Fluctuating asymmetry and psychometric intelligence

The impact of developmental instability on Voxel-Based Morphometry analyses of neuroanatomical abnormalities in schizophrenia

The etiologic factors underlying schizophrenia have been conceptualized as reflecting two largely genetic components - those unique to schizophrenia and those representing vulnerability to neurodevelopmental deviation in general. The Developmental Instability (DI) approach suggests that the latter can be indexed by minor physical anomalies (MPAs), which assess early prenatal growth abnormalities, and fluctuating anatomic asymmetries (FA), which reflects later deviations. Individuals with schizophrenia (N=19) had elevated scores on both measures as compared to healthy controls (N=23). Further, MPAs and FA were very highly correlated in the sample of individuals with schizophrenia but not in controls. In order to identify neuroanatomic variation linked with the unique factor, we conducted gray matter Voxel Based Morphometry analyses of group membership, with and without treating a composite measure of DI (based on FA, and MPAs) as a covariate. When DI was treated as a covariate, many more gray matter regions were found to statistically differ as a function of diagnosis. These results support the DI approach and suggest that the unique etiologic factors associated with schizophrenia lead to widespread gray matter volume reductions.

Whole brain size and general mental ability: a review

We review the literature on the relation between whole brain size and general mental ability (GMA) both within and between species. Among humans, in 28 samples using brain imaging techniques, the mean brain size/GMA correlation is 0.40 (N = 1,389; p < 10⁻¹⁰); in 59 samples using external head size measures it is 0.20 (N = 63,405; p < 10⁻¹⁰). In 6 samples using the method of correlated vectors to distill g, the general factor of mental ability, the mean r is 0.63. We also describe the brain size/GMA correlations with age, socioeconomic position, sex, and ancestral population groups, which also provide information about brain–behavior relationships. Finally, we examine brain size and mental ability from an evolutionary and behavior genetic perspective.

Developmental Instability and Markers of Schizotypy in University Students

Fluctuating asymmetries (FA) and minor physical anomalies (MPAs) are markers of developmental instability (DI), an index of the degree to which an organism was subject to genomic or environmental stress during development. Measures of DI are characteristic of schizophrenia and are thought to reflect an underlying genetic liability for schizophrenia spectrum disorders. Whereas MPAs reflect developmental stress relatively early in the first trimester in utero, skeletal FAs reflect developmental stress throughout the lifespan. Both measures were collected to provide some indication of the associated developmental time course. In addition to DI measures, several psychometric measures of schizotypy were administered in a sample of university students ( n = 81). It was hypothesized that increased DI may relate to schizotypal symptoms in a group of healthy undergraduate students. Schizotypy scores were positively correlated with FA, but not MPAs. This finding suggests that DI, as indexed by FA, is important for normal range variation in schizotypal characteristics, just as it is important for normal range variation in intelligence. Second, considered in the context of studies demonstrating that schizophrenia is associated with elevated MPAs, these results suggest that developmental stress likely occurs earlier in development for schizophrenia than schizotypy.

Fluctuating Asymmetry and Individual Variation in Regional Gray and White Matter Volumes: A Voxel-Based Morphometry Study

Composite measures of fluctuating asymmetry (FA) of skeletal features are commonly used to estimate developmental instability (DI), the imprecise expression of developmental design due to perturbations during an individual's growth and maturation. Though many studies have detailed important behavioral correlates of FA, very little is known about its possible neuroanatomical correlates. In this study we obtained structural brain MRI scans from 20 adults and utilized voxel-based morphometry (VBM) to identify specific regions linked to FA. Greater FA predicted greater whole brain white matter volume, and a trend in the same direction was noted for whole brain gray matter volume. Greater FA was associated with significantly greater gray and white matter volumes in discrete brain regions, most prominently in the frontal lobes and in the right cerebral hemisphere. Developmental studies are needed to identify when FA-related brain differences emerge and to elucidate the specific neurobiological mechanisms leading to these differences.

Morphology and Behavior: Phrenology Revisited

Research conducted by evolutionary psychologists and biologists shows that subtle individual differences in body morphology can be related to surprising and important differences in human behavior and reproductive success. The authors summarize recent work on these effects as they relate to fluctuating asymmetry, facial attractiveness, finger digit morphology, sexually dimorphic differences in body configuration, and head circumference. Examples include the discovery that women who have sex with bilaterally symmetrical men report more orgasms; men with attractive faces have higher quality sperm; the length of the index finger in relation to the ring finger is related to verbal fluency, spatial ability, and the risk of autism; women with an hourglass figure have more regular menstrual cycles and are more fertile; and the sound of a person's voice predicts his or her sexual behavior.

