Specifying importance weights consistent with a covariance structure

Many situations exist in which multiple dimensions must be combined to create a composite which reflects overall utility or value to a decision maker. A linear combination is often used in which the decision maker's importance weights are multiplied by values of each dimension and then added. When the decision maker's weights are applied, however, the dimension values must have equal variance and essentially zero correlations, or else the ordering on the composite will be incorrect. In this paper, we provide a method which compensates for dimension correlation and inequality of dimension variance. The method is illustrated with ratings of modifications proposed for nuclear power plants.     

Adaptive memory: fitness relevant stimuli show a memory advantage in a game of pelmanism

A pelmanism (matched-pairs) game was used in order to test the hypothesis that survival-relevant stimuli that are likely to have been present during human evolution (e.g., a snake in attack position) enjoy a memory advantage over other survival-relevant (but “modern”) stimuli (e.g., a threatening image of a gunman). Survival-relevant stimuli were matched for arousal and presented in one of two 5 x 4 grids, along with filler items. Participants were asked to match the pairs in the grids by clicking on successive squares to reveal stimuli. Participants made significantly fewer errors when matching evolutionarily relevant survival stimuli than when matching the other stimuli. Additionally, on incorrect trials, the attempted matches were significantly closer to the actual locations of evolutionarily relevant targets than to those of other stimuli. The results suggest that objects that likely posed a consistent threat throughout human evolutionary history are better remembered than other, equally arousing and survival-relevant, stimuli. [corrected]     

Visuospatial bootstrapping: Long-term memory representations are necessary for implicit binding of verbal and visuospatial working memory

It has recently been shown that presenting additional visuospatial information alongside to-be-remembered numbers in a digit span task enhances participants’ memory for those items. However, the mechanisms behind this visuospatial bootstrapping effect have remained unspecified. In this article, we report evidence that this effect involves an integration of information from verbal and visuospatial temporary memory with long-term-memory (LTM) representations and that the existence of a relevant LTM representation is necessary for bootstrapping to occur.     

Changes in the variability of movement trajectories with practice

We studied variability in movement phase plane trajectories (velocity-position relation) during movement. Human subjects performed 10 degrees and 30 degrees elbow flexion and extension movements in a visual step tracking paradigm. The area of ellipses with radii equal to one standard deviation in position and velocity was taken as a measure of trajectory variability. Trajectory variability was determined at 10-ms intervals throughout movements. Trajectory variability in both the acceleration and deceleration phases of movement decreased with practice. The average trajectory variability during deceleration was greater than that during acceleration even after extended practice (1000 trials). During practice, subjects usually increased movement speed while maintaining end-position accuracy. Trajectory variability was also related to movement speed when equal amounts of practice were given. Short duration (fast) movements had greater trajectory variability than long duration movements. Thus there is a tradeoff between movement speed and trajectory variability similar to the classical speed-accuracy tradeoff. Trajectory variability increased rapidly during the acceleratory phase of movement. The rate of increase was positively related to both movement amplitude and speed. Thus, the forces producing limb acceleration were variable and this variability was more marked in faster and larger movements. In contrast, trajectory variability increased more slowly or actually decreased during the deceleratory phase of movements. Forces involved in limb deceleration thus appeared to compensate to a greater or lesser degree for the variability in accelerative forces. The experiments indicate that the entire trajectory of simple limb movements is controlled by the central nervous system. Variations in accelerative forces may be compensated for by associated variations in decelerative forces. The linkage between accelerative and decelerative forces is progressively refined with practice resulting in decreased variability of the movement trajectory.     

A linked muscular activation model for movement generation and control

A new model for movement control is presented which incorporates characteristics of impulse-variability and mass-spring models. Movements in the model were controlled with phasic torque impulses in agonist and antagonist muscles and a tonic agonist torque. Characteristics of the phasic agonist and antagonist torque profiles were based on observed properties of movement-related EMGs and muscle isometric torques. Variability of the phasic impulses depended on impulse magnitude as in impulse-variability models. The model therefore predicted a speed-accuracy tradeoff for limb movement. The time of onset and magnitude of the antagonist torque depended on the magnitude of the preceding agonist torque as indicated in studies of movement-related EMGs. This led to the new concept of linkage between the agonist and antagonist muscle forces which was shown to be important for reducing variability of fast movements. Progressive development of linkage during practice could explain the previous findings of decreased movement variability with practice coupled with increased variability of movement-related EMGs. It was concluded that an inherently variable motor system deals with the variability associated with generation of large muscle forces by linking the forces produced by opposing muscles. In this way, variability in net joint torques and in movements can be decreased without the need for the nervous system to closely regulate the individual torques.     

