Working Memory and Cognitive Skills in Individuals with Down Syndrome

This work is aimed at analyzing working memory (WM) components and their relationships with other cognitive processes in individuals with Down syndrome (DS). Particular attention is given to examine whether a verbal WM deficit is due to difficulties in verbal abilities often showed by individuals with DS, or whether it is a deficit per se. A group of 20 individuals with DS was compared to a group of 20 typically developing (TD) children matched on vocabulary comprehension and to a group of 20 TD children matched on general verbal intelligence. The groups received a battery of 3 verbal and 3 visuospatial WM tasks requiring different degrees of control, and tests assessing verbal abilities (WPPSI verbal scale, PPVT), nonverbal skills (WPPSI performance scale), and logical thinking (LO). The results revealed that individuals with DS have deficits in both central executive (control) and verbal components of the WM system, and the latter one is independent of the general verbal abilities deficit. The data suggest that the development of central executive proceeds at a slower rate in individuals with DS and differently from TD children with comparable verbal abilities. The performance of individuals with DS on high-control WM tasks requires additional general resources that are strictly linked to intelligence.     

The Influence of a Visually-Rich Surrounding Environment in Visuospatial Cognitive Performance: A Study with Adolescents

ABSTRACT

Adolescence is a developmental period characterized by a complex maturation process of various cognitive abilities. Cognitive control, which includes response inhibition and working memory, is one of them. A typical study on response inhibition to visual stimuli presents distractors and targets on the same display (e.g., the computer screen). However, in most daily activities, the potential for distraction exists in the individuals’ surrounding environment. This study proposes an alternative experimental paradigm to investigate whether a high- vs. a low-load visual surrounding environment influences adolescents’ visuospatial performance. Sixty-four adolescents (aged 13–17 years) participated in two experimental sessions (one in a high-load and the other in a low-load visual surrounding environment) in which they responded to four visuospatial cognitive tasks (attention and memory). Overall, the results revealed lower performance when the tasks were performed in the high-load environment (e.g., fewer hits and correct responses, and more false alarms and errors). These results suggest that more attention should be devoted to the potential effect of the external environment in adolescents’ everyday activities. We discuss various areas to which these data might be of relevance and make suggestions for future directions of the proposed procedure.     

Visuospatial working memory in Turner's syndrome

Turner's syndrome is a genetic disorder, specific to women, in which one of the X chromosomes is partially or completely deleted. This syndrome is associated with physical features such as short stature or failure in primary and secondary sexual development, together with a specific pattern of cognitive functions. It has been suggested that women affected by Turner's syndrome perform poorly in tasks measuring visuospatial abilities and have a verbal IQ significantly higher than performance IQ. Although this result has received strong empirical support, the nature of the visuospatial deficit is still unclear. Recent studies on visuospatial processes have highlighted that the underlying cognitive structure is more complex than previously suggested and several dissociations have been reported (e.g., visual vs spatial, sequential vs simultaneous, or passive vs active processes). In the present study we analyze in detail the characteristics of the visuospatial deficit associated with Turner's syndrome by presenting four young women with a comprehensive battery of tasks designed to tap all aspects of visuospatial working memory. Results confirm that Turner's syndrome is associated with a general visuospatial working memory deficit, but the pattern of performance of different cases can be different, with a greater emphasis on active visuospatial processes. and on either sequential or simultaneous spatial processes.     

How are visuospatial working memory, executive functioning, and spatial abilities related? A latent-variable analysis.

This study examined the relationships among visuospatial working memory (WM) executive functioning, and spatial abilities. One hundred sixty-seven participants performed visuospatial short-term memory (STM) and WM span tasks, executive functioning tasks, and a set of paper-and-pencil tests of spatial abilities that load on 3 correlated but distinguishable factors (Spatial Visualization, Spatial Relations, and Perceptual Speed). Confirmatory factor analysis results indicated that, in the visuospatial domain, processing-and-storage WM tasks and storage-oriented STM tasks equally implicate executive functioning and are not clearly distinguishable. These results provide a contrast with existing evidence from the verbal domain and support the proposal that the visuospatial sketchpad may be closely tied to the central executive. Further, structural equation modeling results supported the prediction that, whereas they all implicate some degree of visuospatial storage, the 3 spatial ability factors differ in the degree of executive involvement (highest for Spatial Visualization and lowest for Perceptual Speed). Such results highlight the usefulness of a WM perspective in characterizing the nature of cognitive abilities and, more generally, human intelligence.     