Sexual orientation and fluctuating asymmetry in men and women

Previous research suggests that individuals' sexual orientation may be affected by developmental instability (DI) induced by exposure to prenatal stresses. We tested this relationship using fluctuating asymmetry (FA), the small random deviations from symmetry that arise in otherwise bilaterally symmetrical traits as a consequence of developmental noise and developmental instability. Differences among individuals reflect variation in their exposure to and ability to accommodate for stresses experienced during development as well as to developmental noise that arises due to cellular stocasticity. FA measurements for 156 heterosexual and 132 homosexual men and women participants provided strong support for the developmental instability hypothesis: FA was significantly higher in both male and female homosexuals (men: four of seven bilateral traits and composite FA values (cFA); women: five of seven bilateral traits and composite FA values). Although finger-length ratios (FLRs), an indirect marker for prenatal hormones, were sex-atypical (e.g., feminized) for homosexual men, we failed to detect any relationship between FA levels and 2D:4D finger-length ratios (FLRs). Hence, although elevated levels of developmental stress appear to be linked to shifts in sexual orientation, the underlying mechanism does not seem to be connected to sex-atypical prenatal hormones. Additional analyses with sex atypical individuals are needed to confirm this.

Spearman's Law of Diminishing Returns in Normative Samples for the WISC-IV and WAIS-III

In order to explain observed variations in intelligence test scores, Spearman (1927 ) proposed the “law of diminishing returns” (SLODR). It states that the g saturation of cognitive ability tests decreases as a function of ability or age. Published studies have shown mixed results. However, a recent review ( Hartmann & Nyborg, 2004 ) suggests that there is evidence for differences in g saturation by ability level, but that observed age effects on g saturation are most likely to be a consequence of the ability effect. The current study analyzed the standardization data of the most recent Wechsler scales for both children and adults from several different countries. This study did not find evidence to support either the ability or age version of SLODR by using large normative samples for the WISC-IV from the United States, Canada, and Australia, and for the WAIS-III from the same three countries and also from The Netherlands.

Non-verbal IQ is correlated with visual field advantages for short duration coherent motion detection in deaf signers with varied ASL exposure and etiologies of deafness

Studies have reported a right visual field (RVF) advantage for coherent motion detection by deaf and hearing signers but not non-signers. Yet two studies [Bosworth R. G., & Dobkins, K. R. (2002). Visual field asymmetries for motion processing in deaf and hearing signers. Brain and Cognition, 49, 170-181; Samar, V. J., & Parasnis, I. (2005). Dorsal stream deficits suggest hidden dyslexia among deaf poor readers: Correlated evidence from reduced perceptual speed and elevated coherent motion detection thresholds. Brain and Cognition, 58, 300-311.] reported a small, non-significant RVF advantage for deaf signers when short duration motion stimuli were used (200-250 ms). Samar and Parasnis (2005) reported that this small RVF advantage became significant when non-verbal IQ was statistically controlled. This paper presents extended analyses of the correlation between non-verbal IQ and visual field asymmetries in the data set of Samar and Parasnis (2005). We speculate that this correlation might plausibly be driven by individual differences either in age of acquisition of American Sign Language (ASL) or in the degree of neurodevelopmental insult associated with various etiologies of deafness. Limited additional analyses are presented that indicate a need for further research on the cause of this apparent IQ-laterality relationship. Some potential implications of this relationship for lateralization studies of deaf signers are discussed. Controlling non-verbal IQ may improve the reliability of short duration coherent motion tasks to detect adaptive dorsal stream lateralization due to exposure to ASL in deaf research participants.

Premorbid (early life) IQ and later mortality risk: systematic review

PURPOSE

Studies of middle-aged and particularly older-aged adults found that those with higher scores on tests of IQ (cognitive function) had lower rates of later mortality. Interpretation of such findings potentially is hampered by the problem of reverse causality: such somatic diseases as diabetes or hypertension, common in older adults, can decrease cognitive function. Studies that provide extended follow-up of the health experience of individuals who had their (premorbid) IQ assessed in childhood and/or early adulthood minimize this concern. The purpose of the present report is to systematically locate, evaluate, and interpret the findings of all such studies.

METHODS

We systematically identified individual-level studies linking premorbid IQ with later mortality by using four approaches: search of electronic databases (MEDLINE, EMBASE, and PSYCHINFO); scrutiny of the reference sections of identified reports; search of our own files; and contact with researchers in the field. Study quality was assessed by using predefined criteria.

