Sex differences in clerical speed: Perceptual encoding vs. verbal encoding

Most interpretations of sex differences on clerical speed tests have emphasized the role of rapid perception of details and shifts in attention. Some have emphasized comparison and decision processes. Sex differences in speeded, successive matching were studied in four experiments with college students. The experimental task involved the successive identification of stimulus items presented in lists by tapping matching items on response cards. Sex differences were found to be related to response-card content and not to stimulus-list content. When the identification response involved tapping words, colors, or directional symbols, females were significantly faster than males; however, when the identification response involved tapping shapes, no significant sex differences were found. Results indicated that sex differences in some aspect of short-term memory may also be involved. Earlier interpretations of sex differences on speeded matching tasks in terms of such global concepts as perceptual speed are believed to be inadequate. An alternative explanation is discussed emphasizing verbal encoding, memory, and evaluation processes.     

The role of mathematical skill in sex differences on Raven’s Matrices

This study replicated a previously reported male advantage on certain items of Raven’s Matrices and found no sex differences in performance on other items. We refer to the latter as analytic (1) items and the former as analytic (2) items. Reasons for the male advantage were investigated by correlating scores obtained by male and female high school students on analytic (1) and analytic (2) items with their scores on tests of spatial, verbal and mathematical ability. There were no sex differences in the magnitude of the correlations between scores on analytic (2) items and the two spatial and verbal tests. In contrast, males but not females showed a significantly higher correlation of maths with analytic (2) than with analytic (1). The results suggest the Raven’s Matrices may engage different, more specific cognitive processes in males and more general cognitive processes in females.     

Sex differences in the association of math achievement with visual-spatial and verbal working memory: Does the type of math test matter?

Previous research on sex differences in mathematical achievement shows mixed findings, which have been argued to depend on types of math tests used and the type of solution strategies (i.e., verbal versus visual-spatial) these tests evoke. The current study evaluated sex differences in (a) performance (development) on two types of math tests in primary schools and (b) the predictive value of verbal and visual-spatial working memory on math achievement. Children (N = 3175) from grades 2 through five participated. Visual-spatial and verbal working memory were assessed using online computerized tasks. Math performance was assessed five times during two school years using a speeded arithmetic test (math fluency) and a word problem test (math problem solving). Results from Multilevel Multigroup Latent Growth Modeling, showed that sex differences in level and growth of math performance were mixed and very small. Sex differences in the predictive value of verbal and visual-spatial working memory for math performance suggested that boys seemed to rely more on verbal strategies than girls. Explanations focus on cognitive and emotional factors and how these may interact to possibly amplify sex differences as children grow older.     

HEMISPHERE FUNCTION AND SPATIAL ABILITY: AN EXPLORATORY STUDY OF SEX AND CULTURAL DIFFERENCES

Three experiments investigated performance as a function of the visual hemifield to which verbal and spatial stimuli were presented tachistoscopically. The aim was to relate laterality effects to individual, sex and cultural differences in spatial ability within the framework of a model of hemispheric specialisation. A left-hemisphere advantage for verbal materials was obtained but no advantage for right-hemisphere presentation of visuospatial information occurred in the following samples: British and Ghanaian (experiment 1), high and low spatial ability groups (experiment 2) and males and females (experiment 3). Traditional spatial ability tests had no predictive value for performance on the tachistocopic tasks and an interaction between presentation field and responding hand was interpreted as implying equivalent processing of spatial information in either hemisphere.     

Socioeconomic status modifies the sex difference in spatial skill

We examined whether the male spatial advantage varies across children from different socioeconomic (SES) groups. In a longitudinal study, children were administered two spatial tasks requiring mental transformations and a syntax comprehension task in the fall and spring of second and third grades. Boys from middle- and high-SES backgrounds outperformed their female counterparts on both spatial tasks, whereas boys and girls from a low-SES group did not differ in their performance level on these tasks. As expected, no sex differences were found on the verbal comprehension task. Prior studies have generally been based on the assumption that the male spatial advantage reflects ability differences in the population as a whole. Our finding that the advantage is sensitive to variations in SES provides a challenge to this assumption, and has implications for a successful explanation of the sex-related difference in spatial skill.     

