Patterns of correlation between vehicle occupant seat pressure and anthropometry

Seat pressure is known as a major factor of seat comfort in vehicles. In passenger vehicles, there is lacking research into the seat comfort of rear seat occupants. As accurate seat pressure measurement requires significant effort, simulation of seat pressure is evolving as a preferred method. However, analytic methods are based on complex finite element modeling and therefore are time consuming and involve high investment. Based on accurate anthropometric measurements of 64 male subjects and outboard rear seat pressure measurements in three different passenger vehicles, this study investigates if a set of parameters derived from seat pressure mapping are sensitive enough to differentiate between different seats and whether they correlate with anthropometry in linear models. In addition to the pressure map analysis, H-Points were measured with a coordinate measurement system based on palpated body landmarks and the range of H-Point locations in the three seats is provided. It was found that for the cushion, cushion contact area and cushion front area/force could be modeled by subject anthropometry, while only seatback contact area could be modeled based on anthropometry for all three vehicles. Major differences were found between the vehicles for other parameters.     

Seat Biases in Proportional Representation Systems with Thresholds

In proportional representation systems, apportionment methods are used to convert the number of votes of a party into the number of seats allocated to this party. An interesting characteristic of any such method are the seat biases, that is, the expected differences between the actual seat allocation and the ideal share of seats, separately for each party, when parties are ordered from largest to smallest. For electoral systems with a threshold, that is, with a minimum percentage of votes that parties must reach in order to be eligible to participate in the apportionment process, we show that seat biases decrease from their maximum to zero, as the threshold increases from zero to its maximum, and that all seat biases decrease linearly.     

Candidate Sex and Congressional Elections

Abstract

In 1992, an unprecedented number of women were elected to Congress. This election seemed to debunk the notion of female disadvantage as female candidates ran better than males. Since 1992, however, female candidates have failed to compete as effectively as men in congressional elections, again raising the specter of a sex bias. In this paper, we examine 365 open seat congressional elections held since 1982 in order to ascertain whether the indicators of female success in the 1980s and early 1990s structured female candidate success and/or failure after 1992. For this study, these indicators include candidate attributes such as financial quality and candidate experience. Our examination indicates that candidate attributes have significantly weakened as predictors of open seat election outcomes, especially in female versus male races. Instead, a strong increase in the correlation of the presidential normal vote and the congressional vote in open seats since 1992 indicates the emergence of elections where candidate attributes are secondary to the partisanship of the district. Female versus male races demonstrate much higher partisan coherence than all-male open seat contests, and Democratic women run about six points behind Republican women when district partisanship is controlled. These factors, combined with the increasingly Democratic distribution of female nominations, mitigate against female gains through open seats after 1992.     

Three experiments to support the design of lightweight comfortable vehicle seats

Seats need to be more lightweight for airplanes, cars, busses and even trains to contribute to a better environment and to reduce energy consumption. However, a reduction in comfort due to weight reduction is not preferable, which opens a new area of research: improving comfort with a minimum of material or with lightweight materials and systems. In this paper three experiments are performed to test the effects of light weight seats and parts of a seat on comfort. The first experiment shows that a new developed light weight massage system improves comfort and reduces muscle activity. The second experiment shows that the automatic seat adjustment without motors improves the comfort as well. The third experiment showed that a light weight seat following closely the human body contour is experienced on many aspects in the same way as current more heavy seats. More research and models will be needed in this ergonomic field which needs more attention.     

Assessing manual lifting tasks based on segment angle interpolations

This study investigates the effects of the number of interpolation points on the prediction accuracy of segment angle trajectory during lifting. Ten participants performed various lifting tasks while a motion tracking system recorded their movements. Two-point through ten-point equal time-spaced segment angles extracted from major segment trajectory data captured by the motion tracking system were used to re-generate the whole body lifting motion by using polynomial and cubic spline interpolation methods. The root mean square error (RMSE) between the reference (motion tracking system) and the estimated (interpolation method) segment angle trajectories were calculated to quantify the prediction accuracy. The results showed that the cubic spline interpolation will yield a smaller RMSE value than one based on the polynomial interpolation. While increasing the number of interpolation points can reduce the RMSE of the estimated segment angle trajectories, there was a diminishing advantage in continuing to add interpolation points. A sensitivity analysis suggests that if the estimation of the segment angles at each interpolation point deviates considerably from the real value, and cannot be controlled at a low level (<10 (), the use of higher number of interpolation points will not improve the estimation accuracy.     