RESULTS

Nine cohort studies met the inclusion criteria. Overall, study quality was moderate. All reports showed an inverse IQ-mortality relation; i.e., higher IQ scores were associated with decreased mortality risk. The nature of this relation (i.e., dose-response or threshold) and whether it differs by sex was unclear. The IQ-mortality association did not appear to be explained by reverse causality or selection bias. Confounding by other early-life factors also did not seem to explain the association, although some studies were not well characterized in this regard. Adult socioeconomic position appeared to mediate the IQ-mortality association in some studies, but this was not a universal finding.

CONCLUSIONS

In all studies, higher IQ in the first two decades of life was related to lower rates of total mortality in middle to late adulthood. Some plausible mechanistic pathways exist, but further examination is required. The precise nature of the IQ-mortality relation (particularly in ethnic minorities and women) and the link between IQ and disease-specific outcomes also warrants further research.

Developmental instability and the neural dynamics of the speed–intelligence relationship

Two of the most securely established findings in the biology of intelligence are the relationship between reaction time (RT) and intelligence, and the heritability of intelligence. To investigate why RT may related to intelligence, researchers have used a variety of techniques to subdivide RT into cognitive and motor components. In the current study, magnetoencephalographic (MEG) dipole latencies were used to examine the speed and timing of specific brain processing stages engaged during visually cued simple and choice reaction time tasks. Simple and choice reaction time and timing of MEG sources were considered in relation to fluid intelligence (as measured by the Raven's Advanced Progressive Matrices, RAPM). To address heritability of intelligence, developmental instability (DI) was assessed, measured here as fluctuating asymmetry. DI represents the degree to which an organism is susceptible to developmental stress arising from both environmental and genomic sources. Analyses showed that choice, but not simple reaction time was negatively correlated with RAPM score. MEG revealed a set of complex relationships between the timing of regional brain activations and psychometric intelligence. The neural component associated with integration of sensory and motor information was most associated with RAPM compared to other components. Higher values of fluctuating asymmetry predicted reduced psychometric intelligence, a result suggesting that some part of the variance of the heritability of intelligence reflects DI. Fluctuating asymmetry was significantly and negatively correlated with timing during all components of task completion. These observations suggest that fluid intelligence is primarily related to speed during processing associated with decision time, while fluctuating asymmetry predicted slower processing across all stages of information processing.

Individual olfactory signatures in common marmosets (Callithrix jacchus)

Individual discrimination is likely a prerequisite for most primate social interactions. Olfactory cues are one set of stimuli used by primates to discriminate between individuals. Despite the importance of these olfactory signatures, there is little published research assessing the existence or function of individually unique odors among primates. This review systematically assesses behavioral and biochemical aspects of individual odors in a New World primate, the common marmoset (Callithrix jacchus). There are three objectives to this review: First, behavioral evidence for odors unique to the individual is evaluated in the context of results demonstrating that marmosets are able to discriminate between the scents from a familiar and a novel individual conspecific in behavioral bioassays under a variety of conditions. Second, biochemical evidence for individual scent signatures is debated with reference to studies examining qualitative and quantitative differences between the chemical compositions of scent-mark pools from adult females. A combined gas chromatography (GC) and mass spectrometry (MS) analysis demonstrated that each female had a unique ratio of highly volatile chemicals in the scent mark that could affect individual discrimination. Finally, the possible adaptive significance of individual odors in marmosets is debated. Individual odors may play a key role in regulating both female intrasexual competition and intersexual communication by providing a basis for the assessment of individual quality.

Women's sexual interests across the ovulatory cycle depend on primary partner developmental instability

Normally ovulating women have been found to report greater sexual attraction to men other than their own partners when near ovulation relative to the luteal phase. One interpretation is that women possess adaptations to be attracted to men possessing (ancestral) markers of genetic fitness when near ovulation, which implies that women's interests should depend on qualities of her partner. In a sample of 54 couples, we found that women whose partners had high developmental instability (high fluctuating asymmetry) had greater attraction to men other than their partners, and less attraction to their own partners, when fertile.

The Pittsburgh Oral-Facial Cleft study: expanding the cleft phenotype. Background and justification

The Pittsburgh Oral-Facial Cleft study was begun in 1993 with the primary goal of identifying genes involved in nonsyndromic orofacial clefts in a variety of populations worldwide. Based on the results from a number of pilot studies and preliminary genetic analyses, a new research focus was added to the Pittsburgh Oral-Facial Cleft study in 1999: to elucidate the role that associated phenotypic features play in the familial transmission patterns of orofacial clefts in order to expand the definition of the nonsyndromic cleft phenotype. The purpose of this paper is to provide a comprehensive review of phenotypic features associated with nonsyndromic orofacial clefts. These features include fluctuating and directional asymmetry, non-right-handedness, dermatoglyphic patterns, craniofacial morphology, orbicularis oris muscle defects, dental anomalies, structural brain and vertebral anomalies, minor physical anomalies, and velopharyngeal incompetence.

