M.P. Bryden

Magnitude of sex differences in spatial abilities: a meta-analysis and consideration of critical variables.

In recent years, the magnitude, consistency, and stability across time of cognitive sex differences have been questioned. The present study examined these issues in the context of spatial abilities. A meta-analysis of 286 effect sizes from a variety of spatial ability measures was conducted. Effect sizes were partitioned by the specific test used and by a number of variables related to the experimental procedure in order to achieve homogeneity. Results showed that sex differences are significant in several tests but that some intertest differences exist. Partial support was found for the notion that the magnitude of sex differences has decreased in recent years. Finally, it was found that the age of emergence of sex differences depends on the test used. Results are discussed with regard to their implications for the study of sex differences in spatial abilities.

Gender, level of spatial ability, and lateralization of mental rotation ☆

The present study indicates that some of the inconsistencies in studies of the lateralization of mental rotation may be a consequence of uncontrolled individual differences in the general level of spatial ability. In order to investigate the relation between spatial ability and the lateralization of mental rotation, 48 subjects (24 males and 24 females) were divided into three groups based on their performance on a standardized test of spatial ability. They then performed a lateralized two-dimensional mental rotation task. The results showed the typical mental rotation function in that angle of rotation and reaction time were linearly related. A significant spatial ability by visual field interaction indicated that subjects with low spatial ability had a left field advantage, whereas subjects with medium spatial ability showed no field advantage and subjects with high spatial ability showed a right field advantage. Gender also interacted with visual field, with males showing a left visual superiority and females an insignificant right visual field advantage. A significant three-way interaction of gender, spatial ability, and angle of rotation reflected the fact that low spatial males were more profoundly affected by rotation than the other groups. The results suggest that at least some of the inconsistent findings in studies of lateralization of mental rotation may be accounted for by differences in the level of spatial ability.

The corpus callosum and cerebral speech lateralization

In order to specify the callosal involvement in the establishment of cerebral lateralization, a dichotic listening task was administered to six subjects with congenital absence of the corpus callosum, two callosotomized patients, and two hemispherectomized patients. The acallosal subjects were also compared to six subjects matched for age, sex, and hand dominance as well as to six subjects also matched for IQ. Our findings indicate that language functions, as assessed by dichotic listening performance, are more strongly lateralized in callosal agenesis subjects than in IQ-matched normal controls. Our results also reveal that hemispherectomized patients typically show a strong ear-advantage favoring the ear contralateral to their remaining hemisphere. Callosotomized patients, on the other hand, show a more variable pattern of results that seems to be related to the postsurgical time interval. Finally, our findings suggest that there might be a relationship between IQ and lateralization in subjects with borderline or mild deficiency.

A comparison of hand preference in Japan and Canada.

Abstract An analysis was performed on 47 items of a hand preference inventory administered to 1275 undergraduate students in Japan and Canada. Factor analysis indicated that items grouped into three factors, representing skilled activities, unskilled activities, and turning movements. Analysis of the factor scores revealed that neither skilled handedness nor unskilled handedness was significantly influenced by cultural group or sex. On the third factor, Japanese students were far more right - handed than were Canadian students. Although mean factor scores for skilled handedness did not differ between groups, the prevalence of left - handedness was significantly lower in Japan than in Canada. Cultural pressures have their primary effect on turning movements, and on specific skilled activities such as writing and eating. Although the data are consistent with the view that a right shift for skilled activities has been superimposed on an undifferentiated handedness, other considerations make such a theory less tenable. The majority of people in the world are right - handed, and right - handedness has often been used as a marker for normal brain lateralization. It is generally agreed that some aspects of handedness, such as the hand used for writing (Beukelaar & Kroonenberg, 1986), can be influenced by pressures from parents or teachers. Furthermore, much of the lore indicates that the prevalence of handedness is lower in Oriental societies than in Caucasian ones. Thus, Porac, Rees, and Buller (1990), in a review of handedness studies, indicate that the prevalence of left - handedness is 4.6% in Orientals and 8.7% in Caucasians. In studies of Japanese populations, Hatta and Nakatsuka (1976) give an incidence of 3% in adults, while Rymar, Kameyama, Niwa, Hiramatsu, and Saitoh (1984) give an incidence of 3.7% and Shimizu and Endo (1983) one of 3.2% in children. Similarly, Teng, Lee, Yang, and Chang (1979) give a value of 5.0% in Taiwan, and Hardyck, Goldman, and Petrinovitch (1975) one of 6.5% among children of Oriental descent living in California. In a large - scale study of Japanese school children, Komai and Fukuoka (1934) noted that whereas the incidence of left - handed writing and eating dropped to a very low value through the primary grades, 6% of girls and 9% of boys continued to use the left hand for some activities as late as Grade 8. The very low incidences of left - handedness reported in some of the other Japanese studies may therefore be the consequence of an emphasis on writing hand, although it should be noted that writing hand was not included in the Hatta and Nakatsuka (1976) inventory. Furthermore, a formal meta - analysis of the literature on human handedness by Seddon and McManus (1993), incorporating more studies than those cited by Porac et al. (1990), suggests that there are no compelling cultural differences in handedness. There are several problems with the existing data concerning the prevalence of left - handedness in different cultures. In many cases, classification of handedness is based solely on writing hand, and educational systems may vary in the degree to which they discourage left - handed writing (cf. Beukelaar & Kroonenberg, 1986). In other cases, the contrast is between performance on one questionnaire in one society and that on another quite different questionnaire in another society. Differences in the selection of items may therefore lead to differences in the reported incidence of left - handedness. The largest cross - cultural study of which we are aware, that of Perelle and Ehrman (1994), employed a 12 - item questionnaire, but reported cross - cultural data only on writing hand and on self - perceived handedness. Furthermore, there are no Oriental data in that study, and only one sample that is not predominantly Caucasian (that from Nigeria). However, the fact that the self - perceived prevalence of left - handedness varies from a low of 4. …

