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Effect of sex and hemisphericity upon corpus callosal area. Abbreviations: R-bom (right brain-oriented male), R-bof (right brainoriented female), L-bom (left brain-oriented male), and L-bof (left brainoriented female). Scale: whiskers (SD), outer box (SEM), and inner box (Mean, cm 2 ).
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Individuals differ in the number of corpus callosum (CC) nerve fibers interconnecting their cerebral hemispheres by about threefold. Early reports suggested that males had smaller CCs than females. This was often interpreted to support the concept that the male brain is more "lateralized" or "specialized," thus accounting for presumed male predomin...
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... still greater group CCA separations occurred after the subjects were sorted both by hemisphericity and sex, as shown in Fig. 1. There it may be seen that the mean CCA of right brain-oriented individuals, regardless of sex, was substantially greater than that of left-brained males or females, and vise versa. This occurred even while the much smaller sex-specific differences in CCA were retained. Thus (Table 2) the mean CCAs of the right brain-oriented males (n ...
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... Studies analysing the direction of hand preference in relation to callosal morphology can also be found in the literature (e.g., Denenberg et al., 1991;Luders et al., 2003;Moffat, Hampson, & Lee, 1998;Morton & Rafto, 2006;Nasrallah et al., 1986;Ozdikici, 2020;Westerhausen et al., 2004). Here, however, the theoretical relationship to the corpus callosum is less clear than for consistency approaches. ...
... None of the previous studies reporting direction-based handedness group comparisons of the corpus callosum (Denenberg et al., 1991;Jäncke et al., 1997;Mitchell et al., 2003;Moffat et al., 1998;Morton & Rafto, 2006;Nasrallah et al., 1986;Ozdikici, 2020;Tuncer, Hatipoglu, & Ozates, 2005) included brain size as covariate into their analyses. Conducting this analysis for the first time, we here neither for Comparisons C nor D found significant differences, whereby the found empirical effect sizes can be considered small, ranging between d = 0.07 (6 mm 2 ) and 0.08 (7 mm 2 ) in favour of the dRH/cRH as opposed to the dLH/cLH sample. ...
Originating from a series of morphometric studies conducted in the 1980s, it appears a widely held belief in cognitive neuroscience that the corpus callosum is larger in non-right handers than in right handers (RH). However, a recent meta-analysis challenges this belief by not finding significant differences in corpus callosum size between handedness groups. Yet, relying on the available published data, the meta-analysis was not able to account for a series of factors potential influencing its outcome, such as confounding effects of brain size differences and a restricted spatial resolution of previous callosal segmentation strategies. To address these remaining questions, we here analysed the midsagittal corpus callosum of N = 1057 participants from the Human Connectome Project (HCP 1200 Young Adults) to compare handedness groups based on consistency (e.g., consistent RH vs. mixed handers, MH) and direction of hand preference (e.g., RH vs. left handers). A possible relevance of brain-size differences was addressed by analysing callosal variability by both using forebrain volume (FBV) as covariate and utilising relative area (callosal area/thickness divided by FBV) as dependent variable. Callosal thickness was analysed at 100 measuring points along the structure to achieve high spatial resolution to detect subregional effects. However, neither of the conducted analyses was able to find significant handedness-related differences in callosal and the respective effect-sizes estimates were small. For example, comparing MH and consistent RH, the effect sizes for difference in callosal area were below a Cohen’s d = 0.1 (irrespective of how FBV was included), and narrow confidence intervals allowed to exclude effects above | d | = 0.2. Analysing thickness, effect sizes were below d = 0.2 with confidence intervals not extending above | d | = 0.3. In this, the possible range of population effect sizes of hand preference on callosal morphology appears well below the effects commonly reported for factors like age, sex, or brain size. Effects on cognition or behaviour accordingly can be considered small, questioning the common practise to attribute performance differences between handedness groups to differences in callosal architecture.