HUMAN RIGHTS, BIOMEDICAL SCIENCE, AND INFECTIOUS DISEASES AMONG SOUTH AMERICAN INDIGENOUS GROUPS

Despite the efforts of international health agencies to reduce global health inequalities, indigenous populations around the world remain largely unaffected by such initiatives. This chapter reviews the biomedical literature indexed by the PubMed database published between 1963 and 2003 on South American indigenous populations, a total of 1864 studies that include 63,563 study participants. Some language family groupings are better represented than are others, and lowland groups are better represented than are highland groups. Very few studies focus on major health threats (e.g., tuberculosis, influenza), public health interventions, or mestizo-indigenous epidemiological comparisons. The prevalence rates of three frequently studied infections—parasitism, human T-cell lymphotropic viral infection (HTLV), and hepatitis—are extraordinarily high, but these facts have been overlooked by national and international health agencies. This review underscores the urgent need for interventions based on known disease prevalence rates to reduce the burden of infectious diseases in indigenous communities.

Intraobserver error associated with measurements of the hand

Measurements of the hand are common in studies that use anthropometric data. However, despite widespread usage, relatively few studies have formally assessed the degree of measurement error associated with standard measurements of the hand. This is significant because high amounts of measurement error can invalidate statistical results. In this paper, intraobserver precision estimates for measures of total hand length and total 3rd-digit length were evaluated from repeated measures on 90 subjects (180 separate hands and fingers). From this replicate data, three precision estimates were calculated: the technical error of measurement (TEM), the relative technical error of measurement (rTEM), and the coefficient of reliability (R). For both measurements, all three estimates yielded a very high degree of precision (TEM < 2 mm, rTEM < 1%, and R > or = 0.95). These results suggest that both total hand length and 3rd-digit length are sufficiently precise for anthropometric research applications.

Fluctuating asymmetry, second to fourth finger length ratios and human sexual orientation

Sexual orientation in humans may be influenced by levels of prenatal sex steroids which canalise neurodevelopment along sex-typical (heterosexual) or sex-atypical (homosexual) lines. Some evidence for sexual-orientation-related differences in putative somatic markers of prenatal sex hormones supports this view. A competing theory asserts that human homosexuality is due to developmental instability (DI) because it represents a shift from the species-typical pattern of heterosexual orientation. Evidence for elevated rates of non-right handedness among homosexuals provides limited support for this account. The current study tested both theories by examining nine bilateral somatic traits in 120 healthy heterosexual and homosexual men and women in order to compute second to fourth finger length ratios (2D:4D), a measure ascribed to levels of prenatal sex steroids, and fluctuating asymmetry (FA), a measure of DI. Homosexual men and women had significantly lower right hand 2D:4D ratios (even after controlling for handedness, height and weight differences) in comparison to heterosexuals, but sexual orientation did not relate to composite FA scores. The findings constrain the number of possible neurodevelopmental pathways responsible for sexual orientation in humans.

Fluctuating asymmetry and the human brain

Adaptive development requires the organism to resist genetic and environmental stresses that disrupt the genetic plan for growth, a buffering capacity termed developmental stability. Developmental instability is revealed by fluctuating asymmetry (FA), which has been demonstrated in many species to reflect phenotypic and genetic quality. We report (1) that a measure of developmental instability based on body FA predicts deviation from typical brain asymmetry, (2) that a combined measure of atypical brain asymmetry and body FA correlated negatively with the area of the corpus callosum, especially the portion connecting the left and right planum temporale, and (3) that this combined measure also predicted atypical asymmetry of the size of the somatosensory representation of the two hands, as determined from magnetic source imaging.

Are genes of human intelligence related to the metabolism of thyroid and steroids hormones? – Endocrine changes may explain human evolution and higher intelligence

We propose the hypothesis that genes of human intelligence are related with metabolism of thyroid and steroids hormones, which have a crucial role in brain development and function. First, there is evidence to support the idea that during hominid evolution small genetic differences were related with significant endocrine changes in thyroid and steroids hormones. Second, these neuroactive hormones are also related with unique features of human evolution such as body and brain size increase, penis and breast enlargement, pelvic sexual dimorphism, active sexuality, relative lack of hair and higher longevity. Besides underling many of the differences between humans and great apes, steroids hormones promote brain growth and development, are important in the myelination process, explain sexual dimorphisms in brain and intelligence and improve specific cognitive abilities in humans. Supporting our hypothesis, recent studies indicate differences in neuroactive hormones metabolism between humans and non-human primates. Furthermore, a link between X chromosome genes and sex steroids may explain why the frequency of genes affecting intelligence is so high on the X chromosome. This association suggests that, during hominid evolution, there was a positive feedback in both sexes on the same genes responsible for secondary sexual character development and intelligence. This interaction leads to acceleration of development of human brain and intelligence. Finally, we propose that neuroactive hormone therapy may provide significant improvement in some cognitive deficits in all stages of human life and in cases of neurodegenerative diseases. However, further investigation is needed, mainly in the enzymatic machinery, in order to understand the direct role of these hormones in intelligence.

