Family handedness as a predictor of mental rotation ability among minority girls in a math-science training program.

Right-handed girls from nonright-handed families outperformed the other groups of minority adolescent girls enrolled in a science and technology program on a test of mental rotation ability. This target group excelled over right-handed girls with all right-handed relatives and nonright-handers. The pattern of group differences in mental rotation ability found here is consistent with those found for women with math-science training at the college level. The minority boys in the program outperformed the girls as a whole, but did not differ significantly from the right-handed girls with nonright-handed relatives. The present findings provide further support for the generality of Annett's genetic theory of handedness and brain organization, and for the interaction of genetic and environmental factors in accounting for individual differences in mental rotation ability.     

Evidence in support of a model that predicts how biological and environmental factors interact to influence spatial skills.

It was proposed, based on M. Annett (1985), that individuals biologically predisposed to poorer spatial skills are less likely to capitalize on opportunities to develop these skills. Using an analysis of variance design assessing mental rotation skills in 2 cohorts of 8th graders (365 students), the authors found a significant 3-way interaction (Brothers x Family Handedness x Gender). For the girls with brothers, those from all right-handed families had lower mental rotation scores than did the other girls. For the 2nd cohort, among those children who participated in mental-rotation-type activities with their brothers, both boys and girls from all right-handed families performed more poorly on the mental rotation test than did the other children with brothers. Thus, compared with other children, the children from all right-handed families do not appear to be able to use their spatial experiences with male siblings to increase their spatial skills.     

Dyslexia and handedness: developmental phonological and surface dyslexias are associated with different biases for handedness

Developmental disorders of reading and spelling have long been associated with increased left- and mixed-handedness but the evidence has been controversial. The right shift (RS) theory of handedness and cerebral dominance, developed by Annett from 1972 onward, offers resolutions to several puzzles about laterality in the so-called dyslexias. This review of findings in the light of the theory shows that "phonological" dyslexics are less likely to be right-handed, while "surface" or "dyseidetic" dyslexics are more likely to be right-handed than the general population.     

Sex differences in spatial ability: a lateralization of function approach

The current study was designed to examine whether the extent of the male advantage in performance on a spatial task was determined by the extent to which the task was right-hemisphere dependent. Participants included 108 right-handed men and women who completed the mental rotation, waterlevel, and paperfolding tasks, all of which were presented bilaterally. The results partially supported the hypothesis. On the mental rotation task, men showed a right-hemisphere advantage, whereas women showed no hemispheric differences; however, no overall sex differences were observed. On the waterlevel task, men outperformed women, and both men and women showed a right-hemisphere advantage. On the paperfolding task, no sex or hemispheric differences were observed. Although the findings of the current study were mixed, the study provides a framework for examining sex differences across different types of spatial ability.     

Gender Differences in Spatial Task Performance as a Function of Speed or Accuracy Orientation

Performance differences in spatial abilities as a function of gender may be modified by practice and relevant background experiences, as well as by directions given in laboratory situations. We examined whether a focus on speed or accuracy influenced performance in various spatial domains, using several different scoring techniques. Men and women from a small, predominantly White private college completed tasks of spatial perception, spatial visualization, and mental rotation under one of three conditions: speed-emphasis, accuracy-emphasis, or control. Participants also provided information concerning experiences pertinent to spatial ability. Results revealed relative parity between men and women on tasks of spatial visualization and spatial perception; speed/accuracy orientation did not alter these findings. Men outperformed women on mental rotation, but only when scored in a strict manner and when explicitly told to focus on accuracy, but not when directional emphasis was absent or geared toward speed. Self-reported background in math, sports, and the arts was unrelated to performance. The results are discussed in terms of women's efficacy beliefs about performing tasks explicitly designated as spatial in nature.     