... positive values indicate the cRH group to have a larger corpus callosum. (Clarke, Lufkin, & Zaidel, 1993;Clarke & Zaidel, 1994;Cowell & Gurd, 2018;Cowell, Kertesz, & Denenberg, 1993;Denenberg et al., 1991;Gurd et al., 2013;Haberling et al., 2011;Haberling, Badzakova-Trajkov, & Corballis, 2012;Habib et al., 1991;Hines et al., 1992;Jancke et al., 1997;Kertesz et al., 1987;Labache et al., 2020;Luders et al., 2003;Martens et al., 2013;McDowell et al., 2016;Moffat et al., 1998;Morton & Rafto, 2006;Nasrallah et al., 1986;Ozdikici, 2020;Steinmetz et al., 1992;Tuncer, Hatipoglu, & Ozates, 2005;Van der Haegen et al., 2011;Van Essen et al., 2013;Welcome et al., 2009;Westerhausen et al., 2004;Witelson, 1985Witelson, , 1989Witelson & Goldsmith, 1991) was not certified by peer review) is the author/funder. All rights reserved. ...
Following a series of seminal studies in the 1980s, left or mixed hand preference is widely considered to be associated with a larger corpus callosum, influencing the interpretation of findings and various theories related to inter-hemispheric processing, brain lateralisation, and hand preference. Recent reviews of the literature, however, report inconsistencies in the literature and cast doubt on the existence of such an association. The aim of the present study was to systematically evaluate and meta-analytically integrate the available data on the effect of hand preference on corpus-callosum morphology. For this purpose, articles were identified via a search in PubMed and Web of Science databases. Studies reporting findings relating handedness (assessed as hand preference) and corpus-callosum morphology in healthy participants were considered eligible. On the basis of a total of k = 25 identified studies, random-effects meta-analyses were conducted considering four different group comparisons found in the literature. That is, studies comparing participants of (a) predominantly right- (dRH) and left-hand preference (dLH), (b) consistent right (cRH) and non-cRH preference, (c) cRH with mixed-hand preference (MH), and (d) cRH with consistent left-hand hand preference (cLH). For none of these meta-analyses did we find a significant effect of hand preference, and narrow confidence intervals suggest that the existence of substantial population effect sizes can be excluded. For example, considering the comparison of dRH and dLH, (summarizing k = 14 studies incorporating 1910 dRH and 646 dLH participants) the estimated mean effect size was g = 0.016 (95% confidence interval: -0.12 to 0.15). Thus, the common practice of assuming an increase in callosal connectivity based on hand preference is likely invalid.
... Recently a sixth asymmetrical brain functional element bearing upon personality has been discovered by Morton and Rafto [21,27]. It is the finding of existence of laterality within the split bilateral anterior cingulate cortex (ACC). ...
... The asymmetric sides of the ACC are separated by the midline fissure of the brain. The larger side in Areas 24 and 24' appears to contain the element producing the final output of the executive system [21,27]. The relative sizes of the two sides of the ACC vary in a seemingly idiosyncratic manner [10]. ...
... We found that the corpus callosal size was significantly greater for RPs like Robert and Ronna, than in LPs like Luke and Linda. That is, RPs Robert and Ronna have up to three times greater interhemispheric communication than LP Luke and Linda did [21]. This size difference had earlier been predicted to exist to account for the dichotic deafness of LPs [16,17]. ...
... The four biophysical assays for hemisity 1.3.1.1 The Dichotic Deafness Test (Morton, 2001(Morton, , 2002Morton & Rafto, 2006). The "Tonal and Speech Materials for Auditory Perceptual Assessment," Disc 1.0 (1992), purchased from the Long Beach Research Foundation, was used to measure minor ear deafness of 115 pseudo-randomly selected subjects during simultaneous, and 90 ms-separated, presentations of dichotic consonant-vowel syllables. ...
... No relationship was found between hemisity and handedness in 113 subjects (Morton & Rafto, 2006), or 1049 subjects (Morton, Svard, & Jensen, 2014). Left brain-oriented, right-handed individuals commonly exist, as do right brain-oriented, left-handed individuals. ...
... Individuals differ in the number of CC nerve fibers interconnecting their cerebral hemispheres by about threefold. Using quantitative MRI, we found the midline CC area of 113 subjects was significantly correlated, not with handedness or sex, but with hemisity (Figures 1 and 2) (Morton, 2006). That is, right brain-oriented individuals of either sex had significantly larger CCs than left brain-oriented persons. ...