Evolution of human mate choice

This article provides a review of evolutionary theory and empirical research on mate choices in nonhuman species and uses it as a frame for understanding the how and why of human mate choices. The basic principle is that the preferred mate choices and attendant social cognitions and behaviors of both women and men, and those of other species, have evolved to focus on and exploit the reproductive potential and reproductive investment of members of the opposite sex. Reproductive potential is defined as the genetic, material, and/or social resources an individual can invest in offspring, and reproductive investment is the actual use of these resources to enhance the physical and social well- being of offspring. Similarities and differences in the mate preferences and choices of women and men are reviewed and can be understood in terms of similarities and differences in the form of reproductive potential that women and men have to offer and their tendency to use this potential for the well-being of children.

Developmental Instability Is Associated With Neurocognitive Performance in Heterosexual and Homosexual Men, but Not in Women

Little is known about the neurodevelopmental nature of human cognitive abilities. This investigation presents evidence consistent with a hypothesis that interindividual and within-sex cognitive variations are associated with vulnerabilities to environmental sources of developmental stress. A large sample of healthy heterosexual and homosexual men and women (N=240) completed a series of visuospatial and verbal tests. A composite fluctuating asymmetry (FA) measure was computed from the lengths of the finger digits. In heterosexual men, higher FA scores were associated with poorer line orientation judgment; and in homosexual men, with poorer verbal fluency and perceptual speed. No associations were found in heterosexual or homosexual women. These results suggest that developmental instability is linked to neurocognitive integrity in men, but not in women.

Growth and developmental instability

Developmental stability reflects the ability of an individual to develop a regular phenotype under given environmental and genetic conditions. Measures of developmental instability include the degree of fluctuating asymmetry and the frequency of phenodeviants. Endocrine, neural and circulatory mechanisms that control similar development of morphological characters on the two sides of the body are also involved in controlling overall development. Cross-validation studies have shown that measures of developmental instability are positively correlated with other measures of welfare such as tonic immobility in poultry. Asymmetric animals grow less rapidly than symmetric individuals. Eleven studies have investigated the relationship between growth rate and developmental instability, and the observed effect size (Pearson correlation coefficient adjusted for sample size) is -0.15. Studies of chickens have shown that asymmetry increases as a response to selection for increased growth rate. As conditions for rearing deteriorate by higher density, fluctuating asymmetry increases and growth rate decreases, both within and among farms. Fluctuating asymmetry can be considered a measure of animal welfare since larger values reflect worse environmental conditions as experienced by the individual animal itself. Since growth rate and fluctuating asymmetry are negatively correlated, we can infer that improvement of rearing conditions leading to reduced asymmetry will both benefit the producer (in terms of increased growth), but also the animals in terms of better conditions for rearing.

Fluctuating asymmetry--indicator of what?

In a population the optimal phenotype is promoted by buffering mechanisms that keep inter- and intra-individual variation low. A link exists between canalization, that controls phenotypic variation, and developmental stability, mostly measured as fluctuating asymmetry of bilateral traits (FA). Both types of variation are associated with the functional importance of a trait, and both are increased by stress of various kinds. But there are also several instances of non-congruence. The concept of developmental stability has been found elusive, and low FA is not the unambiguous measure of well being and good genes that has been claimed. It can be concluded that developmental stability is partly governed by specific, as yet unknown, molecular processes.

Genetic factors and neurocognitive traits

Genetic contributions to phenotypic variation in general intelligence have been studied extensively. Less research has been conducted on genetic contributions to specific cognitive abilities, such as attention, memory, working memory, language, and motor functions. However, the existing data indicate a significant role of genetic factors in these abilities. Stages of information processing, such as sensory gating, early sensory registration, and cognitive analysis, also show evidence of genetic contributions. Recent molecular studies have begun to identify candidate genes for specific cognitive functions. Future research, identifying endophenotypes based on cognitive profiles of neuropsychiatric disorders, may also assist in the detection of genes that increase susceptibility to major psychiatric disorders.