Reducing whole body vibration in forklift drivers

Forklift drivers in warehouses are often exposed to whole body vibration (WBV) during the total day. There is however an association between working as a forklift operator and the development of low back pain. In this study the exposure to WBV was measured in five forklift drivers who performed a standardised order picking task during 10 minutes. The effect of driving surface (uneven concrete vs. new flat concrete), driving speed (15 km/h vs. 8 km/h) and seat suspension (mechanical suspension vs. air suspension) was investigated. Improving the driving surface was the most effective preventive measure by reducing the whole body vibration with 39%, from 1.14 to 0.69 m/s2. Lowering the speed limit resulted in a reduction of WBV with 26% (1.05 vs. 0.78 m/s2). An air suspension seat was 22% more effective compared to mechanical suspension (1.02 vs. 0.80 m/s2). On uneven concrete an air suspension seat performed even better by reducing the WBV by 29% (1.33 vs. 0.95 m/s2). A combination of a new driving surface, limiting the maximum speed and the introduction of an air suspension seat reduced the whole body vibrations below the action limit of 0.5 m/s2 as mentioned in the European directive. None of the interventions were effective enough on their own.     

Effects of Posture on Newborn Crying

Acoustic properties of the cries of 14 infants were evaluated at both 2 and 4 weeks of age when the infants were lying in a supine position and when they were sitting upright in a car seat. In the upright position, infants' breathing was more rapid and showed less individual variability. The fundamental frequency of their cries increased in the upright position, but this increase was likely attributable to increased arousal or distress, not to posture per se. There were no differences in acoustic measures related to vocal tract shape in the supine versus upright positions. Across age, there was a decline in fundamental frequency. Individual difference stability of most acoustic measures was moderate to high. The importance of postural effects on the acoustic features of cries was discussed.     

Ergonomic evaluation of laparoendoscopic single-site surgery ports in a validated laparoscopic training model

Although laparoendoscopic single-site surgery (LESS) is feasible among expert laparoscopic surgeons, it poses many technical challenges not seen in conventional laparoscopy (CL). Recent technological advancements in single-incision instrumentation have created more interest and widespread usage of LESS. However, neither LESS nor its novel instrumentation have been thoroughly studied or evaluated using human factors and ergonomics techniques. Consequently, the aim of this study was to compare the physical performance of LESS to CL using a standardized task. Wrist and elbow angular movements, range of motion and physical discomfort were assessed for 24 novice participants. There were no significant differences for physical comfort/discomfort ratings or elbow and wrist flexion/extension range of motion between CL and LESS. However, wrist radial/ulnar range of motion was significantly greater in LESS compared to CL (p < 0.05). Additionally, wrist radial/ ulnar range of motion was significantly greater using the SILS Port compared to the GelPOINT (p < 0.05). Although further investigation is needed, LESS resulted in greater wrist deviation and range of motion due to the close proximity of the instruments, restrictive nature of the single-port devices, and the need to achieve adequate instrument triangulation and visualization.     

Bivariate pointing movements on large touch screens: investigating the validity of a refined Fitts' Law

On the basis of three empirical studies Fitts' Law was refined for bivariate pointing tasks on large touch screens. In the first study different target width parameters were investigated. The second study considered the effect of the motion angle. Based on the results of the two studies a refined model for movement time in human-computer interaction was formulated. A third study, which is described here in detail, concerns the validation of the refined model. For the validation study 20 subjects had to execute a bivariate pointing task on a large touch screen. In the experimental task 250 rectangular target objects were displayed at a randomly chosen position on the screen covering a broad range of ID values (ID= [1.01; 4.88]). Compared to existing refinements of Fitts' Law, the new model shows highest predictive validity. A promising field of application of the model is the ergonomic design and evaluation of project management software. By using the refined model, software designers can calculate a priori the appropriate angular position and the size of buttons, menus or icons.     

The effect of task differences,attention and personality on the frequency of body-focused hand movements

A hypothesized relationship between apparently irrelevant self or object manipulatory hand movements and attentional demand was investigated by observing the frequency of these hand movements during the performance of three tasks: a monologue, mental arithmetic, and rest. The attentional demand of each task was assessed by means of a simultaneous reaction time probe task. The monologue task had both the highest frequency of hand movements and the highest level of attentional demand. However, correlations between these measures were not significant for any of the tasks. The influence of the task differences on movement frequencies was much greater than the effect of individual differences. Correlations of trait anxiety and field dependence measures with movement frequencies varied markedly with task differences. The nature and significance of these movements is considered by reference to similar observations in nonhuman species.     