Sex differences and handedness in hemispheric lateralization of tactile-spatial functions

Sex differences in spatial processing and handedness were studied with a tactile-spatial task in 27 male and 29 female right-handed undergraduate students in psychology. Subjects were asked to identify amorphous shapes to investigate possible male right-hemisphere specialization for spatial functions and bilateral representation among the women. The Annett handedness questionnaire estimated extent of right-handedness. Subjects were classified by major, and women by phase of menstrual cycle. Analysis shows significantly more right-handedness in women and ambidexterity in men. Over-all, men do not perform significantly better than women, although men outperform women with their left hands when handedness is covaried. Within sex, no difference is seen between left and right hand scores for men, but women perform significantly better with right than left hands. Further analyses suggest men appear right-hemisphere dominant for this task whereas women show left-hemisphere dominance. Analyses of hormonal data support recent research, in that for women on the pill there is a trend to perform worse than all other groups. Engineering students perform significantly better than all other majors.     

Independence of hand preference and sex-linked genetic effects on spatial performance.

The paper-and-pencil spatial performance of right- and left-handed high school students was compared separately for 1236 males and 1241 females. Handedness differences in favor of right-handed subjects were found among males only. Analysis of data for a subgroup of 555 subjects indicated that handedness and sex-linked genetic effects acted independently and additively on spatial performance.     

The sensed presence within experimental settings: implications for the male and female concept of self

The sense of "a presence" or of a sentient being during partial sensory deprivation and exposure to very weak, complex magnetic fields across the cerebral hemispheres may be a normal neurocognitive experience that is associated with the brief intrusion of the right hemispheric homologue of the left hemispheric (and strongly linguistic) sense of self into awareness. Within an optimal experimental setting, women reported more frequent experiences of a sensed presence than did men, and men were more likely than women to consider these experiences as "intrusions" from extrapersonal or ego-alien sources. Both effects were predicted by the vectorial hemisphericity hypothesis and the known neurocognitive differences between right-handed men and right-handed women. Sociobiological implications for gender differences in the probability of intercalation between distinctive processes within the left and right temporoparietal lobes are discussed.     

Spatial ability and handedness

The relationship between preferred handedness and spatial visualization was examined for 124 female and 229 male undergraduate students. Handedness and spatial ability were used in the design as continuous variables. Other variables examined were sex of subject and family history of sinistrality. Spatial ability was found to be systematically related to measured handedness, familial left-handedness, and sex of subject. Males outperformed females at all levels of handedness. The lowest performance was obtained by subjects who were either extremely left-handed or extremely right-handed. The highest scores were obtained by individuals with left-handed relatives and whose handedness scores were in the range considered mixed or slightly right-handed. The results suggest that decreased hemispheric specialization is associated with increased spatial ability.     

Frequency-dependent performance and handedness in professional baseball players (Homo sapiens)

I used data on handedness and pitching and hitting performance in annual cohorts of professional baseball players (1957-2005) to test the hypothesis that handedness among pitchers was subject to negative frequency-dependent selection. As predicted by this hypothesis, right-handed pitchers were more successful (i.e., opposing batters hit more poorly against them) when they were relatively rare in the population. Contrary to the predictions of this hypothesis, however, left-handed pitchers were more successful when they were relatively common. Both right- and left-handed batters performed better in years dominated by right-handed pitchers, despite the fact that right-handed batters perform relatively poorly against right-handed pitchers. I suggest that batters form cognitive representations based on pitcher handedness, and that these representations are strengthened by repeated exposure or priming. When the pitcher handedness polymorphism is more balanced (e.g., 67% right-handed, 33% left-handed), these cognitive representations are less effective, which leads to decreased batting averages and improved performance by all pitchers. Furthermore, these cognitive representations are likely to be more critical to the success of right-handed hitters, who have reduced visuomotor skills relative to left-handed hitters.     

An investigation of immune system disorder as a "marker" for anomalous dominance

Geschwind and Galaburda (1987) proposed that immune disorder (ID) susceptibility, along with left handedness and familial sinistrality (FS), is a "marker" for anomalous dominance. The theory predicts lesser left lateralization for language processes, lessened left hemisphere abilities, and enhanced right hemisphere abilities. We assessed language laterality (dichotic consonant vowel task) and performances on spatial and verbal tasks. Subjects were 128 college students. The factors of handedness, sex, FS, and immune disorder history (negative or positive) were perfectly counterbalanced. Left-handers were significantly less lateralized for language and scored lower than right-handers on the spatial tasks. Females scored lower on mental rotation than males, but performed comparably to males on the spatial relations task. The only effect of ID was by way of interaction with FS on both spatial tasks--subjects who were either negative or positive on both FS and ID status factors scored significantly higher than subjects negative for one but positive for the other factor. A speculative explanatory model for this interaction was proposed. The model incorporates the notion that FS and ID factors are comparably correlated, but in opposite directions, with hormonal factors implicated by other research as relevant for spatial ability differences. Finally, no support for the "anomalous dominance" hypothesis predictions was found.     