A latent variable model of developmental instability in relation to men's sexual behaviour

A single trait's fluctuating asymmetry (FA) is expected to be a poor measure of developmental instability. Hence, studies that examine associations between FA and outcomes expected to covary with developmental instability often have little power in detecting meaningful relationships. One way of increasing the power of detecting relationships between developmental instability and outcomes is through the use of multiple traits' FA. The way multiple traits have typically been used is in trait aggregates. Here, we illustrate another way of examining relationships with developmental instability using multiple traits' FA: through structural equation modelling. Covariances between measures of FA and an outcome variable are interpreted within the context of an explicit model of associations between variables, which is tested for fit and the parameters specified within the model are estimated. We used nine traits' FA as markers of a latent variable of men's developmental instability, which was associated with the number of sexual partners. The results indicate a sizeable correlation between developmental instability and men's sexual history, despite small correlations between individual traits' FA and sexual history.

Facial attractiveness signals different aspects of "quality" in women and men

We explored the relationships between facial attractiveness and several variables thought to be related to genotypic and phenotypic quality in humans (namely fluctuating asymmetry (FA), body mass index (BMI), health, age). To help resolve some controversy around previous studies, we used consistent measurement and statistical methods and relatively large samples of both female (n=94) and male (n=95) subjects (to be evaluated and measured), and female (n=226) and male (n=153) viewers (to rate attractiveness). We measured the asymmetry of 22 traits from three trait families (eight facial, nine body and five fingerprint traits) and constructed composite asymmetry indices of traits showing significant repeatability. Facial attractiveness was negatively related to an overall asymmetry index in both females and males, with almost identical slopes. Female facial attractiveness was best predicted by BMI and past health problems, whereas male facial attractiveness was best predicted by the socioeconomic status (SES) of their rearing environment. Composite FA indices accounted for a small (<4%) but usually significant percentage of the variation in facial attractiveness in both sexes, when factors related to asymmetry were controlled statistically. We conclude that, although facial attractiveness is negatively related to developmental instability (as measured by asymmetry), attractiveness also signals different aspects of "quality" in the two sexes, independent of FA.

Psychopathy and developmental instability

Psychopaths are manipulative, impulsive, and callous individuals with long histories of antisocial behavior. Two models have guided the study of psychopathy. One suggests that psychopathy is a psychopathology, i.e., the outcome of defective or perturbed development. A second suggests that psychopathy is a life-history strategy of social defection and aggression that was reproductively viable in the environment of evolutionary adaptedness (EEA). These two models make different predictions with regard to the presence of signs of perturbations or instability in the development of psychopaths. In Study 1, we obtained data on prenatal, perinatal, and neonatal signs of developmental perturbations from the clinical files of 643 nonpsychopathic and 157 psychopathic male offenders. In Study 2, we measured fluctuating asymmetry (FA, a concurrent sign of past developmental perturbations) in 15 psychopathic male offenders, 25 nonpsychopathic male offenders, and 31 male nonoffenders. Psychopathic offenders scored lower than nonpsychopathic offenders on obstetrical problems and FA; both psychopathic and nonpsychopathic offenders scored higher than nonoffenders on FA. The five offenders from Study 2 meeting the most stringent criteria for psychopathy were similar to nonoffenders with regard to FA and had the lowest asymmetry scores among offenders. These results provide no support for psychopathological models of psychopathy and partial support for life-history strategy models.

Developmental instability and working memory ability in children: a magnetic resonance spectroscopy investigation

This study of children (ages 7 through 12) wishes to determine (a) whether variation in frontal lobe brain chemistry, determined from proton magnetic resonance spectroscopy (1H-MRS), is related to performance on a working memory task in children, and (b) whether developmental instability (DI; the imprecise expression of the genetic plan for development due to several known genetic and environmental effects) underlies phenotypic variation in brain chemistry. 1H-MRS assessed neurometabolites in a right frontal white matter voxel. The Visual Two-Back test assessed working memory. A composite measure of DI was created from measures of minor physical anomalies, fluctuating asymmetry of body characteristics, and fluctuating asymmetry of dermatoglyphic features. Greater DI strongly predicted lower concentrations of creatine-phosphocreatine (Cre) and choline-containing compounds, whereas Cre and N-acetyl-aspartate positively correlated with working memory skills. Working memory skills thus seem related to frontal lobe energy metabolism, which in turn is related to DI.