Brain laterality refers to the asymmetric location of functional elements within the bilateral brain of animals and humans. Thus far, five lateralized functions have been recognized in humans: handedness, language ability, spatial skills, facial recognition, and emotion recognition. Recently, a sixth asymmetric functional element bearing on personality has been discovered. It is the larger side of the split bilateral anterior cingulate cortex (ACC). This appears to be the final output element of the executive system of which, by logic, there can be only one. Which side is somewhat larger varies among the general population in a seemingly idiosyncratic manner, yet with a genetic basis because true-breeding lineages exist. Here, hemisity is binary measure where a person is inherently born either right brain or left brain oriented. This is determined by nine statistically robust sets of four biophysical tests, none of which depend upon personality, and five behavioral questionnaires. Crucially these hemisity methods have been validated by the Magnetic Resonance Imaging (MRI)-based discovery that the larger side of the ACC is on the same side as one’s hemisity, making MRI the primary standard for hemisity determination ( r = 0.96). There are at least 30 measurable differences in individual characteristics and behaviors between those persons whose hemsity is on the right compared to those with it on the left. The hemisity of 2929 individuals was determined by these methods. Large groups included 1428 junior and senior high schools students both in Hawaii and Utah. There were somewhat comparable numbers present for both types of hemisity. Hemisity of individuals was found stable from infancy to old age. There was no relation between hemisity and handedness. Larger corpus callosum (CC) size of male or female subjects was larger in right brainer that in left brainers. Twin studies demonstrate that CC size is inherited. Thirty-eight percent of individuals of both sexes were right brain oriented, while 62% of individuals of both sexes were left brain oriented. In pairings, there were more than twice as many couples with opposite hemisity. Of these couples, the right brain male and females were dominant. Reproductive outcomes of these were “Like father like son, Like mother like daughter.”
... Two neuroanatomical differences between individuals of left and right hemisity subtypes have been discovered. The first was that right brainers had up to a three-fold larger corpus callosum than left brainers [19]. The second revealed that the larger side of the ventral gyrus of the anterior cingulate cortex was always on the same side as the individual's hemisity [13]. ...
... The Best Hand Test alone has also been used to investigate the mean hemisity of academic and professional populations (n = 1048; [39]. [22,23,19] Utilized the ''Tonal and Speech Materials for Auditory Perceptual Assessment", Disc 1.0 (1992), purchased from the Long Beach Research Foundation. This was used to measure minor ear deafness of 115 pseudo-randomly selected subjects during simultaneous and 90 ms-separated presentations of dichotic consonant-vowel syllables. ...
... Hemisometer results were not significantly correlated with sex [23,19], handedness [24,19], pen grasp [23,19], emotional side [22], or language laterality. Hemisometry "observer side" outcomes were somewhat correlated with previously determined midline corpus callosal cross sectional areas of these subjects (r = -0.28, ...
... This produced robust data and led to the discovery by MRI of two neuroanatomical differences between right and left brainers. First, right brainers tend to have larger corpus callosi than left brainers [41,43]. Second, the asymmetric anterior cingulate was largest on the brain side of hemisity. ...
Abstract A multiple module model of human consciousness is needed because several powerful subconscious elements have been found which strongly influence behavior. Recognition of the existence of brain-mind modules is as old as written history. Recently, McLean’s evolutionary Triune Brain model, has been expanded to Morton’s Dual Quadbrain Model of modular consciousness. The bilaterality of the cerebrum is necessary because the left hemisphere is specialized in top-down logic, which cannot occur in the same space as the right hemisphere’s bottom-up orientation. These differences have led to the concept of hemisity, which is based upon which side of the anterior cingulate, part of the executive ego, was larger, thus determining the right or left brain-orientation of the individual. The cerebellum which is also bilateral, houses Freud’s Superego with its life and social orientation, so often emulated in religion. It also houses the Thanatos, Reactive Mind, Pain Body, and mutated developmental arrest repair program (xDARP), source of conflict between mates leading to more than 50% to divorce in the US. Lastly, the brain core is also bilateral with Freud’s ferocious wolf-Id on one side and the loyal and supportive dog-Id on the other. These produce the hostile or friendly ultimate brain output. With these seven brain modules active, we are a formidable society of seven.