A Sex Difference on a Novel Spatial Working Memory Task in Humans

Neurophysiological and behavioral evidence suggests that the prefrontal cortex (PFC) may be sexually differentiated in nonhuman primates. The present study examined whether there are sex differences in working memory in humans that might reflect sexual differentiation of human PFC. Male and female undergraduates were administered a novel multitrial spatial working memory task (SPWM) and a verbal working memory task. In three experiments, females committed significantly fewer working memory errors and took significantly less time to reach criterion than males on the SPWM task. The female advantage was not accounted for by differences in general intellectual ability, attention, perceptual speed, incidental memory, or speed of verbal access. In Study 3, a sex difference was also observed on a measure of verbal working memory. The findings suggest that some prefrontal functions may be sexually differentiated in humans.     

Converging evidence that visuospatial cognition is more age-sensitive than verbal cognition

In 3 separate experiments, the same samples of young and older adults were tested on verbal and visuospatial processing speed tasks, verbal and visuospatial working memory tasks, and verbal and visuospatial paired-associates learning tasks. In Experiment 1, older adults were generally slower than young adults on all speeded tasks, but age-related slowing was much more pronounced on visuospatial tasks than on verbal tasks. In Experiment 2, older adults showed smaller memory spans than young adults in general, but memory for locations showed a greater age difference than memory for letters. In Experiment 3, older adults had greater difficulty learning novel information than young adults overall, but older adults showed greater deficits learning visuospatial than verbal information. Taken together, the differential deficits observed on both speeded and unspeeded tasks strongly suggest that visuospatial cognition is generally more affected by aging than verbal cognition.     

Sex differences for selective forms of spatial memory

In the present study, a systematic comparison of sex differences for several tests of spatial memory was conducted. Clear evidence for more accurate male performance was obtained for precise metric positional information in a wayfinding task and in an object location memory task. In contrast, no sex difference characterized topological information processing (object-to-position assignment). Together, these findings provide further insight in the specificity of sex differences in spatial memory and in the functional architecture of spatial memory. Implications for the relevant evolutionary basis are discussed.     

Sex and cross-cultural differences in the estimated multi-faceted intelligence quotient score for self, parents and siblings

Over four hundred young people from Britain, Hawaii and Singapore estimated their own, their parents and their siblings IQ score on each of Gardner (1983) fundamental human intelligences: verbal (linguistic), logical (mathematical), spatial, musical, body-kinesthetic, interpersonal and intrapersonal. They also answered six simple questions concerning intelligence tests. There were both cultural and sex differences in the estimation of overall own intelligence score. Males gave higher scores than females (109 vs 107) while the British gave the highest score (109) compared with the Singaporeans (106) and Hawaiians (104). Factor analysis of the seven dimensions yielded either a two or three factor solution, the latter being verbal (verbal, inter-intrapersonal), mathematical (mathematical and spatial), and musical (musical, body-kinesthetic). There were consistent sex differences in the estimations of the three factors for self, but not of parents, and only marginally of sisters. Males more than females, and the British more than the other groups, were more likely to believe in sex and race difference in intelligence.     

A male advantage for spatial and object but not verbal working memory using the n-back task

Sex-related differences have been reported for performance and neural substrates on some working memory measures that carry a high cognitive load, including the popular n-back neuroimaging paradigm. Despite some evidence of a sex effect on the task, the influence of sex on performance represents a potential confound in neuroimaging research. The present study investigated sex-related differences in verbal, spatial, and common object versions of the high cognitive load "n-back" working memory task. Eighteen male and 18 female undergraduates completed all 3 versions of the task. A mixed ANOVA, with Sex (male and female) as the between-subjects factor and Condition (verbal, spatial, and object) as the within-subjects repeated measure revealed that males were significantly more accurate than females on the spatial and object versions of the n-back task and performed equivalently to females on the verbal version of the task. Although the expected female advantage for verbal working memory was not found using this effortful n-back task, these results support a male advantage for high cognitive load spatial and object working memory. Future research should take into account the influence of sex on performance of the n-back task, and examine sex-related differences in working memory using other paradigms.     