Fingerprint ridge-count difference between adjacent fingertips (dR45) predicts upper-body tissue distribution: evidence for early gestational programming

Fingerprint ridge counts, which remain constant from the 19th week of pregnancy, are related to fingertip growth during early gestation. Each finger corresponds neurologically to a spinal-cord segment ranging from C6 (thumb, relatively cephalad) to C8 (fifth finger, relatively caudad). The authors hypothesized that large ridge-count differences between fingertips (cephalad > caudad) might reflect fetal inhibition of caudal growth. Among 69 male Atlanta, Georgia, military recruits (1994-1997; aged 17-22 years), they tested associations of the anthropometric waist-to-thigh ratio with 20 ridge-count differences. Waist-to-thigh ratio was associated with the ridge-count difference between the right fourth and fifth fingertips only (dR45; r = 0.36, p = 0.003). The race-adjusted standardized regression coefficient was 0.22 (95% confidence interval: 0.03, 0.41). Since upper-body tissue distribution indicates disease risk, the authors then tested the association of age (an indicator of survivorship) with dR45 in a sample of 135 male patients from Bangalore, India (1989-1990; aged 38-82 years). Age was inversely associated with dR45 (r = -0.17, p = 0.04), notably among the 75 men with diabetes (r = -0.22, p = 0.06). An increased dR45 predicts an upper-body tissue distribution originating before the midpoint of pregnancy. The cause of this developmental pattern is unknown, but it may lead to reduced survivorship.

A new symmetry-based scoring method for posture assessment: evaluation of the effect of insoles with mineral derivatives

BACKGROUND

There is a need for a validated rapid procedure for the evaluation of posture, defined as lateral balance/imbalance at the pelvic, shoulder, and neck levels. This would enable clinicians to determine the importance of symmetry in the pathophysiology of musculoskeletal disorders and to assess the efficacy of devices and treatments claiming to normalize or improve posture. In this investigation, the efficacy of such a device, a set of insoles with a hypothesized proprioceptive-like action, was evaluated through use of the described procedure.

OBJECTIVES

To develop a new scoring system to evaluate body posture on the basis of symmetry and to use this scoring system to investigate the efficacy of insoles containing a combination of mineral derivatives designed to balance posture through a neurophysiological effect.

METHODS

The posture score was based on the evaluation of 4 postural parameters: pelvic and shoulder lateral balance/imbalance, static shoulder rotation, and amplitude of head rotation. In the placebo-controlled study, 32 patients were tested in a double-blind fashion, either with placebo insoles or with insoles containing mineral derivatives. The same study was repeated in unblind conditions in 137 patients selected from 2 chiropractic clinics in an open-label protocol.

STUDY DESIGNS

A crossover placebo-controlled, double-blind study and a multicenter, large-scale, open-label study in patients selected from chiropractic clinics.

RESULTS

A basal postural evaluation in 137 patients revealed that no patient had a perfect symmetry-ie, a perfectly or nearly perfectly balanced posture. The insoles with mineral derivatives induced a highly significant and similar improvement in the postural score in both the crossover double-blind study (32 patients; 56.7% improvement) and the open-label study (137 patients; 60.7% improvement, P < 0.001).

CONCLUSIONS

All patients tested and selected in chiropractic clinics exhibited asymmetries and postural imbalances according to the newly developed scoring method, and this method was successful in assessing the efficacy of insoles exerting a profound and immediate postural effect through a hypothesized neurophysiological mode of action.

Developmental instability and schizotypy

INTRODUCTION

It has been suggested that evidence of developmental disturbance of cognition and lateralisation in schizophrenia can be best understood from the perspective of developmental stability (DS), an indicator of the extent to which an individual develops according to a specified ontogenic programme in the presence of environmental noise. Higher levels of fluctuating asymmetry (FA; the difference between right and left side of a quantitative morphological trait such as dermatoglyphics) are thought to reflect less DS. We examined this issue for dimensions of schizotypy.

METHODS

Associations between FA, measures of laterality and cognitive function on the one hand, and negative and positive dimensions of schizotypy on the other, were examined in a sample of 260 healthy adolescents aged 11.9-15.6years. FA was measured as a-b ridge count right-left differences. Neuropsychological measures yielded a general cognitive ability score and a frontal function score. Laterality was assessed with the Annett scale.

RESULTS

Measures of psychosis proneness were normally distributed. Negative schizotypy was associated with more FA and lower general cognitive ability in a dose-response fashion. The association with FA was more apparent in boys. No associations existed with laterality or frontal function.

CONCLUSION

The negative dimension of schizotypy may be associated with early developmental instability, resembling the pattern seen in the negative symptom dimension of schizophrenia. Measures of fluctuating asymmetry may be more sensitive with regard to the schizotypy phenotype than measures of laterality.

Phenotypic heterogeneity of growth and psychometric intelligence in Prader-Willi syndrome: variable expression of a contiguous gene syndrome or parent-child resemblance?

