Influence of the initial projection of the centre of gravity on posturo-kinetic coordination in humans. Application from a horizontal quadrupedal stance during voluntary limb raising

The purpose of the study is to investigate the influence of initial projection of the centre of gravity (CG) on the spatial and temporal organization of the dynamic phenomena accompanying a voluntary movement in humans. From a horizontal quadrupedal stance, ten normal subjects were instructed to raise the right forelimb towards a support target in self paced velocity conditions. Three experimental conditions were tested for which the initial CG projection was either within (C1), at the limits of (C2) or outside the supporting triangle (C3). The results showed that vertical force variations on the four supports always preceded the first vertical displacement of the right wrist (onset of the movement). From C1 to C3, the duration of these anticipatory dynamic phenomena increased enabling an adjustment of the CG position such that equilibrium constraints were fulfilled. For all conditions, the acceleration peak of the CG occurred prior to the onset of movement and from C1 to C3, its magnitude increased in a single direction of the horizontal plane. For each condition, the load transfer was directed to the left forelimb and the right hindlimb (diagonal strategy) and reached a maximal value at the time of lift-off. With respect to this moment, the onset of the movement occurred increasingly early from C1 to C3. These results suggest that contribution of peripheral cues to postural control is more important, when the requirements of horizontal CG displacement increase.     

Is fluency free-operant response-response chaining?

This article briefly reviews behavioral fluency and its 10 products. Fluency development requires three of the four free-operant freedoms: the freedom to present stimuli at the learner's rhythm, the freedom to form the response, and the freedom to speed at the learner's maximum frequency. The article closes with several suggestions that fluent performing is really operant response-response (R-R) chaining, and recommends further controlled laboratory research on free-operant R-R chaining.     

Psychopathic personality traits and temporal perspective: A test of the short time horizon hypothesis

A number of authors have proposed that psychopathic individuals possess an abnormally constricted time horizon (i.e., foreshortened sense of the future). This hypothesis was tested among 101 undergraduates, who were administered a battery of (1) self-report indices of psychopathic personality traits, antisocial behavior, and normal-range personality traits; (2) self-report indices of time perspective; (3) projective tests of time perspective; and (4) laboratory tasks assessing time estimation and capacity for foresight and impulse control. Measures of psychopathy/antisocial behavior tended to be negatively correlated with several self-report indices assessing preoccupation with the future and with a projective task assessing the frequency of thoughts concerning future events, although only one of the correlations with this latter task was significant. In most cases these correlations were not attributable to the variance shared by measures of psychopathy/antisocial behavior and measures of (low) anxiety-proneness, although several correlations decreased substantially after levels of harmavoidance were controlled. In contrast, measures of psychopathy/antisocial behavior were negligibly correlated with laboratory tasks. These results provide mixed support for the short time horizon hypothesis and suggest that further attention to the role of method factors in investigations of future time perspective is warranted.     

Why a feminist approach to bioethics?

Many have asked how and why feminist theory makes a distinctive contribution to bioethics. In this essay, I outline two ways in which feminist reflection can enrich bioethical studies. First, feminist theory may expose certain themes of androcentric reasoning that can affect, in sometimes crude but often subtle ways, the substantive analysis of topics in bioethics; second, it can unearth the gendered nature of certain basic philosohical concepts that form the working tools of ethical theory.     

Reduction of the elevator illusion from continued hypergravity exposure and visual error-corrective feedback

Ten subjects served as their own controls in two conditions of continuous, centrifugally produced hypergravity (+2 Gz) and a 1-G control condition. Before and after exposure, open-loop measures were obtained of (1) motor control, (2) visual localization, and (3) hand-eye coordination. During exposure in the visual feedback/hypergravity condition, subjects received terminal visual error-corrective feedback from their target pointing, and in the no-visual feedback/hypergravity condition they pointed open loop. As expected, the motor control measures for both experimental conditions revealed very short lived underreaching (the muscle-loading effect) at the outset of hypergravity and an equally transient negative aftereffect on returning to 1 G. The substantial (approximately 17°) initial elevator illusion experienced in both hypergravity conditions declined over the course of the exposure period, whether or not visual feedback was provided. This effect was tentatively attributed to habituation of the otoliths. Visual feedback produced a smaller additional decrement and a postexposure negative aftereffect, possible evidence for visual recalibration. Surprisingly, the target-pointing error made during hypergravity in the no-visual-feedback condition was substantially less than that predicted by subjects’ elevator illusion. This finding calls into question the neural outflow model as a complete explanation of this illusion.     

Folic acid and the prevention of neural tube defects: A position paper of the national society of genetic counselors

Considerable scientific evidence demonstrates the reduction in risk for neural tube defects (NTDs) associated with maternal preconceptional folic acid supplementation. The National Society of Genetic Counselors (NSGC) endorses the U.S. Public Health Service recommendations for folic acid supplementation at the 0.4 mg level for women in the general population and at the 4.0 mg level for women at high or increased risk for NTD pregnancies for at least 4 weeks prior to active pursuit of conception. We encourage targeted educational efforts and surveillance to assess results of this dietary supplementation. The NSGC further urges the Food and Drug Administration to fortify staple foodstuffs with folic acid for a population-based approach to minimize the number of NTD births.     

The impact of confederate responsivity on social skills assessment

The current investigation examined the degree to which judges' ratings of skill, anxiety, and attractiveness are influenced by the responsivity of the confederate. High-, medium-, and low-skilled subject-pool groupings, as well as self-referred clinical groups, were exposed to either a moderately or a minimally responsive confederate. Results indicated that subjects were rated as more skillful when interacting with a moderately responsive confederate than when interacting with a minimally responsive confederate. Further, there was a groups × condition interaction for anxiety ratings such that both the high- and the medium-skilled groups appeared more anxious under the minimal condition, whereas the low-skilled and self-referred groups did not. Self-referred subjects received significantly lower attractiveness ratings than did the high- or medium-skilled groups. Implications of these results and future directions for research are discussed.This research is based on a M.S. thesis carried out by the first author under direction of the second author.