Does relocating information in text depend on verbal or visuospatial abilities? An individual-differences analysis

In this individual-differences study, we evaluated the prevalent view that relocating information in a previously read text depends primarily on visuospatial abilities. Participants read a text, answered fillin-the-blank test questions, and identified which page and line in the original text contained the sentence in each question. They also completed a battery of verbal and visuospatial tasks. Performance on verbal tasks was highly predictive of the accuracy of both page and line identifications, and this correlation remained significant even after we controlled for performance on visuospatial tasks. In contrast, performance on visuospatial tasks was not predictive of either page or line identification accuracy, once verbal abilities were controlled for. These results suggest an important role for verbal abilities in relocation of text information and a lesser role for visuospatial abilities than has previously been assumed.     

Planning abilities and chess: A comparison of chess and non‐chess players on the Tower of London task

Playing chess requires problem‐solving capacities in order to search through the chess problem space in an effective manner. Chess should thus require planning abilities for calculating many moves ahead. Therefore, we asked whether chess players are better problem solvers than non‐chess players in a complex planning task. We compared planning performance between chess (N=25) and non‐chess players (N=25) using a standard psychometric planning task, the Tower of London (ToL) test. We also assessed fluid intelligence (Raven Test), as well as verbal and visuospatial working memory. As expected, chess players showed better planning performance than non‐chess players, an effect most strongly expressed in difficult problems. On the other hand, they showed longer planning and movement execution times, especially for incorrectly solved trials. No differences in fluid intelligence and verbal/visuospatial working memory were found between both groups. These findings indicate that better performance in chess players is associated with disproportionally longer solution times, although it remains to be investigated whether motivational or strategic differences account for this result.     

Can fast and slow intelligence be differentiated?

Responses to items from an intelligence test may be fast or slow. The research issue dealt with in this paper is whether the intelligence involved in fast correct responses differs in nature from the intelligence involved in slow correct responses. There are two questions related to this issue: 1. Are the processes involved different? 2. Are the abilities involved different? An answer to these questions is provided making use of data from a Raven-like matrices test and a verbal analogies test, and the use of a psychometric branching model. The branching model is based on three latent traits: speed, fast accuracy and slow accuracy, and item parameters corresponding to each of these. The pattern of item difficulties is used to draw conclusions on the cognitive processes involved. The results are as follows: 1. The processes involved in fast and slow responses can be differentiated, as can be derived from qualitative differences in the patterns of item difficulty, and fast responses lead to a larger differentiation between items than slow responses do. 2. The abilities underlying fast and slow responses can also be differentiated, and fast responses allow for a better differentiation between the respondents.     

Verbal, perceptual and intellectual factors associated with reading achievement in adolescents with cerebral palsy

31 adolescents with cerebral palsy were administered measures of verbal production, speech perception, nonverbal auditory perception, visuospatial perception and verbal intelligence as well as measures of reading recognition and reading comprehension. Nonverbal auditory perception and verbal intelligence were most highly correlated with both reading measures despite the fact that most subjects were most severely impaired in visuospatial perception.     

Turner Syndrome: A Review of Genetic and Hormonal Influences on Neuropsychological Functioning

Turner syndrome (TS) is a genetic disorder in females that arises from the loss of X chromosome material. Affected individuals demonstrate a characteristic neuropsychological profile of strengths in verbal processing and weaknesses in visuospatial processing, consistent with the Nonverbal Learning Disabilities syndrome. Previous research has described a wide range of visuospatial deficits in TS; however, their verbal abilities are less extensively studied. The present paper describes the processing difficulties of a 9-year-old girl with TS who demonstrated problems in integrating details of a complex visual display and using organizational terms to describe visual scenes or events. Her specific cognitive disabilities were thought to underlie some of the social and behavioral problems she was currently experiencing. Her pattern of results is consonant with the neuropsychological pattern that others have attributed to right hemisphere dysfunction and/or white matter abnormality.     

Visual integration difficulties in a 9-year-old girl with Turner syndrome: parallel verbal disabilities?

