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.     

Sex and handedness differences in EEG measures of hemispheric specialization

EEG alpha asymmetry was studied in 90 normal adults: right-handed, left-handed, and ambidextrous, male and female. Recordings were made from homologous central, parietal, and occipital leads, referenced to vertex, while subjects engaged in writing, speaking, reading, listening to speech, singing, and block design construction. These data confirm our previous findings that alpha asymmetry is task-dependent and extend them to a broader range of tasks, subjects, and leads. Among right-handers significant differences were found between the language tasks and the musical and spatial tasks: the $\text{R}\text{L}$ alpha ratio is higher in the language tasks. In addition, significant ordering of $\text{R}\text{L}$ alpha ratios was found among the language tasks themselves: WRITE å SPEAK > READ > LISTEN. No one “verbal” task can be considered representative of all language behaviors. Task differences in asymmetry were greater at the central than at the parietal leads, and no differences were found at the occiput. Differences among the handedness groups were found in $\text{R}\text{L}$ alpha ratio in specific tasks, in the relationship among tasks, and in alpha power level. Non-right-handers showed less task-dependent asymmetry. On some measures ambidexters appear to be a distinct group, not simply representing the middle range of a left-handed/right-handed continuum. Reversal of the “expected” right-handed pattern (SPEAK $\text{R}\text{L}$ ratio > BLOCKS $\text{R}\text{L}$ ratio) was seen in 10% of right-handers, and in 36% of left-handers, particularly among left-handed females (46%), suggesting a possible sex difference among non-right-handers. No sex difference was found among right-handers on any task with any measure at any lead.     

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.     

Sex differences in mathematical reasoning ability at age 13: their status 20 years later

Reported is the 20-year follow-up of 1,975 mathematically gifted adolescents (top 1%) whose assessments at age 12 to 14 revealed robust gender differences in mathematical reasoning ability. Both sexes became exceptional achievers and perceived themselves as such; they reported uniformly high levels of degree attainment and satisfaction with both their career direction and their overall success. The earlier sex differences in mathematical reasoning ability did predict differential educational and occupational outcomes. The observed differences also appeared to be a function of sex differences in preferences for (a) inorganic versus organic disciplines and (b) a career-focused versus more-balanced life. Because profile differences in abilities and preferences are longitudinally stable, males probably will remain more represented in some disciplines, whereas females are likely to remain more represented in others. These data have policy implications for higher education and the world of work.     

Real-life spatial skills, handedness, and family history of handedness

According to , pronounced left hemisphere lateralization for language abilities in women, as in female absolute right-handers, limits their right hemisphere capacity and spatial abilities. This study examines the degree of handedness and the family history of non-right-handedness with respect to real-life spatial abilities in women. Twenty-four women had, first, to learn a new route and, second, to orient themselves within a labyrinth. In the former task, the number of errors and completion time were evaluated; in the latter task, degree of error for orienting was recorded. The results show that, contrary to Annett's prediction, right-handers with and without a family history of non-right-handedness did not differ on these measures. In addition, and unexpectedly, absolute right-handers were found to surpass non-absolute ones in the spatial orientation task. These findings do not support Annett's hypothesis and are discussed in relation to functional cerebral organization.     

Familial handedness and its relation to spatial ability following strategy instructions

This study compared subjects from right-handed families with subjects from nonrighthanded families in their ability to solve a mental-rotation task when instructed to use one of two different spatial strategies. All subjects completed a pretest Vandenberg. Next, one of the following procedures was presented prior to administering the Vandenberg posttest: Group 1 was given mental-rotation instructions, Group 2 was given spatial-orientation instructions, and Group 3 (control group) was given no special directions. For familial right-handers, no condition effects were found. In contrast, familial nonright-handers benefited significantly from mental-rotation instructions when compared both to their own control group and to familial right-handed subjects given the same instructions. However, with orientation instructions, the familial nonright-handers showed significantly less posttest improventnt than their control group. These results suggests familial non-rright-handers may be stronger in ability to use one spatial strategy, transformation of mental images, and weaker on a second, reorientation in relation to left-right cues. The educational and research implications of these findings are discussed.     