Real three-dimensional objects: effects on mental rotation

The current experiment investigated real three-dimensional (3D) objects with regard to performance on a mental rotation task and whether the appearance of sex differences may be mediated by experiences with spatially related activities. 40 men and 40 women were presented with alternating timed trials consisting of real-3D objects or two-dimensional illustrations of 3D objects. Sex differences in spatially related activities did not significantly influence the finding that men outperformed women on mental rotation of either stimulus type. However, on measures related to spatial activities, self-reported proficiency using maps correlated positively with performance only on trials with illustrations whereas self-reported proficiency using GPS correlated negatively with performance regardless of stimulus dimensionality. Findings may be interpreted as suggesting that rotating real-3D objects utilizes distinct but overlapping spatial skills compared to rotating two-dimensional representations of 3D objects, and real-3D objects can enhance mental rotation performance.     

Familial handedness and spatial ability: a study with Chinese students aged 14-24

This study tested Annett's right-shift theory on spatial ability with two samples from China. The Vandenberg Mental Rotation Test (MRT), Edinburgh Handedness Inventory, and Family Handedness Questionnaire were administered to 266 high school students and 297 undergraduates. We found very few r++ or r-- among Chinese students. Most Chinese are either moderately right-handed or ambidextrous. Consistent with Casey's finding, we found using different methods to classify handedness leads to different conclusions. However, we did not find the effect of familial handedness that Casey found. Visual strategy is related to success on the MRT but handedness is not.     

Girls who use "masculine" problem-solving strategies on a spatial task: proposed genetic and environmental factors.

This study investigated strategy and performance differences between right-handed boys and girls on a mental rotation task. Based on predictions from Casey and Brabeck's (1990) theory of sex differences, the study was also designed to identify a target group of right-handed girls with the optimal combination of genetic and environmental factors (high math/science achievers with nonright-handed immediate relatives). They were predicted to show strategies and performance more similar to those of the boys than to those of both the low math/science achieving girls and the high math/science girls with all right-handed immediate relatives (predicted to have the nonoptimal genotype). Strategy preference was measured using selective interference, whereby subjects solved mental rotation items concurrently with either verbal or visual-spatial interference tasks. Group comparisons were made on the amount of decrement in mental rotation performance as a result of the two types of interference tasks. This provided a basis for comparing the groups on the use of visual-spatial or verbal strategies on the mental rotation task. The boys: (1) did not show a significant advantage over the girls on the mental rotation items, but (2) did depend more on visual-spatial strategies than the girls, and (3) depended less on verbal strategies than the girls. The target girls: (1) outperformed the low math/science achieving girls on the mental rotation items and did not show a significant advantage over the other high math/science group, (2) depended more on visual-spatial strategies than both the other two groups of girls, and (3) depended less on verbal strategies than the low math/science girls, while showing no significant difference compared to the nonoptimal high math/science girls. Examining within-group differences, the boys preferred visual-spatial strategies, while the girls in both the nontarget groups preferred verbal ones. However, for the target girls, no within-subject strategy differences were found. The present findings support the theory that, like the boys, the target girls depend more on visual-spatial strategies than do other girls. It is possible that the target girls use a combination of visual-spatial and verbal strategies when solving mental rotation tasks.     