The relationship between explicit and implicit learning processes and probable pathological gambling

This paper reports the findings of a study of explicit and implicit learning and gambling with non-problem (n = 107), sub-clinical problem gamblers (n = 13), and probable pathological gamblers (n = 46). Two probability learning tasks modeled after gambling games and an artificial grammar task were used to explore how people learn patterns. In each of the two probability learning tasks, the outcome of the game was biased during the first part (learning phase) of the task. The results showed that many of the participants in the experimental conditions learned the bias and gradually unlearned the bias during the extinction phase of the study. Probable pathological gamblers showed less retention of the bias during two probability tasks and repeated the same errors during the artificial grammar task suggesting that they emphasize explicit learning strategies rather than implicit learning strategies. The results are consistent with the idea that pathological gamblers are more likely to utilize explicit rules than implicit rules.     

Overconfidence in absolute and relative performance: The regression hypothesis and Bayesian updating

Studies have found that people are overconfident in estimation involving difficult tasks but underconfident in easy tasks. Conversely, they are overconfident in placing themselves in easy tasks but underconfident in hard tasks. These findings can be explained by a regression hypothesis that implies random errors in estimation as well as by rational Bayesian updating (that implies no random error). We test these hypotheses in five experiments. We find overconfidence in estimation involving hard tasks but underconfidence in easy tasks. However, for placement (involving both easy and hard tasks) we find no overconfidence, regression effects due to low and high anchor points, and extreme underconfidence when people choose between multiple alternatives. On the other hand, when given precise information about absolute performance, people’s re-assessments of relative performance are consistent with the Bayesian model. Since placement judgments are important in many competitive settings, our results emphasize the need for more research to identify their determinants.     

Concurrent cognitive task may improve motor work performance and reduce muscle fatigue

Performance of certain cognitive tasks either during physical load or in rest pauses between boosts might lead to slowing of muscle fatigue and fatigue related decline in performance. Seventeen right-handed healthy volunteers (age 24 ± 1.4, 8 males) participated in this study, aiming to investigate the effect of the level of the cognitive information processing - 1) passive perception of audio stimuli, 2) active stimuli discrimination, 3) active stimuli discrimination following motor response - on motor task performance (handgrip test 30% and 7% of MVC) and muscle fatigue development. Cognitive tasks show the following effects on motor work: i) Perceived fatigue during 30 % MVC (fatiguing) condition developed slower if participant pressed button in response to deviant acoustic stimuli, as compared to passive listening. Counting task, an active task without motor component, took the intermediate position and did not differ significantly from two other cognitive tasks. ii) MVC after 30% MVC (fatiguing) condition tended to decrease stronger when accompanied with passive listening in comparison with both active tasks. iii) Motor task performance during 30% MVC (fatiguing) condition was better for active cognitive task with motor component than for passive task. Active task without motor component took the intermediate position and did not differ significantly from both the other cognitive tasks.     

Certificates of optimality: the third way to biproportional apportionment

The biproportional apportionment problem (BAP) must be faced in many proportional electoral systems where seats must be allocated to parties within regions. BAP is a non-trivial optimization problem, and only sophisticated algorithms are currently available for solving it. The issue is: are they “writable” as an actual law? Citizens rightly demand simple, easy to understand, voting systems. The alternative, though, seems to have simple, but unsound electoral laws. We propose the following way out of this dilemma: leave to a mathematically sophisticated algorithm the task of producing an optimal apportionment, but attach to it a “certificate of optimality”, that is, describe a simple procedure whereby anybody can check, through some elementary operations, that the seat allocation output by the algorithm is indeed an optimal apportionment. We discuss one such certificate, based on the Max flow- min cut Theorem, relative to a parametric max flow method of ours for BAP.     

Adolescents' Emotional Experiences of Mother–Adolescent Conflict Predict Internalizing and Externalizing Symptoms

Research on adolescent emotion has generally focused on expressions of emotion; however, there are reasons to believe that adolescents' experiences of emotion may be related to adolescent development in unique and important ways. This study examined the relation of adolescents' emotional experiences of conflict with their mothers to their internalizing and externalizing symptoms at three time points, each a year apart. After participating in videotaped conflict negotiation tasks with their mothers, adolescents (N=80) watched the videotape of their interactions and used a joystick to make continuous ratings of how negative, positive, or neutral they felt during the discussions. Hierarchical Linear Modeling was used to assess relations among their continuous emotion ratings and their internalizing and externalizing symptoms 1 year before the interaction task, at the time of the interaction task, and 1 year later. Adolescents' externalizing symptoms at the time of the conflict task were associated with negative emotion that decreased across the conflict discussion. Relations between emotional experience and internalizing symptoms a year later were moderated by adolescent gender, revealing that a tolerance for increasing negative emotion predicts fewer future internalizing symptoms for girls. The importance of adolescents' ability to tolerate negative emotion during normal developmental conflicts is discussed.     

