory and Arithmetic Deficits in Children With Nonverbal Learning Difficulties

Visuospatial working memory and its involvement in arithmetic were examined in two groups of 7- to 11-year-olds: one comprising children described by teachers as displaying symptoms of nonverbal learning difficulties (N = 21), the other a control group without learning disabilities (N = 21). The two groups were matched for verbal abilities, age, gender, and sociocultural level. The children were presented with a visuospatial working memory battery of recognition tests involving visual, spatial-sequential and spatial-simultaneous processes, and two arithmetic tasks (number ordering and written calculations). The two groups were found to differ on some spatial tasks but not in the visual working memory tasks. On the arithmetic tasks, the children with nonverbal learning difficulties made more errors than controls in calculation and were slower in number ordering. A discriminant function analysis confirmed the crucial role of spatial-sequential working memory in distinguishing between the two groups. Results are discussed with reference to spatial working memory and arithmetic difficulties in nonverbal learning disabilities. Implications for the relationship between visuospatial working memory and arithmetic are also considered.

Sequence and space: The critical role of a backward spatial span in the working memory deficit of visuospatial learning disabled children.

The clinical use of backward spatial short-term memory tasks, and in particular of the Corsi backward task, it has increased and it has generated a series of theoretical hypotheses. For example, it has been argued that (in its comparison with the forward version) it has the same implications as the backward digit span and/or it requires the use of amodal central executive components of working memory. This research tested the hypotheses that the backward spatial span does not involve the controlled use of the same type of sequential spatial processing involved in the forward version, that its impairment is modality specific, and that children with specific visuospatial learning disabilities (VSLD) have lower performance in backward than in forward Corsi Blocks test, compared to a control group. In Study 1, participants were administered a verbal span test (Digit Span test) and a visuospatial span test (Corsi Blocks task) both in the forward and backward versions, while in Study 2 only the Corsi test was administered. The comparison between the forward and backward span versions showed that both visuospatial learning disabled children (VSLD) and controls presented with the Digit Span had a lower performance with the backward version. However, for the Corsi task, this difference was present only for VSLD children. In fact, results revealed a significant impairment in the backward version of the Corsi test in the VSLD group, but not in the forward version, and in the Digit Span tasks. Results suggest that the Corsi backward task is not the spatial analogue of the Digit backward task and that it involves specific spatial processes.

Do working memory and susceptibility to interference predict individual differences in fluid intelligence

In the current study we examined the relationship between working memory capacity, inhibition/susceptibility to interference and fluid intelligence, measured by the Ravens Progressive Matrices (PM38), comparing groups of young (aged 18–35), young-old (aged 65–74), and old-old (aged 75–86) participants. Groups were administered two working memory tasks tapping into different mechanisms involved in working memory. The ability to control for irrelevant information was measured both considering memory errors (intrusion errors) in a working memory task and an index of susceptibility to interference obtained with a variant of the Brown-Peterson task. Regression analyses showed that the classical working memory measure was the most potent predictors of the Ravens score. Susceptibility to interference and intrusions errors contributed, but to a lower extent, to the Raven explained variance. These results confirm that working memory shares cognitive aspects with the fluid intelligence measure considered, whereas the role of inhibition to Raven scores is still in need of better evidence.

The involvement of working memory in children’s exact and approximate mental addition

The involvement of working memory (WM) was examined in two types of mental calculation tasks: exact and approximate. Specifically, children attending Grades 3 and 4 of primary school were involved in three experiments that examined the role of verbal and visuospatial WM in solving addition problems presented in vertical or horizontal format. For Experiment 1, the children were required to solve addition problems with carrying. For Experiment 2, they were required to solve addition problems without carrying. Then, for Experiment 3, the children needed to solve approximate problems with and without carrying. Results confirmed that different WM components are involved in solving mental addition problems. In Experiment 1, horizontally presented addition problems were more impaired than vertically presented ones, according to a verbal WM load; conversely, vertically presented addition problems were more affected by a visuospatial WM load, especially when the children were required to perform approximate calculations. In Experiment 2, this pattern emerged in neither exact nor approximate calculations. Finally, in Experiment 3, the specific involvement of WM components was observed only in problems with carrying. Overall, these results reveal that both approximate calculation and carrying procedures demand particularly high WM resources that vary according to the tasks constraints.

An analysis of the criteria used to diagnose children with Nonverbal Learning Disability (NLD)

Based on a review of the literature, the diagnostic criteria used for children with nonverbal learning disabilities (NLD) were identified as follows: (a) low visuospatial intelligence; (b) discrepancy between verbal and visuospatial intelligence; (c) visuoconstructive and fine-motor coordination skills; (d) visuospatial memory tasks; (e) reading better than mathematical achievement; and (f) socioemotional skills. An analysis of the effect size was used to investigate the strength of criteria for diagnosing NLD considering 35 empirical studies published from January 1980 to February 2011. Overall, our results showed that the most important criteria for distinguishing children with NLD from controls were as follows: a low visuospatial intelligence with a relatively good verbal intelligence, visuoconstructive and fine-motor coordination impairments, good reading decoding together with low math performance. Deficits in visuospatial memory and social skills were also present. A preliminary set of criteria for diagnosing NLD was developed on these grounds. It was concluded, however, that—although some consensus is emerging—further research is needed to definitively establish shared diagnostic criteria for children with NLD.