Turner syndrome (TS) is a genetic disorder in females that arises from the loss of X chromosome material. Affected individuals demonstrate a characteristic neuropsychological profile of strengths in verbal processing and weaknesses in visuospatial processing, consistent with the Nonverbal Learning Disabilities syndrome. Previous research has described a wide range of visuospatial deficits in TS; however, their verbal abilities are less extensively studied. The present paper describes the processing difficulties of a 9-year-old girl with TS who demonstrated problems in integrating details of a complex visual display and using organizational terms to describe visual scenes or events. Her specific cognitive disabilities were thought to underlie some of the social and behavioral problems she was currently experiencing. Her pattern of results is consonant with the neuropsychological pattern that others have attributed to right hemisphere dysfunction and/or white matter abnormality.     

A Neuropsychological Approach to Intelligence

This paper proposes that current psychometric intelligence tests are limited in evaluating cognitive activity. From a neuropsychological perspective, they fail to measure some fundamental cognitive abilities such as executive functions, memory, and visuospatial abilities. The analysis of the Wechsler Intelligence Scale presented shows that the original rationale for selecting the specific subtests included in the WAIS was unclear. The concept of a g factor in cognition is also analyzed, with the conclusion that the g factor continues to be controversial. The value of intelligence tests in predicting school performance is also criticized. It is proposed that the psychometric concept of general intelligence should be deleted from cognitive and neurological sciences. Finally, it is proposed that, in the future, neuropsychological instruments sensitive to more specific cognitive abilities replace current psychometric intelligence tests.     

Visuospatial over verbal demands in predicting Tower of London planning tasks

The role of verbal and visuospatial information processing in Tower of London (TOL) tasks was investigated. The first part of the investigation examined the verbal and visuospatial abilities and preferred cognitive style (visualizer vs. verbalizer) of 79 participants, in an inter-individual differences approach. Visuospatial abilities significantly predicted TOL performance, but the impact of cognitive style was negligible. The second part applied a dual-task manipulation of concurrent interference of TOL planning tasks on verbal and visuospatial memory, using the same participants. Concurrent processing of the TOL tasks diminished visuospatial memory performance considerably but had no effect on verbal memory, and there was no interaction between cognitive style and memory. These findings clearly underscore the role of visuospatial information processing in TOL tasks and indicate little bearing of verbal or visual cognitive style on TOL problem solving. These results have important implications for TOL and cognitive style in clinical application and cognitive neuroimaging research.     

Decision-making competence and cognitive abilities: Which abilities matter?

Decision-making competence is a skill that is associated with numerous positive life outcomes. Even though multiple cognitive abilities have been shown to predict decision-making competence, few studies have incorporated a large test battery tapping into several cognitive abilities concurrently in the same models. The current paper presents a study that sought to investigate which cognitive abilities predicted overall decision-making competence in adults using hierarchical regression analysis. A cognitive test battery, comprising abilities such as general intelligence, executive functions, numeracy, visuospatial ability, and time perception, was administered to 182 participants. Results indicate that both general intelligence, which was consistently the strongest predictor, and numeracy contributed independently to overall decision-making competence. Executive functions did predict overall decision-making competence, while all predictors were included in the models. A novel finding concerns the relationship between time perception and decision-making competence. The complementary roles of these cognitive abilities are discussed.     

Knox's cube imitation test: a historical review and an experimental analysis

The cube imitation test was developed by as a nonverbal test of intelligence. Many variants show satisfactory reliability, but performance is correlated both with Verbal IQ and with Performance IQ. Performance is impaired by cerebral lesions but unrelated to the side of lesion. Examinees describe both verbal and visuospatial strategies. In a new experiment, performance was disrupted by concurrent random generation, manual tapping, and articulatory suppression. The cube imitation test is not simply a measure of the ability to retain visuospatial information but also depends on verbal representations as well as attentional capacity. Even so, the test was central to the modern appreciation that any adequate measure of intelligence must incorporate both verbal tests and performance tests.     