A perinatal ethics committee on abortion: process and outcome in thirty-one cases.

The US Supreme Court's June 1992 decision to uphold most of Pennsylvania's law restricting access to abortion confirms that while abortion is still permitted in the US, it is being increasingly regulated. Individual institutions may, however, find ways to permit access to abortion. One hospital formed a mandatory, prospective perinatal ethics committee (PEC) in May 1987 to develop clinical guidelines with which to consider and decide requests by physicians for their patients seeking abortions. The authors obtained the consent of this PEC to study its membership, processes, case outcomes, and clinical decision making. Understanding PEC processes and outcomes may help other institutions to decide whether to institute similar mechanisms. Specifically, the investigators determined the backgrounds and abortion-related beliefs of PEC members and obstetric and gynecology department members, whether the PEC affects the number of abortions performed, how PEC members decide in individual cases, and whether requesting physicians find the PEC helpful. All eleven PEC members and 58 of the 65 medical staff ob/gyn physicians returned background surveys. Study results are presented. Overall, the PEC appeared to function as an affirming regulatory body for second-trimester, medically-indicated terminations and for certain personal choice terminations. Institutional interests were well-served by the PEC and with the assurance of informed consent, the interests of some patients were also well served.     

Representational Pseudoneglect: A Review

Pseudoneglect, the tendency to be biased towards the left-hand side of space, is a robust and consistent behavioural observation best demonstrated on the task of visuospatial line bisection, where participants are asked to centrally bisect visually presented horizontal lines at the perceived centre. A number of studies have revealed that a representational form of pseudoneglect exists, occurring when participants are asked to either mentally represent a stimulus or explore a stimulus using touch in the complete absence of direct visuospatial processing. Despite the growing number of studies that have demonstrated representational pseudoneglect there exists no current and comprehensive review of these findings and no discussion of a theoretical framework into which these findings may fall. An important gap in the current representational pseudoneglect literature is a discussion of the developmental trajectory of the bias. The focus of the current review is to outline studies that have observed representational pseudoneglect in healthy participants, consider a theoretical framework for these observations, and address the impact of lifespan factors such as cognitive ageing on the phenomenon.     

Parental Indulgence: Profiles and Relations to College Students’ Emotional and Behavioral Problems

Research on indulgent parenting and its relation to college students is both limited and inconsistent. Further, all the studies have used a variable-centered approach. To fill the gap in the current literature, the aims of this study were to explore profiles of parental indulgence and their associations with college students’ emotional and behavioral problems. The sample in this study consisted of college students from two universities. Participants were asked to take an online survey about their perceptions of their parents’ indulgent parenting practice and their own well-being. Results from latent profile analyses suggested distinct profiles of parental indulgence for mothers and fathers. Further, these profiles demonstrated differential associations with college students’ anxiety and depressive symptoms, emotional dysregulation, and alcohol use. Implications were also noted.     

Procrastination,Flow, and Academic Performance in Real Time Using the Experience Sampling Method

The authors' aim was to first provide an alternative methodology in the assessment of procrastination and flow that would not reply on retrospective or prospective self-reports. Using real-time assessment of both procrastination and flow, the authors investigated how these factors impact academic performance by using the Experience Sampling Method. They assessed flow by measuring student self-reported skill versus challenge, and procrastination by measuring the days to completion of an assignment. Procrastination and flow were measured for six days before a writing assignment due date while students (n = 14) were enrolled in a research methods course. Regardless of status of flow, both the nonflow and flow groups showed high levels of procrastination. Students who experienced flow as they worked on their paper, in real time, earned significantly higher grades (M = 3.05 ± 0.30: an average grade of B) as compared with the nonflow group (M = 1.16 ± 0.33: an average grade of D; p = .007). Additionally, students experiencing flow were more accurate in predicting their grade (difference scores, flow M = 0.12 ± 0.33 vs. nonflow M = 1.39 ± 0.29; p = .015). Students in the nonflow group were nearly a grade and a half off in their prediction of their grade on the paper. To the authors' knowledge, the study is the first to provide experimental evidence showing differences in academic performance between students experiencing flow and nonflow students.