After-effects of using a weighted bat on subsequent swing velocity and batters' perceptions of swing velocity and heaviness

In baseball and softball, warm-up swings with a weighted bat have been believed to increase swing velocity when an ordinary bat is used in the subsequent competitive situation. The purpose of this study was to investigate the after-effects of using a weighted bat on subsequent swing velocity and batters' perceptions of swing velocity and heaviness. Eight men in varsity softball and baseball hit a ball suspended from the ceiling 45 times (3 sets of 15 trials). For each set, the initial 5 trials were done using an ordinary 920-g wooden bat (Control condition), and the following 5 trials by a bat with an 800-g bat ring (Weighted condition), and the final 5 trials again by the ordinary bat (post-Weighted condition). Analysis of variance showed a significant decrease of 3.3% in the measured linear velocity of the bat prior to impact with the ball for the first swing of the post-Weighted condition compared with the Control condition. From the second swing the velocity returned to the level of the Control condition. Subjective judgment of the heaviness and velocity of swings for the Weighted and post-Weighted conditions by each participant showed that the ordinary bat felt lighter and swing speed felt faster for the post-Weighted condition. The advantage of the warm-up with a weighted bat was thus psychological and not biomechanical.     

Prospective dynamic balance control during the swing phase of walking: Stability boundaries and time-to-contact analysis

This study examined the prospective control of the swing phase in young healthy adults while walking at preferred speed over unobstructed ground and during obstacle clearance. Three aspects of swing were examined: (1) the relation of the body Center of Mass (CoM) to the stability boundaries at the base of support; (2) a dynamic time-to-contact analysis of the CoM and swing foot to these boundaries; and (3) the role of head movements in the prospective control of gait and field of view assessment. The time-to-contact analysis of CoM and swing foot showed less stable swing dynamics in the trail foot compared to the lead foot in the approach to the unstable equilibrium, with the CoM leading the swing foot and crossing the anterior stability boundary before the swing foot. Compensations in temporal coupling occurred in the trail limb during the late swing phase. Time-to-contact analysis of head movement showed stronger prospective control of the lead foot, while fixation of the field of view occurred earlier in swing and was closer to the body in the obstacle condition compared to unobstructed walking. The dynamic time-to-contact analysis offers a new approach to assessing the unstable swing phase of walking in different populations.     

记叙文中因果连贯对空间情境模型回溯建构的促进

采用移动窗口阅读技术探讨记叙文理解中因果关系对于空间信息加工的作用。实验1和2的自变量是故事中空间信息与故事结果的因果关系,采用相关样本t检验对不同条件下探测词的反应时进行统计分析,结果表明因果关系不仅会影响文本明确提及的空间信息的加工而且能够促进隐含的空间关系建构情境模型。实验3的自变量是故事中物体与位置词的空间关系,采用相关样本t检验对不同条件下位置探测词的反应时进行统计分析,结果进一步表明空间情境模型是读者为保持故事因果连贯回溯建构的而不是在阅读进程中的实时建构。实验4中空间关系的复杂程度增大,结果发现当故事中空间信息的文本距离较远时即使有保持因果连贯的需要,读者仍无法回溯建构空间模型。     

Age differences in peripheral perceptual processing: a monoptic backward masking investigation

Peripheral processes in vision were investigated in two experiments involving monoptic backward masking with random noise. For young and old subjects, peripheral processing time (represented by stimulus onset asynchrony of target and mask) was characterized as a power function of target energy. Although processing time for both age groups showed a similar rate of decline with increasing target energy, old subjects processed targets more slowly at all energy levels. Results were independent of education, sex, and criterion differences between young and old. Target duration was related to critical interstimulus interval, such that stimulus onset asynchrony between target and mask was approximately constant for a given target energy within each age group. Evidence suggests that peripheral processing begins with target onset and that processing time is best characterized by a power function relating stimulus onset asynchrony of target and mask to target energy.     