Analyzing Web pages visual scanpaths: between and within tasks variability

In this paper, we propose a new method for comparing scanpaths in a bottom-up approach, and a test of the scanpath theory. To do so, we conducted a laboratory experiment in which 113 participants were invited to accomplish a set of tasks on two different websites. For each site, they had to perform two tasks that had to be repeated ounce. The data were analyzed using a procedure similar to the one used by Duchowski et al. [8]. The first step was to automatically identify, then label, AOIs with the mean-shift clustering procedure [19]. Then, scanpaths were compared two by two with a modified version of the string-edit method, which take into account the order of AOIs visualizations [2]. Our results show that scanpaths variability between tasks but within participants seems to be lower than the variability within task for a given participant. In other words participants seem to be more coherent when they perform different tasks, than when they repeat the same tasks. In addition, participants view more of the same AOI when they perform a different task on the same Web page than when they repeated the same task. These results are quite different from what predicts the scanpath theory.     

Infant Distress and Regulatory Behaviors Vary as a Function of Attachment Security Regardless of Emotion Context and Maternal Involvement

Differences in infant distress and regulatory behaviors based on the quality of attachment to mother, emotion context (frustration versus fear), and whether or not mothers were actively involved in the emotion-eliciting tasks were examined in a sample of 98 16-month-old infants and their mothers. Dyads participated in the Strange Situation, a limiting task designed to elicit infant frustration, and a novelty task designed to elicit infant fear. Mothers were asked to remain uninvolved during the first minute of each task, and then instructed to engage with their infants as they wished for the remaining three minutes. Independent of concurrent maternal sensitivity, resistant infants were significantly more distressed than secure and avoidant infants. Avoidant infants engaged in fewer active mother-oriented regulation behaviors than secure and resistant infants and engaged in more self-soothing in the mother involved condition than the mother uninvolved condition. Resistant infants engaged in more physical comfort with their mothers and more venting than both secure and avoidant infants, and exhibited a smaller variety of adaptive non-mother-oriented strategies than did secure infants. There were few differences in infant distress and regulatory behaviors as a function of emotion task and maternal involvement. Limitations and implications for future research are discussed.     

The Effects of Distraction on Cognitive Task Performance During Toddlerhood

We investigated the effects of distraction on attention and task performance during toddlerhood. Thirty toddlers (24‐ to 26‐month‐olds) completed different tasks (2 of each: categorization, problem solving, memory, free play) in one of two conditions: No Distraction or Distraction. The results revealed that the distractor had varying effects on performance scores depending on the task: The problem solving and memory tasks were more susceptible to distraction. In addition, the two conditions showed different patterns of attention over time. Toddlers in the No Distraction condition were more attentive, and their attention remained consistently high across the session. Toddlers in the Distraction condition increased their attention to the task and decreased their attention to the distractor in the second half of the session. This study demonstrates how the presence of distraction influences toddlers’ performance on individual cognitive tasks and contributes to our understanding of distractibility and endogenous attention during toddlerhood. This work also has implications for how environmental noise, such as background television, may influence cognitive development.     

Brain Electrical Activity Associated With Cognitive Processing During a Looking Version of the A‐Not‐B Task

This work was designed to investigate individual differences in brain electrical activity during a looking version of the A‐not‐B task. It was proposed that this spatial task required the cognitive skills of working memory and inhibitory control, each associated with frontal lobe function. Electroencephalograms (EEGs) were recorded from 54 8‐month‐old infants during baseline and task. Only high performers on the looking task exhibited increases in 6‐ to 9‐Hz EEG power from baseline to task. These task‐related changes were evident at frontal and posterior scalp locations. High performers on the looking task exhibited lower EEG coherence values at right hemisphere frontal locations relative to the low performers. These lower coherence values were evident during baseline and task. All infants showed increased frontal‐parietal coherence during the spatial working memory task relative to baseline values. These data confirm previous cognitive neuroscience work associating frontal lobe function with cognitive performance levels during infancy.