Genetic and Environmental Sex Differences in Mental Rotation Ability: A Japanese Twin Study

Mental rotation and schizotypal personality traits: A Bayesian approach

People diagnosed with schizophrenia exhibit mental rotation differences, suggesting that clinical levels of positive symptoms, such as psychotic hallucinations, are related to disruptions in their monitoring and manipulation of mental representations. According to the psychosis continuum, findings in people with a high level of schizotypal personality traits are expected to be qualitatively similar, but research concerning this topic is scarce. A spared mental imagery manipulation in this population only could suggest that this ability might be a possible protective factor, or that the emergence of clinical-level positive symptoms could be paired with disruptions in this capacity. To explore this issue, 205 undergraduate students (122 women) completed a novel mental rotation task identifying the stimulus that was a 90, 180, or 270° rotation of a black circle with colored portions and were assessed with the Schizotypal Personality Questionnaire. Men performed better in most conditions. No relationship was detected between schizotypal personality traits and accuracy in the task. These results do not support that mental imagery manipulation disruptions may be related to schizotypal personality traits in non-clinical populations. Thus, they might instead be associated with the onset of psychosis disorders as mental representation handling is hindered. However, additional research is required including the general population, as well as those with higher levels of psychotic symptoms and psychosis disorders. Future research could also focus on working memory processes related to mental representation manipulations of different sensory modalities such as auditory mental representations and their relationship with schizotypal personality traits and clinical populations.

Item type, occlusion, and gender differences in mental rotation

Two experiments were conducted to examine the role of item type in mental rotation. In each experiment, participants completed two computerized mental rotation tasks, one with blocks as stimuli and one with human figures as stimuli. The tasks were formatted either as a multiple-choice psychometric test (Experiment 1) or as a same–different type task (Experiment 2). Aside from the expected replication of a decreased effect of occlusion on women's accuracy when processing human figures compared to block figures, it was hypothesized that response times would increase when processing the complex but familiar human figures, compared to the simple but unfamiliar block figures. In Experiment 1, the results relevant to occlusion were replicated. However, the presence of a speed–accuracy trade-off suggested that participants processed human figures faster but less accurately than block figures. In Experiment 2, both men and women performed faster and more accurately when processing occluded human figures than when processing nonoccluded human figures. The effect of item type, its potential link to embodied cognition, and the role of strategy selection on gender differences in mental rotation are discussed.

Relation of intelligence quotient and body mass index in preschool children: a community-based cross-sectional study

OBJECTIVE

Overweight and obesity in children is a global problem. Besides physical effects, obesity has harmful psychological effects on children.

METHODS

We carried out cross-sectional community-based study to investigate the relation between body mass index (BMI) and cognitive functioning in preschool children. Thirteen socioeconomical elements of 1151 children were measured and analyzed based on their intelligence quotient (IQ) test results. Thirteen out of 33 provinces were selected randomly, and schools were selected as clusters in rural and urban areas. Descriptive statistics, t-test, analysis of variance and regression were used when appropriate.

RESULTS

Our analysis showed that IQ was associated with household income, place of residence, delivery type, type of infant feeding and father's and mother's education level (P<0.001 for all). Using penalized linear regression for eliminating the impact of confounding factor, our study shows that, living in metropolitan (β=2.411) and urban areas (β=2.761), the level of participants' father's education (β=5.251) was positively and BMI (β=-0.594) was negatively related with IQ test results.ConclusionsThe findings of the present study showed that a lower IQ score is associated with higher BMI. However, this relation appears to be largely mediated when the socioeconomic status was considered.

Two Cohort and Three Independent Anonymous Twin Projects at the Keio Twin Research Center (KoTReC)

The Keio Twin Research Center has conducted two longitudinal twin cohort projects and has collected three independent and anonymous twin data sets for studies of phenotypes related to psychological, socio-economic, and mental health factors. The Keio Twin Study has examined adolescent and adult cohorts, with a total of over 2,400 pairs of twins and their parents. DNA samples are available for approximately 600 of these twin pairs. The Tokyo Twin Cohort Project has followed a total of 1,600 twin pairs from infancy to early childhood. The large-scale cross-sectional twin study (CROSS) has collected data from over 4,000 twin pairs, from 3 to 26 years of age, and from two high school twin cohorts containing a total of 1,000 pairs of twins. These data sets of anonymous twin studies have mainly targeted academic performance, attitude, and social environment. The present article introduces the research designs and major findings of our center, such as genetic structures of cognitive abilities, personality traits, and academic performances, developmental effects of genes and environment on attitude, socio-cognitive ability and parenting, genes x environment interaction on attitude and conduct problem, and statistical methodological challenges and so on. We discuss the challenges in conducting twin research in Japan.