Changing internal constraints on action: the role of backward inhibition

Flexible control of action requires the ability to disengage from previous goals or task sets. The authors tested the hypothesis that disengagement during intentional shifts between task sets is accompanied by inhibition of the previous task set ("backward inhibition"). As an expression of backward inhibition the authors predicted increased response times when shifting to a task set that had to be abandoned recently and, thus, suffers residual inhibition. The critical backward inhibition effect on the level of abstractly defined perceptual task sets was obtained across 6 different experiments. In addition, it was shown that backward inhibition can be differentiated from negative priming (Experiment 2), that it is tied to top-down sequential control (Experiment 3), that it can account at least partially for "residual shift costs" in set-shifting experiments (Experiment 4), and that it occurs even in the context of preplanned sequences of task sets (Experiment 5).     

Intelligence and information processing during an auditory discrimination task with backward masking: an event-related potential analysis

The relation between mental ability and auditory discrimination ability was examined by recording event-related potentials from 60 women during an auditory oddball task with backward masking. Across conditions that varied in intensity and in the interval between the target and masking stimuli, the higher ability (HA) group exhibited greater response accuracy, shorter response times, larger P3 amplitude, and shorter P3 latency to target stimuli than the lower ability (LA) group. When instructed to ignore the stimuli, the HA group exhibited shorter mismatch negativity latency to deviant tones than the LA group. The greater speed and accuracy of auditory discrimination for the HA group, observed here with multiple measures, is not a consequence of response strategy, test-taking ability, or attention deployment.     

Design and efficacy of a head-coil bite bar for reducing movement-related artifacts during functional MRI scanning

This article describes the design, construction, application, and effectiveness of a simple bite bar for use with an MRI whole-head coil to reduce head-movement-related artifacts during functional brain imaging. The device is comfortable to use and allows considerable flexibility in positioning the subject’s head. Eleven subjects were scanned while performing a motor-sequencing experiment with and without the bite bar. The bite bar was generally effective in reducing maximum head movement to less than 0.5 mm (translation) and 0.5° (rotation).     

Auditory backward recognition masking: effect of interaural phase on masker efficacy

The effect of interaural phase on pitch and lateralization recognition was examined. Tonal signals were followed by a variable interstimulus interval and an interference tone. Stimuli were presented in a binaural masking-level difference paradigm as a means of manipulating the perceptual location of the signal within the head. In separate tasks, subjects were required to recognize the pitch or location of the signal. The pitch-recognition task resulted in the expected increase in performance as the interstimulus interval increased. There was no effect of interaural phase on pitch-recognition performance. There was no significant effect of interstimulus interval on performance in location recognition. Subjects were proficient at recognizing location of the signal regardless of the interstimulus interval. The data suggest that a strict single-channel interpretation of the preperceptual storage model of backward auditory recognition is inadequate.     

An analysis of a contingency program on designated drivers at a college bar

The present study evaluated the effects of prompts and incentives on designated drivers in a bar. We defined the dependent variable as the percentage of customers either functioning as or riding with a designated driver. We used an ABCA design to evaluate the effectiveness of prompts and incentives on the dependent variable. Results indicated that the intervention was successful at increasing the ratio of safe to unsafe passengers in a bar.     

Applying an active lumbopelvic control strategy during lumbar extension exercises: Effect on muscle recruitment patterns of the lumbopelvic region

ObjectiveExamine whether implementing an active lumbopelvic control strategy during high load prone lumbar extension exercises affects posterior extensor chain recruitment and lumbopelvic kinematics.MethodsThirteen healthy adults acquired an optimal active lumbopelvic control strategy during guided/home-based training sessions. During the experimental session electromyography was used to evaluate the activity of the posterior extensor chain muscles during high load trunk/bilateral leg extension exercises with/without application of the strategy. Video-analysis was used to evaluate thoracic/lumbar/hip angles.ResultsImplementing the active lumbopelvic control strategy decreased the lordotic angle during trunk (p = 0.045; −3.2°) and leg extension exercises (p = 0.019; −10°). The hip angle was solely affected during trunk extension (p < 0.001; +9.2°). The posterior extensor chain (i.e. mean of the relative activity of all muscles (%MVIC) was recruited to a higher extent (p = 0.026; +9%) during trunk extension exercises performed with active lumbopelvic control. Applying the strategy during leg extension exercises lead to less activity of longissimus thoracic (p = 0.015; −10.2%) and latissimus dorsi (p = 0.010; −4.4%), and increased gluteus maximus activity (p ≤ 0.001; +16.8%).ConclusionsWhen healthy people are taught/instructed to apply an active lumbopelvic control strategy, this will decrease the degree of lumbar (hyper)lordosis and this influences the recruitment patterns of trunk and hip extensors. Hence, the possible impact on predetermined training goals should be taken into account by trainers.     