Locus of information in words and the right visual field effect

The right visual field (RVF) advantage found for the identification or classification of words has usually been interpreted as evidence for left hemisphere language functions. It has more recently been explained as the result of the fact that the most informative part of the word, presumably the beginning, is in a region of better visual acuity. It is not clear from existing evidence that the beginnings of words are in fact more informative. The present study assessed the locus of information in words by deleting either the initial or terminal one or two letters. Subjects were required to generate a completion. Regardless of whether subjects were scored as correct for generating the original target word (as would be appropriate in a naming study) or for producing any legitimate word (as would be appropriate for a lexical decision study), the results indicated that most words have more information in the initial letters. Nevertheless, there are exceptions to this rule, and some words have more terminal information. Equal numbers of words with more initial information and with more terminal information were selected for two visual field studies in order to assess the effect of the locus of information on visual laterality. In neither a lexical decision study nor a naming study did locus of information affect the commonly observed right visual field superiority. Thus the distribution of information is not likely to be a major confounding variable in laterality studies employing horizontally presented words.

Toward a model of dichotic listening performance

Dichotic listening performance for different classes of speech sounds was examined under conditions of controlled attention. Consideration of the complex of target item and competing item demonstrated that, in general, targets were more accurately identified when the competing item shared no relevant features with it and less accurately identified when the competing item shared place, voice, or manner with the target item. Nasals as well as stops demonstrated a significant right-ear advantage (REA). False alarm rates were very similar for left and right attentional conditions, whereas intrusions from the right ear while attending to the left were far more common than intrusions from the left while attending to the right. Attention is viewed as serving to select the stimuli that will be reported, but at a late stage, and only after the right ear perceptual advantage has had its effect. A model of dichotic listening performance is proposed in which both the ease of localizing the item and the strength of evidence for the presence of the item are relevant factors.

On the possible dangers of using horizontal word displays in visual field studies.

In a sample of 100 four-letter words, there was more information about the identity of the words in the first letter than in the last letter. However, information asymmetry did not correlate with visual field differences in a lexical decision study. It therefore may be possible to use horizontally displayed short words in visual field studies without being concerned about peripheral factors. Different factors affect the recognition of vertical and horizontal displays, and the use of vertical displays is not advised.

Handedness in Mental Retardation

Mentally retarded and age-matched normal controls with no history of parental sinistrality were examined for their handedness with the Waterloo Handedness Questionnaire (Singh & Bryden, 1994). Normal controls showed a clear rightward bias, with the effect being significantly higher for skilled as compared to unskilled hand items. Mentally retarded subjects showed mixed handedness with a nonsignificant difference in performance between skilled and unskilled hand items.

Expectancy effects: cost-benefit analysis of monaurally and dichotically presented speech.

In three experiments, cost-benefit analysis was used to determine the role of attention in the processing of auditory information. In two experiments consonant-vowel syllables were presented monaurally, while in the third the mode of presentation was dichotic. For all three experiments the ability to detect a target stimulus under conditions in which precued location information was valid or invalid was contrasted with detection in a neutral condition where no location information was provided. The results indicated that attention can be effectively deployed under monaural conditions when either a simple detection or a discriminative response is required. Similar conclusions cannot be reached when considering the effectiveness of attention under conditions of dichotic listening. These results are discussed in relation to accounts which argue that dichotic listening performance is critically dependent upon auditory disembedding and where attention is viewed as a late process involving response selection.

Rolling the dice: a comment on Klein and McInnes "Visual field differences in the processing of numerical stimuli".

Interest in the nature of right hemisphere language processing in intact subjects’ has burgeoned following Sperry and Gazzaniga’s seminal work with a small number of split-brain patients (see Patterson & Besner, 1984 for a review). Frequently, research on this topic has involved the tachistoscopic presentation of two or more different types of material in the left and right visual fields, with the goal of showing that visual field effects are dependent on the type of material. The common inference is that left visual field (LVF) superiorities or reduced right visual (RVF) superiorities are indicative of an increased involvement of the right hemisphere. Thus, for example, there have been many attempts to show that concrete words show a smaller RVF effect than abstract words (e.g., Boles, 1983; Day, 1977, 1979; Hines, 1977; Lambert & Beaumont, 1983; McMullen & Bryden, 1987). When such an effect is found, it is suggested that the right hemisphere is more involved with the processing of concrete words than with abstract words. Another popular argument is that ideographic scripts do not allow for phonological processing, and therefore can be processed by both left and right hemispheres (but more efficiently in the right hemisphere), whereas alphabetic and syllabic scripts allow for phonological processing, and