Sex Differences in Variability in Vocational Interests: Evidence from Two Large Samples

Greater male variability has been established in cognitive abilities and physical attributes. This study investigated sex differences in variability in vocational interests with two large samples (N > 40 000 and N > 70 000). The results show that although men varied more in Realistic and Enterprising interests, women varied more in Artistic and Conventional interests. These differences in variability had considerable influence on the female–male tail ratios in vocational interests that have been found to contribute to reported gender disparities in certain fields of work and academic disciplines. Moreover, differences in means and variability interacted non‐linearly in shaping tail‐ratio imbalances. An age‐specific analysis additionally revealed that differences in variability diminished with age: Older samples showed smaller differences in variance in Realistic, Artistic, and Social interests than younger samples. Thus, I found no evidence that greater male variability applies for vocational interests in general. Copyright © 2015 European Association of Personality Psychology     

The role of preference in speed choice

Individual differences with regard to speed preference may be a source of speed heterogeneity and conflicts in traffic, such as tailgating and dangerous overtaking. The main aim of the current study was to explore drivers’ speed preferences when driving for different reasons (saving money on fuel, driving safely, driving for fun or driving as usual) and the relationship of these preferences to observed speeds and self-reported speed. 193 drivers were interviewed at five different locations, and were asked about their speeds on roads they had just travelled. Drivers’ speeds on these roads were also sampled with a speed gun. The results showed large differences between speeds chosen for different driving purposes; the lowest speeds were chosen when the goal was economy and the highest when driving for fun. In addition, there were individual differences in speed preferences such that some drivers indicated that their usual speed was above what they believed was a safe speed while others indicated that they usually drove even slower than what they thought was safe. These differences may account for much of the speed heterogeneity observed in on-road behaviour. The results also showed that drivers’ speed choices are highly influenced by their usual speeds, even more so than their beliefs regarding what constitutes a safe speed, which may help explain non-compliance with speed limits. No relationship was found between speed choice and risk perception.     

The central tendency of a social group can affect ratings of its intragroup variability in the absence of social identity concerns

People report less variability within in-groups than within out-groups when they make their ratings on traits on which the in-group has a higher central tendency than the out-group. [Simon, 1992a] and [Simon, 1992b] proposed that this effect is motivated by the need to protect a positive social identity. The present research tested the necessity of the social identity motive by using participants who were not members of any of the target groups that they judged. In Study 1 (N = 60), psychology undergraduate students reported significantly less intragroup variability on positive traits among a group of fashion designers that won a fashion competition than among a group that lost. Study 2 (N = 75) found a reverse effect on negative traits and confirmed the mediating role of perceived central tendency. These results demonstrate that the social identity motive is not necessary to explain the effect of central tendency on ratings of intragroup variability, and that the effect is more general than previously reported.     

Variability and Determinism in Motor Behavior

In investigations into perception-action systems, variability of observable behavior may be considered to (a) interfere with inquiry, (b) be neither detrimental nor particularly useful to inquiry, or (c) play a crucial role in inquiry. The authors underscore recent suggestions that alternative (c) is a preferred strategy for the study of many motor behaviors. In tutorial fashion, the authors review the concepts of variability and determinism with respect to postural and rhythmic movements. Study of the variability of those behaviors has revealed crucial features suggestive of underlying mechanisms and control, such as particular blends of noise and determinism (piecewise determinism). It has also revealed general lessons (for example, more variable does not mean more random and more controllable does not mean more deterministic) that may extend to other classes of perceptual-motor behavior.     

Force Control Is Greater in the Upper Compared With the Lower Extremity

The authors investigated whether force control is similar between the upper and lower limbs and between contractions that involve 1 or 2 joints. Six volunteers (27.5 ± 11.2 years of age) attempted to produce consistent discrete rapid force responses of 30, 60, and 90 N by using 6 different body postures, 3 with the upper and 3 with the lower limb. One of the postures for each limb involved 2 joints. The standard deviation of peak force and impulse (aggregate of the force-time curve) was significantly greater (?25%) for the lower limb than for the upper limb (p < .01). Contractions that involved 1 or 2 joints within a limb had similar variability. Therefore, the upper limb might have better control of force than the lower limb because of its extensive use in fine motor tasks in daily activities.     