... Zenhausern (1978) argued that a preference to process stimuli in a visuospatial manner is related to reliance on the right-brain hemisphere, while a preference to process stimuli in a verbal manner is associated with the left brain hemisphere. Following Zenhausern's work, the hypothesis of hemispheric specialization has received mixed support, but recent research has revitalized the field (Morton, 2001(Morton, , 2002(Morton, , 2003a(Morton, -2003dMorton, 2013;Morton & Rafto, 2006, 2010. For example, Merckelbach, Muris, Horselenberg, and Jong (1997) used Zenhausern's Preference Test and electroencephalogram (EEG), and showed that those with a right hemisphere preference showed greater right brain activation in a resting state. ...
... For example, Morton and Rafto (2010) found that the anterior cingulated cortex (ACC) was thicker for a participant's preferred hemisphere. The size of the corpus callosum was also shown to be larger in individuals with a right-brain preference (Morton & Rafto, 2006). In addition to brain-based evidence of hemisphericity, hemispheric preference has also been correlated with performance on behavioral measures, such as phased mirror tracing (Morton, 2003a(Morton, , 2003b(Morton, , 2003c(Morton, , 2003d and dichotic listening tests (Morton, 2002). ...
We examined the relationship between cognitive style empathy and willingness to help. In Study 1 (N = 186) we measured preference for visuospatial or verbal cognitive style using the ZenQ (Zenhausern, 1978), and empathy using the Interpersonal Reactivity Index (Davis, 1983). In Study 2 (N = 76), we experimentally elicited verbal or visual cognitive processing via priming and measured empathy in response to a vignette about a woman injured in a car accident. In both studies, we measured willingness to help by assessing participants’ willingness to assist the injured woman. Results showed that visuospatial cognitive processing increased empathy and willingness to help. Empathic concern mediated the relationship between cognitive style and willingness to help. Results highlight the importance of mental imagery in increasing empathy and helping.
... In contrast to analog hemisphericity, the binary "hemisphericity" (hemisity) concept was more in alignment with the qualitatively different and mutually antagonistic modes of data processing of the opposite cerebral hemispheres, and certainly was much easier to quantify. Numerous "hemisphericity" reports were published (Morton, 2001(Morton, , 2002(Morton, , 2003aMorton and Rafto, 2006). This series was continued by publication of additional "hemisity" reports (Morton and Rafto, 2010;Morton, 2012;Morton et al., 2014). ...
... Two neuroanatomical differences were found. The first was the observation that the corpus callosum midline cross sectional area of RPs was up to three times larger than that of the LPs (Morton and Rafto, 2006). The implications of this discovery will be discussed later. ...
... As mentioned, the cross-sectional area of the midline of the corpus callosum (CCA) was found to be significantly smaller in LPs than in RPs, and to be unrelated to sex or handedness (Morton and Rafto, 2006). These observations, illustrated in Figure 2, have had several ramifications. ...
Three terms define brain behavioral laterality: Hemispheric dominance identifies the cerebral hemisphere producing one’s first language. Hemispheric asymmetry locates the brain side of non-language skills. A third term is needed to describe a person’s binary thinking, learning, and behaving styles. Since the 1950s split-brain studies, evidence has accumulated that individuals with right or left brain behavioral orientations (RPs or LPs) exist. Originally, hemisphericity sought, but failed, to confirm the existence of such individual differences, due to its assertion that each individual lay somewhere on a gradient between competing left and right brain extremes. Recently, hemisity, a more accurate behavioral laterality context, has emerged. It posits that one’s behavioral laterality is binary: i.e., inherently either right or left brain-oriented. This insight enabled the quantitative determination of right or left behavioral laterality of thousands of subjects. MRI scans of right and left brain-oriented groups revealed two neuroanatomical differences. The first was an asymmetry of an executive element in the anterior cingulate cortex. This provided hemisity both a rationale and a primary standard. RPs and LPs gave opposite answers to many behavioral preference either-or, forced choice questions. This showed that several sex vs. hemisity traits are being conflated by society. Such was supported by the second neuroanatomical difference between the hemisity subtypes, that RPs of either sex had up to three times larger corpus callosi than LPs. Individuals of the same hemisity but opposite sex had more personality traits in common than those of the same sex but different hemisity. Although hemisity subtypes were equally represented in the general population, the process of higher education and career choice caused substantial hemisity sorting among the professions. Hemisity appears to be a valid and promising area for quantitative research of behavioral laterality.