Sex differences in impulsivity and intellectual ability

Literature on sex differences in impulsivity has tended to focus on differences between groups, while ignoring relationships beyond zero order correlations. The purpose of this study was to evaluate Maccoby's hypothesis (1966) of opposite-direction correlations where the relationship between a set of variables (e.g., impulsivity and intellectual ability) is curvilinear, with males and females being systematically distributed on opposite sides of the curve. The Primary Mental Abilities (PMA) and Matching Familiar Figures tests were administered to 44 males and 49 females. The relationship between all of the PMA subtests and impulsivity was curvilinear for males, but linear for females on all but one of the subtests. The importance and implications of examining distribution differences rather than group differences are discussed.Support for this study has come from the Office of Research Administration, University of Kansas, Grant Number 3581-5038. This paper was presented in part at the meeting of the American Psychological Association, Chicago, August 1975, Division 7.     

Powers, causation, and modality

A complex theory concerning powers, natures, and causal necessity has emerged from the writings of P. H. Hare, E. H. Madden, and R. Harré. In the course of rebutting objections that other critics have raised to the power account of causation, I correct three of its genuine difficulties: its attempt to analyze power attributions in terms of conditional statements; its characterization of the relation between something's powers and its nature; and its doctrines concerning conceptual necessity. The resulting interpretation of causal modalities is then subsumed under a more general power account of modality, related at a number of points to considerations concerning powers, and further illustrating their philosophical importance.     

Agency, properties and causation

The paper argues against the very commonly held view that whenever a substance may be said to be the cause of something, a fuller and metaphysically more accurate understanding of the situation can always be obtained by looking to the properties in virtue of which that substance was able to bring about the effect in question. Paul Humphreys’ argument that when a substance is said to have produced an effect, it always turns out to be an aspect or property of that substance which brought about the effect in question is examined and criticized; it is argued that it is based on an illegitimate application of Mill’s Methods of Difference and Agreement to the case. Mill’s methods, it is suggested, are methods of empirical, not of ontological enquiry. The paper then turns to examine an argument by Mele which appears to depend on a structurally rather similar assumption that if there is nothing about a subject which could explain why she does one thing rather than another, it cannot really be up to that subject which thing occurs. It is suggested that, too, the inference is faulty, and that once it is rejected, one common objection to libertarianism—the argument from luck—might be more readily met.     

Sex differences in spatial ability and spatial activities

Explanations of sex-related differences in spatial ability emphasizing the role of sex-differentiated experience have not been supported by direct measurement of spatial activities during adolescence, the period when these differences seem to increase. The present research involved development of a scale to measure the spatial experience of adolescents and adults. In Study 1, a list, as complete as possible of adolescent activities was compiled and given to undergraduate judges for ratings of involvement of spatial skills and sex-typing. Judges also indicated whether they had participated in each activity. Activities considered spatial by 75% or more of the judges were used to develop a spatial experience questionnaire. Judgments of the spatial nature of tasks were positively correlated with judged masculinity and with greater male than female participation. In Study 2, participation in spatial activities by undergraduates was correlated with spatial ability as measured by the Differential Aptitude Test. The activity questionnaire should prove useful in studying the development of spatial ability in adolescents and adults.     

Skill, strength, handedness, and fatigue

Thirty male subjects, 20 of whom were self-classified left-handers and 10 right-handers, were tested on a grip-strength task and a handwriting task with each hand, both under normal conditions and in a situation of induced experimental fatigue. On the basis of questionnaire scores, the left-handers were sub-divided into two groups comprising the 10 most left-handed and the 10 least left-handed subjects. The test of grip strength showed a small but significant deterioration in performance of both hands from fatigue. With the handwriting task, a similar significantly adverse effect of fatigue was recorded for all groups as well as a large significant difference in performance between the preferred and nonpreferred hands under normal conditions, which decreased under fatigue. An explanation of these differential effects is discussed in terms of the greater efficiency of the preferred hand in the highly developed skill of handwriting.