Genetic and environmental structure of Cloninger's temperament and character dimensions

The multivariate genetic and environmental structure of Cloninger's Temperament and Character Inventory (TCI) was investigated in a sample of 617 pairs of adolescent and young adult twins from Japan. Additive genetic factors accounted for 22% to 49% of the variability on all TCI temperament scales. Although the theory predicts lower heritability for the character scales, all character subscales had a substantial genetic contribution, and nonshared environmental influences accounted for the remainder. Multivariate genetic analyses showed that several subscales used to define one dimension shared a common genetic basis with subscales defining others. Using the degree of shared genetic influence as the basis to rearrange the TCI subscales into new dimensions, it was possible to create genetically independent scales. The implications for personality measurement, theory, and molecular genetic research are discussed.     

Development of carefulness and quickness observed for a tray-carrying task

The purpose of this study was to investigate the developmental change in performance of groups of children instructed to behave carefully and quickly in a tray-carrying task. The subjects were 69 nonhandicapped children from a kindergarten, ages 3-4 to 6 years, and 20 adult students who volunteered. Subjects were instructed to carry as fast as they could a tray with a glass of water for 3 m without a spill. The amounts of water spilled and the times taken were measured. The amounts of water spilled were hardly different within groups of children of the same ages or between age groups. But the times were different among groups: the younger ones took longer, and the difference in time between tray-carrying and normal walking was greatest for the youngest group. Children could carry the tray as carefully as adults but could not do so quickly. The nature of the representation of the instruction in relation to the behavior of children and the difference in strategy to guarantee carefulness between children and the adults are discussed.     

Substance and artifact in the higher-order factors of the Big Five

J. M. Digman (1997) proposed that the Big Five personality traits showed a higher-order structure with 2 factors he labeled alpha and beta. These factors have been alternatively interpreted as heritable components of personality or as artifacts of evaluative bias. Using structural equation modeling, the authors reanalyzed data from a cross-national twin study and from American cross-observer studies and analyzed new multimethod data from a German twin study. In all analyses, artifact models outperformed substance models by root-mean-square error of approximation criteria, but models combining both artifact and substance were slightly better. These findings suggest that the search for the biological basis of personality traits may be more profitably focused on the 5 factors themselves and their specific facets, especially in monomethod studies.     

Temporal and spatial parameters of stepping in place in children and adults

Characteristics of synchronized and self-paced stepping in place were examined by analyzing a temporal parameter (step frequency) and a spatial parameter (step height). Participants were 20 adults (10 women, 10 men; M age = 22.5 yr., range = 21-23) and 10 children (5 girls, 5 boys; M age=6.1 yr., range = 5-6). Results indicated that: (1) the step frequencies, which were equivalent for both groups, were well coincident with stimulus frequencies; (2) when step frequencies were imposed, the step height decreased with increasing step frequency, except for the lowest frequency condition in children; (3) movement consistency was the highest at 2 Hz and deteriorated if the step frequency was higher or lower; and (4) the self-paced stepping in place was optimal in terms of movement consistency. These results showed that stepping in place is a rhythmic movement at a given range of frequency which is coordinated so as to keep the product of step frequency and step height constant.     

Measuring Socio-economic Factors and Sensitivity of Happiness

There is significant variation in average subjective well-being across countries. What makes people in some countries happier or more miserable than others? In this study, we decompose the difference in average subjective well-being across countries into a comprehensive set of socio-economic factors along with cross-country difference in sensitivity of happiness in order to answer the question. While an individual’s subjective well-being is affected by socio-economic status, every individual does not necessarily draw the same level of subjective well-being from a given condition of life because of different personal characteristics. Sensitivity of happiness is an umbrella term capturing such factors that are not reflected by socio-economic conditions. We introduce Data Envelopment Analysis (DEA) approach to estimate a happiness function and specify the sensitivity score for each country in a sample. We draw on a comprehensive set of well-being indicators released by the Better Life Initiative of the OECD, along with measures of income inequality. We find that the health factor and sensitivity term play the largest role in generating variation in subjective well-being. Even within countries, the average level of subjective well-being varies between different population groups. Drawing on a set of indicators that assess the life circumstances of different groups within each country, our decomposition formulation allows for a full explanation of the differences in average life satisfaction between the groups. We investigate the differences between men and women, and high income earners and low income earners.     

Binocular rivalry alternation rate declines with age

The effect of aging on the time of spontaneous perceptual alternation in binocular rivalry was examined in 59 subjects. An earlier study reported the change of alternation time by comparing middle-age and elderly subjects. We also observed age-related prolongation in alternation time by comparing subjects in a lower age group (20-34 years) with those in both a middle-age group (35-49 years) and a higher age group (50-64 years). Aging of visual optical functions such as presbyopia or the reduction of contrast sensitivity has an accelerating effect over age and may not be related to the age-associated monotonic prolongation of alternation time in binocular rivalry. The origin of aging in binocular rivalry is still unclear but a neural interval generator for perceptual switching is suggested.     

Perception of gaze direction based on luminance ratio

Changing the luminance of one side of the sclera induces an apparent shift of the perceived direction of gaze toward the darker side of the sclera (Ando, 2002 Perception 31 657-674). However, when both the sclera and the skin surrounding it were darkened simultaneously as if by a cast shadow, the apparent direction of gaze shifted less than when only the sclera was darkened. The results suggest that one mechanism for gaze judgment is based on a simple analysis of the local luminance ratio between the eye and the surrounding region.