... Research on hemisphericity, for example, has demonstrated traitlike preferences for different cognitive modes that are associated with each of the two cerebral hemispheres, and that hemispheric preference can be reliably identified via performance on a variety of biophysical tasks (Morton, 2001(Morton, , 2002(Morton, , 2003. Moreover, hemispheric preference is related to variability in Corpus Callosum size with right brain oriented individuals having substantially larger CCs than left brain oriented individuals (Morton & Rafto, 2006). Other researchers have focused on some of the emotional concomitants of arousal asymmetry (Sutton & Davidson, 1997;Wheeler, Davidson, & Tomarken, 1993), demonstrating, for example, an association between LH activation and positive mood. ...
Prior research has demonstrated that semantic organization in the right hemisphere (RH) is more diffuse and specialized for distant semantic associates than is semantic organization in the left hemisphere (LH). The present research explored individual differences in this regard. If the RH is more specialized for distant semantic associates, then individuals with a more active RH should display greater activation of distant semantic associations. Two experiments were conducted to examine this issue. In both studies a line bisection task was used to assess arousal asymmetry. In Experiment 1, greater RH activation was associated with the ability to generate remote associates to three word stimuli. In Experiment 2, relatively greater RH activation was associated with enhanced priming of distant semantic associates. Taken together, these experiments demonstrate that arousal asymmetry is an individual difference variable that is related to variability in semantic organization and retrieval.
... These issues have been further resolved by the development of independent biophysical measures of hemisity, using nonverbal hand, eye, or ear-dependent measurements (Morton, 2001(Morton, , 2002(Morton, , 2003a(Morton, , 2003b. This advance led to the discovery of two different brain structural differences (the thickness of the corpus callosum and the asymmetry of the anterior cingulate) between right brain-and left brain-oriented individuals and to the proposal of a unilateral executive element (Morton & Rafto, 2006, 2010. Hemisity is shown to influence the manifestation of behavioral preferences as evidenced by the high correlation between the hemisity questionnaires (Morton, 2002(Morton, , 2003c(Morton, , 2012a and the biophysical methods (Morton, 2001(Morton, , 2002(Morton, , 2003a(Morton, , 2003b and MRI hemisity results (Morton & Rafto, 2006, 2010. ...
... This advance led to the discovery of two different brain structural differences (the thickness of the corpus callosum and the asymmetry of the anterior cingulate) between right brain-and left brain-oriented individuals and to the proposal of a unilateral executive element (Morton & Rafto, 2006, 2010. Hemisity is shown to influence the manifestation of behavioral preferences as evidenced by the high correlation between the hemisity questionnaires (Morton, 2002(Morton, , 2003c(Morton, , 2012a and the biophysical methods (Morton, 2001(Morton, , 2002(Morton, , 2003a(Morton, , 2003b and MRI hemisity results (Morton & Rafto, 2006, 2010. We hypothesized from this that these preferences would significantly influence the selection of one's college and/or professional track. ...
... Perhaps it was not surprising that university science librarians, people skilled in the assessment of details, tended to be enriched in LPs (73%) and only 4 of the 15 (27%) were RPs. It is predicted that corpus callosal size will be lower than average among LP librarian groups because LPs have been found to have significantly smaller corpus callosal cross-sectional areas than RPs (Morton & Rafto, 2006). ...
Hemisity refers to binary thinking and behavioral style differences between right and left brain-oriented individuals. The inevitability of hemisity became clear when it was discovered by magnetic resonance imaging (MRI) that an anatomical element of the executive system was unilaterally embedded in either the right or the left side of the ventral gyrus of the anterior cingulate cortex in an idiosyncratic manner that was congruent with an individual’s inherent hemisity subtype. Based upon the MRI-calibrated hemisity of many individuals, a set of earlier biophysical and questionnaire hemisity assays was calibrated for accuracy and found appropriate for use in the investigation of the hemisity of individuals and groups. It had been reported that a partial sorting of individuals into hemisity right and left brain-oriented subgroups occurred during the process of higher education and professional development. Here, these results were extended by comparison of the hemisity of a putative unsorted population of 1,049 high school upper classmen, with that of 228 university freshmen. These hemisity outcomes were further compared with that of 15 university librarians, here found to be predominantly left brain-oriented, and 91 academically trained musicians, including 47 professional pianists, here found to be mostly right brainers. The results further supported the existence of substantial hemisity selection occurring during the process of higher education and in professional development.
