Heritability of item responses on the Eysenck personality questionnaire

We report estimates of the heritabilities and common environment variances for the 90 items of the Eysenck Personality Questionnaire. Responses from 627 pairs of twins were analysed using the biometrical genetic analysis based on the threshold model described by Falconer. Many of the items revealed very substantial heritabilities. No less than 67/90 had heritabilities > 33%, 19 had > 50% and a few were even > 65%. Some of the useful implications of item heritabilities are discussed.     

Principal components analysis of sampled functions

This paper describes a technique for principal components analysis of data consisting ofn functions each observed atp argument values. This problem arises particularly in the analysis of longitudinal data in which some behavior of a number of subjects is measured at a number of points in time. In such cases information about the behavior of one or more derivatives of the function being sampled can often be very useful, as for example in the analysis of growth or learning curves. It is shown that the use of derivative information is equivalent to a change of metric for the row space in classical principal components analysis. The reproducing kernel for the Hilbert space of functions plays a central role, and defines the best interpolating functions, which are generalized spline functions. An example is offered of how sensitivity to derivative information can reveal interesting aspects of the data.This research was supported by Grant PA 0320 to the second author by the Natural Sciences and Research Council of Canada. We are grateful to the reviewers of an earlier version and to J. B. Kruskal and S. Winsberg for many helpful comments concerning exposition.     

Channel surfing in the visual brain

Vision provides us with an ever-changing neural representation of the world from which we must extract stable object categorizations. We argue that visual analysis involves a fundamental interaction between the observer's top-down categorization goals and the incoming stimulation. Specifically, we discuss the information available for categorization from an analysis of different spatial scales by a bank of flexible, interacting spatial-frequency (SF) channels. We contend that the activity of these channels is not determined simply bottom-up by the stimulus. Instead, we argue that, following perceptual learning a specification of the diagnostic, object-based, SF information dynamically influences the top-down processing of retina-based SF information by these channels. Our analysis of SF processing provides a case study that emphasizes the continuity between higher-level cognition and lower-level perception.     

Influence of postural regulation in male judokas' direction of falls

In competitions, judokas tend to have a predominant direction of fall: forwards or backwards. A relationship was hypothesized between the direction of fall and certain parameters of the judokas' postural activities. 20 judokas, 16 to 19 yr. old (17.7 +/- 0.4 yr.), had practised judo for at least seven years. They were separated into two groups. The group of forward fallers (n = 9) and the group of backward fallers (n = 11) performed posturokinetic tests to assess their static and dynamic balance. One parameter assessed through the analysis of postural activities, the average position of anteroposterior dynamic oscillations, was inversely related to the judokas' direction of fall. Postural activities might not play a direct role but perhaps an indirect one in the direction of falls by expert judokas.     

The impact of parental borderline personality disorder on vulnerability to depression in children of affectively ill parents

Children of parents with major depressive disorder (MDD) are four to six times more likely than other children to develop MDD. Little research has examined whether comorbid parental diagnoses further increase children's risk. This study examines whether children of parents with comorbid MDD and Borderline Personality Disorder (BPD) (1) are at greater risk for experiencing depressive symptoms and/or episodes and (2) whether such increased risk may be due, in part, to their exhibiting higher levels of cognitive/interpersonal vulnerability factors. Children (n = 140; ages 6-14) of parents with MDD completed measures assessing cognitive/interpersonal vulnerability factors. Parents completed semi-structured clinical interviews assessing severity of current depressive symptoms and BPD. Both children and parents completed a semi-structured clinical interview assessing the child's current and past history of MDD. Children of parents with comorbid MDD and BPD exhibited higher levels of current depressive symptoms and higher levels of cognitive/interpersonal vulnerability factors than children of parents with MDD but no BPD, even after controlling for parents' current levels of depressive symptoms. The relationship between parental BPD and chil-dren's current levels of depressive symptoms was partially mediated by children's cognitive/interpersonal vulnerability factors. Last, children of parents with comorbid BPD and MDD were 6.84 times more likely to exhibit a current or past diagnosis of MDD.     

GPS analysis of human locomotion: further evidence for long-range correlations in stride-to-stride fluctuations of gait parameters

During free walking, gait is automatically adjusted to provide optimal mechanical output and minimal energy expenditure; gait parameters, such as cadence, fluctuate from one stride to the next around average values. It was described that this fluctuation exhibited long-range correlations and fractal-like patterns. In addition, it was suggested that these long-range correlations disappeared if the participant followed the beep of metronome to regulate his or her pace. Until now, these fractal fluctuations were only observed for stride interval, because no technique existed to adequately analyze an extended time of free walking. The aim of the present study was to measure walking speed (WS), step frequency (SF) and step length (SL) with high accuracy (<1 cm) satellite positioning method (global positioning system or GPS) in order to detect long-range correlations in the stride-to-stride fluctuations. Eight participants walked 30 min under free and constrained (metronome) conditions. Under free walking conditions, DFA (detrended fluctuation analysis) and surrogate data tests showed that the fluctuation of WS, SL and SF exhibited a fractal pattern (i.e., scaling exponent alpha: 0.5 < alpha < 1) in a large majority of participants (7/8). Under constrained conditions (metronome), SF fluctuations became significantly anti-correlated (alpha < 0.5) in all participants. However, the scaling exponent of SL and WS was not modified. We conclude that, when the walking pace is controlled by an auditory signal, the feedback loop between the planned movement (at supraspinal level) and the sensory inputs induces a continual shifting of SF around the mean (persistent anti-correlation), but with no effect on the fluctuation dynamics of the other parameters (SL, WS).     

Synchrony in the onset of mental-state reasoning: evidence from five cultures

Over the past 20 years, developmental psychologists have shown considerable interest in the onset of a theory of mind, typically marked by children's ability to pass false-belief tasks. In Western cultures, children pass such tasks around the age of 5 years, with variations of the tasks producing small changes in the age at which they are passed. Knowing whether this age of transition is common across diverse cultures is important to understanding what causes this development. Cross-cultural studies have produced mixed findings, possibly because of varying methods used in different cultures. The present study used a single procedure to measure false-belief understanding in five cultures: Canada, India, Peru, Samoa, and Thailand. With a standardized procedure, we found synchrony in the onset of mentalistic reasoning, with children crossing the false-belief milestone at approximately 5 years of age in every culture studied. The meaning of this synchrony for the origins of mental-state understanding is discussed.