Monocular and Binocular Vision in the Control of Goal-Directed Movement

In the present research the authors examined the time course of binocular integration in goal-directed aiming and grasping. With liquid-crystal goggles, the authors manipulated vision independently to the right and left eyes of 10 students during movement preparation and movement execution. Contrary to earlier findings reported in catching experiments (I. Olivier, D. J. Weeks, K. L. Ricker, J. Lyons, & D. Elliott, 1998), neither a temporal nor a spatial binocular advantage was obtained in 1 grasping and 2 aiming studies. That result suggests that, at least in some circumstances, monocular vision is sufficient for the precise control of limb movements. In a final aiming experiment involving 3-dimen- sional spatial variability and no trial-to-trial visual feedback about performance, binocular vision was associated with greater spatial accuracy. Binocular superiority appeared to be most pronounced when participants were unable to adjust their limb control strategy or procedure on the basis of terminal feedback about performance.     

Directional Variability of the Isometric Force Vector Produced by the Human Hand in Multijoint Planar Tasks

Numerous studies have examined control of force magnitude, but relatively little research has considered force direction control. The subjects applied isometric forces to a handle and the authors compared within-trial variability when force is produced in different directions. The standard deviation of the force parallel to the prescribed direction of force production increased linearly with the targeted force level, as did the standard deviation of the force perpendicular to the instructed direction. In contrast, the standard deviation of the angle of force production decreased with increased force level. In the 4 (of 8) instructed force directions where the endpoint force was generated due to a joint torque in only 1 joint (either the shoulder or elbow) the principal component axes in force space were well aligned with the prescribed direction of force production. In the other directions, the variance was approximately equal along the 2 force axes. The variance explained by the first principal component was significantly larger in torque space compared to the force space, and mostly corresponded to positive correlation between the joint torques. Such coordinated changes suggest that the torque variability was mainly due to the variability of the common drive to the muscles serving 2 joints, although this statement needs to be supported by direct studies of muscle activation in the future.     

Blocking in Rapid Finger Tapping: The Role of Variability in Proximodistal Coordination

In rapid finger tapping, occasional intertap intervals of about twice the normal length or even longer, called blockings, can be observed. Skilled rapid tapping requires that flexor and extensor activity be timed so that they coincide with certain phases of the finger movement. In the present study, the hypothesis examined was that blockings are associated with a deviation from the proper timing relations between the more proximal signals (electromyographic [EMG] bursts) and the more distal signal (position-time curve of the finger). Participants (N = 8) performed up-and-down tapping. Blockings were compared with the preceding normal tapping cycles; a temporal forward shift of the flexor burst in the time interval between two kinematic landmarks—the lifting of the finger and the reversal of the movement—was found consistently in the blockings The phase shift of the flexor burst relative to the kinematic landmarks did not develop gradually in the course of the tapping cycles that preceded the blocking but was an abrupt deviation, which suggests that blockings occur with an increased likelihood as the extremes of the normal variability of the phase relation are approached.     

A study of the greater male variability hypothesis in creative thinking in Mainland China: Male superiority exists

This study tested the greater male variability hypothesis in creative thinking with a Chinese student sample in Mainland China. The Test for Creative Thinking-Drawing Production (TCT-DP) was administered to 627 Chinese adolescent boys (n = 332) and girls (n = 295). Results using the boy/girl variance ratio (VR) generally supported the hypothesis that boys have greater variability than girls in creativity test performance. However, results using the boy/girl ratios from different regions of the creativity score distribution revealed a pattern of male superiority. While boys significantly outnumbered girls in the higher extremes, girls tended to outnumber boys in the central region and the lower extremes. Results from an analysis of the means lent further support to the findings of male superiority. Plausible explanations for greater male variability and male superiority in Mainland China are proposed. The theoretical and practical implications of the findings are discussed.     

Cognitive-emotional dysfunction among noisy minds: Predictions from individual differences in reaction time variability

Mental noise can be defined as less reliable information processing. Individuals with high levels of mental noise are thought to be disadvantaged in cognitive, emotional, and behavioural realms. The present five studies (total N=298) investigated such potential disadvantages among normally functioning college undergraduates. Mental noise was operationalised in terms of the reaction time coefficient of variation (RTCV), a measure of RT variability that corrects for average levels of mental speed. Individuals with higher RTCV exhibited less effective cognitive control (Studies 1 and 5), less controlled behaviour (Study 2), and were more prone to negative emotional experiences (Study 3) and depressive symptoms (Study 4). Study 5 extended these results and found that individuals higher (versus lower) in RTCV were more adversely affected by their attentional lapses in daily life. Results converge on the idea that mental noise is an important individual difference dimension with multiple adverse correlates and consequences.