Phenotypic variability in children with Prader-Willi syndrome (PWS) was investigated with respect to variable expression of the contiguous gene syndrome and trait variance. In a prospective study, parent/child resemblance of anthropometric and psychometric measures was analyzed in 22 children with PWS (11 females and 11 males; 18 deletions, 4 uniparental disomy (UPD)) and in a control group (88 females and 88 males). The average child-midparent Z-score difference for height in females was -1.9 and in males -0.9, head circumference -1.7 and -1.0, and body mass index (BMI) 2.3 and 2.7, respectively. Intellectual performance of females and males was, on average, -2.7 and -2.6 below maternal performance. Range and standard deviation were moderately increased for height and head circumference, doubled for BMI, and unchanged for IQ. Parent/child correlations for anthropometric and psychometric measurements in the study group did not significantly differ from those of the control group. Exceptions were higher correlations between mothers and daughters for height (P < 0.05) and BMI (P < 0.01), and lower correlations for head circumference between midparent values and daughters (P < 0.05) than in the control group. In conclusion, parent-child resemblance in growth and intellectual development among children with PWS was found to be comparable to that noted in the normal population, indicating a strong determination by trait variance. Children with PWS differed significantly with respect to a lower trait level and-with the exception of IQ-a larger variability. The latter may indicate a variable expression of the contiguous gene syndrome.

Head trauma and intellectual status: relation to quantitative magnetic resonance imaging findings

This article contrasts 2 groups that sustained somewhat similar moderate to severe closed-head traumatic brain injury (TBI), but were deliberately selected to be different with regard to postinjury intellectual status--one group average or above, the other below. The purpose of this comparison was to describe any morphological characteristics of the 2 groups ascertained from quantitative magnetic resonance (QMR) imaging. Thirty-five TBI participants with Full Scale IQ (FSIQ) less than or equal to 90 were compared to 33 TBI participants whose FSIQ was above 90. A group of normal volunteer participants, age and gender matched, constituted a third magnetic resonance comparison group. All participants received uniform MRI from which QMR analysis was performed, including total cranial volume, subarachnoid cerebral spinal fluid ventricular volume, and hippocampal volume. Both TBI groups received neuropsychological testing in the course of clinical follow-up. Morphological comparisons between groups were made using multivariate analysis of variance. The TBI group with an IQ less than or equal to 90 had significantly enlarged third and temporal horn compartments. Total intracranial volume was smaller in this group as well. Lower psychometric intelligence postinjury may be associated with more temporal lobe atrophy and subcortical pathology. Smaller premorbid brain size may be another risk factor.

Birth order and fluctuating asymmetry: a first look

We investigated the hypothesis that maternal immunoreactivity to male-specific features of the foetus can increase developmental instability. We predicted that the participants' number of older brothers would be positively related to the fluctuating asymmetry of ten bilateral morphological traits. The participants were 40 adult male psychiatric patients and 31 adult male hospital employees. Consistent with the hypothesis, the participants' number of older brothers--but not number of older sisters, younger brothers or younger sisters--was positively associated with fluctuating asymmetry. The patients had significantly larger fluctuating asymmetry scores and tended to have more older brothers than the employees, but the positive relationship between the number of older brothers and fluctuating asymmetry was observed in both groups.

The evolutionary genetic underpinnings of schizophrenia: the developmental instability model

The importance of genes in the etiology of schizophrenia is well known, but the manner in which the relevant genomic factors influence neural development and the nature of selection forces operating on these factors are poorly understood. In several prominent papers, Crow has provided a unique and comprehensive theory that attempts to deal with these issues. A central aspect of his theory is that a single gene leads to reduced cerebral lateralization, increased ventricular size, and risk for developing schizophrenia. He relies greatly on Annett's right shift theory of individual variation in handedness. An alternative approach, based on the construct of developmental instability, provides a different way to conceptualize genetic influences, selection forces, and atypical lateralization in schizophrenia. We suggest that the developmental instability model has stronger empirical support and is better grounded in contemporary evolutionary genetics.

Human body odour, symmetry and attractiveness

Several studies have found body and facial symmetry as well as attractiveness to be human mate choice criteria. These characteristics are presumed to signal developmental stability. Human body odour has been shown to influence female mate choice depending on the immune system, but the question of whether smell could signal general mate quality, as do other cues, was not addressed in previous studies. We compared ratings of body odour, attractiveness, and measurements of facial and body asymmetry of 16 male and 19 female subjects. Subjects wore a T-shirt for three consecutive nights under controlled conditions. Opposite-sex raters judged the odour of the T-shirts and another group evaluated portraits of the subjects for attractiveness. We measured seven bilateral traits of the subject's body to assess body asymmetry. Facial asymmetry was examined by distance measurements of portrait photographs. The results showed a significant positive correlation between facial attractiveness and sexiness of body odour for female subjects. We found positive relationships between body odour and attractiveness and negative ones between smell and body asymmetry for males only if female odour raters were in the most fertile phase of their menstrual cycle. The outcomes are discussed in the light of different male and female reproductive strategies.