Race differences in behaviour: A review and evolutionary analysis

Racial differences exist on numerous heritable behaviour traits such that Caucasoids fall between Mongoloids and Negroids. Across samples, ages, and time periods, this pattern is observed on estimates made of brain size and intelligence (cranial capacity=1448, 1408, 1334 cm^3., brain weight=1351, 1336, 1286 g; IQ scores=107, 100, 85); maturation rate (age to walk alone, age of puberty, age of death); personality and temperament (activity level, anxiety, sociability); sexual restraint (gamete production, intercourse frequency, size of genitalia); and social organization (marital stability, mental health, law abidingness). These observations may be explained in part in terms of gene-culture coevolutionarily based r/K reproductive strategies.     

Race, brain size, and intelligence: a reply to Cernovsky

Cernovsky's 1990 critique of my work on the relation between brain size and IQ inadequately presents my position. I did not address the issue of sex differences in brain size nor did I conclude that "women are less intelligent than men" (p. 337). In the autopsy study cited by Cernovsky, it was concluded that, when body size is controlled, the male-female difference in brain size is removed but the black-white difference in brain size remains. Cernovsky also ignores much additional data, including that Mongoloid populations have larger and heavier brains than Caucasoids. Here, I review evidence on the relation between (a) brain size and race and (b) brain size and intelligence. Data are also tabulated for personality, speed of maturation, and sexuality, on all of which the Caucasoid average consistently falls between those of Mongoloids and Negroids. This ordering may be explained by a gene-based evolutionary theory of r/K reproductive strategies in which Mongoloids are more K-selected than Caucasoids and Caucasoids more than Negroids.     

Differential K theory and race differences in E and N

Differential K Theory was recently proposed relating personality to reproductive strategy (Rushton, 1985). The more K the person is (the symbol derives from population biology), the more he or she will delay reproductive effort, produce fewer children and more intensely care for them. Concomitant characteristics include intelligence, altruism, law-abidingness and behavioural restraint. Race differences are hypothesized such that, in terms of K, Mongoloids > Caucasoids > Negroids. Barratt and Eysenck (1984) recently published standardized Extraversion (E), Neuroticism (N), Psychoticism (P) and Social Desirability (L) scores for males and females from 25 different countries, but did not analyse the data in such a way that racial differences were found. In the current study Barratt and Eysenck's data are aggregated across sex and over countries to examine whether theoretical predictions regarding race differences in behavioural restraint do in fact occur. Behavioural restraint was indexed by low E and high N scores. The means for 8 Mongoloid samples (N = 4044) were contrasted with those of 38 Caucasoid (N = 19, 807) and 4 Negroid ones (N = 1906), and the resultant comparisons confirmed expectations. Mongoloids are lower on E and higher on N than Caucasoids, who in turn are lower in E and higher on N than Negroids.     

The structure of Japanese abilities: An analysis in terms of the hierarchical model of intelligence

The structure of Japanese abilities is analyzed in terms of the Burt-Vernon hierarchical model of intelligence. The data are derived from the Japanese standardization of theWechsler Intelligence Scale for Children-Revised. It is found that Japanese children are marginally but significantly superior to white American children on Spearman’sg. Japanese children are inferior on the group verbal factor but superior on the group perceptual factor. On the primary abilities, Japanese children are inferior on verbal comprehension and perceptual speed and superior on memory span, number, and spatial ability. It is suggested that this pattern of Japanese cognitive strengths and weaknesses helps to clarify a number of conflicting findings on Japanese intelligence.     

On Intelligence IV: Toward a restoration of general intelligence

The present paper points to the limitations of a focusing on narrow primary factors of intelligence and argues for broad-factor structuring of ability data. Recent studies of such broad attributes would suggest a "rapprochement" between Spearman's general intelligence model and Cattell's theory of Fluid and Crystallized Intelligence. Discussing the neo-Spearman organization of abilities thus proposed, the paper argues, however, that the conceptualization of intelligence suggested by this structural model is more akin to Thomson's "sampling" model than to the "power" model of both Spearman and Cattell. The possible role of these interpretations of ability data in future research on intelligent behavior is discussed.     

Interference between verbal concept formation and spatial mental rotation in female subjects

In this study the relation between spatial cognition and verbal intelligence abilities was examined in case of 52 women. Interference between mental rotation performance and verbal intelligence scores was found. Women with good verbal abilities have lower scores in mental rotation tasks than subjects with poorer verbal abilities. This finding is in accordance with some basic models of a dual-coding system. The spatial functions represented in mental rotation interfered with verbal-based concept formation and lexical knowledge in college women.