Simultaneity in Processing of Verbal and Spatial Information

Recent studies involving recall of verbal and spatial information produced conflicting results. In some cases investigators found males recalled verbal and spatial information equally well whereas females did less well on spatial than verbal information, but in other cases no sex differences were found. They also differed in that one study found processing of verbal and spatial information to be independent whereas others suggested trade-offs might occur. Using college-age subjects (17-25 yrs) with equal numbers of males and females (total n = 186) two experiments were performed to examine these differences. Although overall differences were found favoring verbal recall, females’ recall of spatial information was relatively poorer than males. Using a procedure designed to avoid possible artifactual depression of combined performance, we concluded that processing of spatial and verbal information is simultaneous in nature.

     

Reported head injury and sex differences in color naming, color matching, and digit-string matching.

It was hypothesized that the observed sex differences on three speeded tasks could be accounted for in terms of the greater incidence of head injury in men than in women. In two studies of 64 male and 66 female college students significant sex differences were found on digit-string matching and color-matching tasks. When the data from those 39 subjects with reported histories of head injury were eliminated from the analysis or head-injury reports were statistically controlled, significant sex differences remained. Digit-string matching times were significantly correlated with reported head injury in both studies, suggesting that this test is sensitive to residual effects of head injury.     

A study of the dynamics of sex differences in adulthood

Studies of gender differences using primarily young individuals show that males, on average, perform better than females in physical activities but worse than females on tests of verbal abilities. There is however a controversy about the existence of these sex differences in adulthood. Our study used 1271 participants from four cultural backgrounds (Chinese, multi‐generation Canadians, Indu‐Canadians, and European‐Canadians) divided in five age groups. We measured sex differences in the time required for participants to complete a lexical task experiment, and also assessed their verbal tempo and physical endurance using a validated temperament test (Structure of Temperament Questionnaire). We found a significant female advantage in time on the lexical task and on the temperament scale of social–verbal tempo, and a male advantage on the temperament scale of physical endurance. These sex differences, however, were more pronounced in young age groups (17–24), fading in older groups. This “middle age–middle sex” phenomenon suggests that sex differences in these two types of abilities observed in younger groups might be “a matter of age,” and should not be attributed to gender in general. A one‐dimensional approach to sex differences (common in meta‐analytic studies) therefore overlooks a possible interaction of sex differences with age.     

Age effects in coding tasks: componential analysis and test of the sensory deficit hypothesis

Multiple forms of a symbol-digit substitution task were used to provide a componential analysis of age differences in coding task performance. The results demonstrated age differences in feature encoding, memory, and visual search. A 2nd experiment was conducted with young adults to investigate a sensory deficit as a locus of age differences. The spatial contrast sensitivity deficit of older adults was simulated on forms by applying a digital filter. Persons in the age-simulated contrast condition performed worse than those in the normal contrast condition. The stimulus degradation effect was linked to visual search speed. The study illustrates the utility of componential analysis and offers direct support for the hypothesis that sensory deficits affect performance on tasks used to assess intelligence.     

Information processing components of substitution test performance

Although substitution tests have been included in tests of intelligence for years, the underlying abilities they measure have still not been clearly determined. This study used componential analysis to investigate the information-processing components underlying substitution test performance. The bases of sex and age differences were also of interest. One hundred subjects from each of three age groups (9–11, 18–25, and 60–89 years) were tested.The componential analysis found that substitution tests measure perceptual speed and, to a lesser extent, memory ability and writing speed. The component “Stimulus Orientation, Response Initiation, and Execution” was related to substitution test performance in the sample of children and the sample of older adults but not in the sample of younger adults. Verbal ability was not significantly related to substitution test performance in the two younger samples but was strongly related to substitution performance in the oldest sample. Although females outperformed males on the Symbol Digit Test, males did as well as females on the computerized tasks. Apparently, sex differences in substitution test performance cannot be explained by the components of the test measured here.     