Influences of elbow,shoulder, trunk motion and temporospatial parameters on arm swing asymmetry of Parkinson's disease during walking

Arm swing asymmetry is commonly observed in early Parkinson's disease (PD) and has been found to be useful for early diagnosis. However, there are uncertainties about the nature of its relationships with gait parameters, especially shoulder and elbow motions. Therefore, this study explored how these relationships are different between PD and controls. Forty one early PD and 23 controls were included. Participants walked at self-selected speed for 3D motion analysis. Arm swing at the wrist (AS), temporospatial parameters and kinematics in elbow, shoulder and trunk were obtained. Amplitudes and asymmetries of these variables were compared between PD and control groups. PD group showed increased AS asymmetry, compared to controls. Multiple hierarchical regression analysis on AS asymmetry was conducted in order to investigate how PD influences on the relationship between AS asymmetry and other variables. In pooled data (PD and control group), asymmetries in elbow and shoulder range of motion (RoM) were significant predictors for AS asymmetry but walking speed and asymmetries in temporospatial parameters were not significant. Group effect (PD effect) was significantly mediated by only elbow RoM asymmetry. Interaction between group and elbow RoM asymmetry was statistically significant, indicating that group was an effect modifier for elbow RoM asymmetry effect on AS asymmetry. Conclusively, arm swing asymmetry measured at the wrist represents the involvement of PD effect on the unilateral and distal upper limb in early stage. These findings are helpful for future researches related to clinical applications and mechanisms of arm swing asymmetry in PD.     

Dialogue and power: a critical analysis of power in dialogical therapy

This article explores the relationship between dialogue and power in the practice of dialogue-oriented, "not-knowing" forms of therapy. It is argued that power of a dynamic and reversible kind infuses much ordinary social dialogue, and that the joint processes of power and resistance work together to render an interaction dialogical. In contrast, in dialogical therapy, overt exercises of power threaten the interaction's dialogical status, and power is deferred and denied by the therapist through not-knowing practices. A case study of Harlene Anderson's (1997) is used to illustrate that it is precisely power's presence that informs the practices of not knowing and uncertainty that characterize dialogical therapies. It is suggested that the not-knowing therapist withholds aspects of his or her voice as a condition for dialogicity. Instead, special speaking arrangements are required, in which the therapist's not-knowing is continuously communicated to the client, for the therapeutic conversation to remain dialogical. Without these speaking arrangements, I argue that therapy moves toward monologue. Therapists inherit powerful speaking positions from the institutional and sociocultural context, and the rejection of power within therapy serves only to conceal this aspect of power, which nevertheless pervades the therapeutic relationship. Finally, it is suggested that power is a "common factor"--shared by all therapies--and that our status as "inheritors" of power needs to be included in our understanding of the therapeutic process. This expanded view of therapy requires the re-theorization of dialogue, such that it includes, rather than excludes, considerations of power.     

Maternal behaviors and cognitions during discipline episodes: a comparison of power bouts and single acts of noncompliance

Maternal behaviors and cognitions within power bouts and single acts of noncompliance were compared by using 2 methodologies. Ninety mothers completed daily telephone interviews concerning their children's misbehavior for 12 days. Half of the mothers also completed a computerized simulation of 3 different power bouts, and the other half of the mothers completed a similar simulation of 3 sets of single noncompliance episodes. Mothers made behavioral intention choices and rated their perceptions of the child's behavior in the computer simulation. Results indicate that power bouts formed a special class of discipline episodes distinct from single noncompliance. Mothers reported more negative perceptions of the child as well as more aversion during extended power bouts. Discussion focuses on possible different types of power bouts and the need for theories of socialization to include the transactive nature of discipline episodes.