Body-specific representations of spatial location

The body specificity hypothesis (Casasanto, 2009) posits that the way in which people interact with the world affects their mental representation of information. For instance, right- versus left-handedness affects the mental representation of affective valence, with right-handers categorically associating good with rightward areas and bad with leftward areas, and left-handers doing the opposite. In two experiments we test whether this hypothesis can: extend to spatial memory, be measured in a continuous manner, be predicted by extent of handedness, and how the application of such a heuristic might vary as a function of informational specificity. Experiment 1 demonstrates systematic and continuous spatial location memory biases as a function of associated affective information; right-handed individuals misremembered positively- and negatively-valenced locations as further right and left, respectively, relative to their original locations. Left-handed individuals did the opposite, and in general those with stronger right- or left-handedness showed greater spatial memory biases. Experiment 2 tested whether participants would show similar effects when studying a map with high visual specificity (i.e., zoomed in); they did not. Overall we support the hypothesis that handedness affects the coding of affective information, and better specify the scope and nature of body-specific effects on spatial memory.     

Mental rotation and real-world wayfinding

Sex differences in mental rotation skills are a robust finding in small-scale laboratory-based studies of spatial cognition. There is almost no evidence in the literature, however, relating these skills to performance on spatial tasks in large-scale, real-world activities such as navigating in a new city or in the woods. This study investigates the connections between mental rotation skills as measured by the Vandenburg-Kuse Mental Rotations test and the performance of college students (n=211) navigating a 6-km orienteering course. The results indicate that mental rotation skills are significantly correlated with wayfinding performance on an orienteering task. The findings also replicate sex differences in spatial ability as found in laboratory-scale studies. However, the findings complicate the discussion of mental rotation skills and sex because women often performed as well as men despite having lower mean test scores. This suggests that mental rotation ability may not be as necessary for some women's wayfinding as it is for men's navigation.     

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.     

Dissociating the effects of angular disparity and image similarity in mental rotation and object recognition

Performance is often impaired linearly with increasing angular disparity between two objects in tasks that measure mental rotation or object recognition. But increased angular disparity is often accompanied by changes in the similarity between views of an object, confounding the impact of the two factors in these tasks. We examined separately the effects of angular disparity and image similarity on handedness (to test mental rotation) and identity (to test object recognition) judgments with 3-D novel objects. When similarity was approximately equated, an effect of angular disparity was only found for handedness but not identity judgments. With a fixed angular disparity, performance was better for similar than dissimilar image pairs in both tasks, with a larger effect for identity than handedness judgments. Our results suggest that mental rotation involves mental transformation procedures that depend on angular disparity, but that object recognition is predominately dependent on the similarity of image features.     

Are implicit affective evaluations related to mental rotation performance?

Conscious and unconscious emotions are related to mental rotation. In this study, we investigated if also unconscious emotional evaluations of the stimuli are related to mental rotation performance. 114 students (39 men, 75 women) solved implicit and explicit affective evaluations and a psychometric mental rotation test with cube and pellet figures. Furthermore, the use of spatial toys, the stereotyping of spatial abilities, and the self-rating in spatial abilities were registered. The mental rotation test with pellet figures was more difficult than the one with cube figures. Mental rotation performance was predicted by the self-rating of spatial abilities. For the cube figures, it was additionally predicted by the implicit affective evaluation of those figures. The results did not differ between men and women. The study provides evidence for a relation between affective emotional evaluations and mental imagery processes, although this does not hold true for all stimulus types.     

Handedness and calendar orientations in time-space synaesthesia

In one common variant of time-space synaesthesia, individuals report the consistent experience of months bound to a spatial arrangement, commonly described as a circle extending outside of the body. Whereas the layout of these calendars has previously been thought to be relatively random and to differ greatly between synaesthetes, Study 1 provides the first evidence suggesting one critical aspect of these calendars is mediated by handedness: clockwise versus counter-clockwise orientation. A study of 34 time-space synaesthetes revealed a strong association between handedness and the orientation of circular calendars. That is, left-handed time-space synaesthetes tended to report counter-clockwise arrangements and right-handed synaesthetes clockwise. Study 2 tested whether a similar bias was present in non-synaesthetes whose task was to memorize and recall the spatial configuration of a clockwise and counter-clockwise calendar. Non-synaesthetes' relative performance on these two sorts of calendars was significantly correlated with their handedness scores in a pattern similar to synaesthetes. Specifically, left-handed controls performed better on counter-clockwise calendars compared to clockwise, and right-handed controls on clockwise over counter-clockwise. We suggest that the implicit biases seen in controls are mediated by similar mechanisms as in synaesthesia, highlighting the graded nature of synaesthetic associations.