Individual differences in spatial relation processing: effects of strategy, ability, and gender

Numerous studies have focused on the distinction between categorical and coordinate spatial relations. Categorical relations are propositional and abstract, and often related to a left hemisphere advantage. Coordinate relations specify the metric information of the relative locations of objects, and can be linked to right hemisphere processing. Yet, not all studies have reported such a clear double dissociation; in particular the categorical left hemisphere advantage is not always reported. In the current study we investigated whether verbal and spatial strategies, verbal and spatial cognitive abilities, and gender could account for the discrepancies observed in hemispheric lateralization of spatial relations. Seventy-five participants performed two visual half field, match-to-sample tasks (Van der Ham, van Wezel, Oleksiak, & Postma, 2007; Van der Ham, Raemaekers, van Wezel, Oleksiak, and Postma, 2009) to study the lateralization of categorical and coordinate relation processing. For each participant we determined the strategy they used in each of the two tasks. Consistent with previous findings, we found an overall categorical left hemisphere advantage and coordinate right hemisphere advantage. The lateralization pattern was affected selectively by the degree to which participants used a spatial strategy and by none of the other variables (i.e., verbal strategy, cognitive abilities, and gender). Critically, the categorical left hemisphere advantage was observed only for participants that relied strongly on a spatial strategy. This result is another piece of evidence that categorical spatial relation processing relies on spatial and not verbal processes.     

Sex differences in cognition: the role of testosterone and sexual orientation

The performance of both heterosexual and homosexual males and females was compared on four cognitive tasks which have been shown to reveal evidence of sexual dimorphism. In one spatial and one verbal task, significant sex and orientation effects were found. Significant relationships were also found between salivary free-testosterone levels and performance on both spatial tasks, but no significant associations were found for performance on the two verbal tasks. The present study revealed both within- and between-sex differences in cognition and indicates that these differences may be partly accounted for by the activational effects of free testosterone.     

An exploration of the verbal encodability hypothesis for sex differences in the digit-symbol (symbol-digit) test

Two experiments were conducted to allow a test of Estes' verbal encodability hypothesis regarding female Digit-Symbol test superiority. Experiment 1 demonstrated significant differences in the relative encodability of various sets of symbols both in the time required to produce verbal associates and in quantitative measures of the uncertainty regarding what associate would be produced. Experiment 2 utilized these symbols to assess the stability of female superiority on a Symbol-Digit task across levels of verbal encodability. Predictions were that females should perform significantly better than males on tests with symbols that are easily encoded verbally, but there should be no significant sex difference when symbols are difficult to encode verbally. Significant effects for sex, task, and their interaction were found. However, the verbal encodability hypothesis is rejected for one favoring perceptual speed, due to the pattern of female superiority on the tests, and the nature of intrasex correlations. Results also show that traditional female supremacy on the Digit-Symbol carries over to the Symbol-Digit format when easily discriminable symbols are used.     

No sex differences in spatial location memory for abstract designs

Previous research has demonstrated a female advantage, albeit imperfectly, on tests of object location memory where object identity information is readily available. However, spatial and visual elements are often confounded in the experimental tasks used. Here spatial and visual memory performance was compared in 30 men and 30 women by presenting 12 abstract designs in a spatial array for recall and recognition (visual memory) and spatial location ("object" location memory). Object location memory was measured via a sensitive absolute displacement score defined as the distance in mms between the position assigned to the object during recall and the actual position it originally occupied. There were no sex differences in either the visual or spatial location tests. Controlling for age and estimated IQ scores made no impact on the results. These data suggest an absence of a sex difference in purely visual and spatial aspects of object location memory.