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.     

Validation of a full body 3-D dynamic linked segment model

In studies related to human movement, linked segment models (LSM's) are often used to quantify forces and torques, generated in body joints. Some LSM's represent only a few body segments. Others, for instance used in studies on the control of whole body movements, include all body segments. As a consequence of the complexity of 3-dimensional (3-D) analyses, most LSM's are restricted to one plane of motion. However, in asymmetric movements this may result in a loss of relevant information. The aim of the current study was to develop and validate a 3-D LSM including all body segments. Braces with markers, attached to all body segments, were used to record the body movements. The validation of the model was accomplished by comparing the measured with the estimated ground reaction force and by comparing the torques at the lumbo-sacral joint that resulted from a bottom-up and a top-down mechanical analysis. For both comparisons, reasonable to good agreement was found. Sources of error that could not be analysed this way, were subjected to an additional sensitivity analysis. It was concluded that the internal validity of the current model is quite satisfactory.     

Teacher stress and guidance work in Hong Kong secondary school teachers

Major sources of stress in Hong Kong teachers were investigated, with specific reference to guidance work as a potential source of stress. A survey of 415 secondary school teachers revealed that guidance-related aspects of work constituted a major dimension of stress, with guidance teachers, female teachers, younger teachers and junior teachers perceiving more stress than their counterparts in this dimension. Workload and time pressure were perceived as the most stressful aspects of work for all teachers. Results also showed an association between stress and job satisfaction, and biographical variables. Implications of the findings for teachers doing guidance work in Hong Kong and internationally are discussed.     

Short term Memory Impairment and Arithmetical Ability

We document the dissociation of preserved calculation skills in a patient with impaired auditory short-term memory. The patient (MRF) had a memory span of three digits. Furthermore, he showed rapid decrement in performance of single digits and letters with both auditory and visual presentation in the Brown-Peterson forgetting task. Analysis of his calculation skills revealed a normal ability to solve auditorily presented multidigit addition and subtraction problems such as 173 + 68 and to execute the Paced Auditory Serial Addition Task (Sampson, 1956, 1958; Gronwall, 1977). In addition, his performance on other tests, including arithmetic manipulation of natural numbers, decimals and fractions, approximation, magnitude, ratio, and percentage, appeared to be normal (Hitch, 1978b). It is argued that these findings require a revision of Baddeley and Hitch's (1974) concept of the function of working memory.     

Cultural specificity of support sources,correlates and contexts: Three studies of African-American and Caucasian youth

Levels and correlates of parental support, peer support, partner support, and/or spiritual support among African American and Caucasian youth were examined in three contexts: adolescent pregnancy (Study 1), first year of college (Study 2), and adolescence and young adulthood (ages 15–29; Study 3). Partially consistent with a cultural specificity perspective, in different contexts different support sources were higher in level and/or more strongly related to adjustment for one ethnic group than the other. Among pregnant adolescents, levels of spiritual support were higher for African Americans than Caucasians; additionally, peer support was positively related to well-being only for African Americans whereas partner support was positively related to well-being only for Caucasians. Among college freshmen, family support was more strongly related to institutional and goal commitment for African Americans than Caucasians; conversely, peer support was more strongly related to institutional and goal commitment among Caucasians. Among 15 to 29-year-olds, levels of parental support and spiritual support were higher among African Americans than Caucasians; additionally, spiritual support was positively related to self-esteem for African Americans but not for Caucasians. Implications and limitations of the research are discussed. The third study was supported by National Institute of Mental Health Grant RO1 MH40963. We thank Monica Greene, Shea Lyda, Wendy Stevenson, and the many undergraduate students who contributed to the three research projects. We also acknowledge the very thoughtful and helpful comments of the anonymous reviewers and the editor, Edison Trickett.     

Empirical study of the Americans with Disabilities Act: employment issues from 1990 to 1994

The Americans with Disabilities Act (ADA) of 1990 is the most comprehensive federal civil rights law addressing discrimination against one-fifth of the American population. This article is meant to contribute to the emerging dialogue on ADA implementation by presenting information from a longitudinal investigation of employment integration and economic opportunity under the employment provisions of the ADA, set forth in Title I of the act. The broader relevance of the investigation to emerging questions under Title I law is described. Thereafter, the investigation's seven core findings are presented, and then the implications for future investigation of the ADA are examined.     

Media use and political commitment: The 1992 U.S. presidential election

This study explores the relationship between media use and political commitment. Undergraduate participants answered an extensive political background questionnaire, which included measures of media use, perceived importance of information sources regarding the 1992 presidential election, and various political behaviors as an index of political commitment. Correlational analyses revealed that those who are more politically committed tend to select a variety of media sources regarding a presidential candidate. This study also investigated how informational and commitment variables were related to attitudes towards the major presidential candidates. Results observed for people expressing positive attitudes toward Perot are discussed in terms of the modern day “third party voter.”     

Influence of a Cross-Cultural Training Course on Racial Identity Attitudes of White Women and Men: Preliminary Perspectives

The authors examine the influence of cross-cultural training on the racial identity attitudes of 35 White graduate counselors in training (10 men and 25 women) and the impact of gender on training. A pretest-posttest comparison of responses to the White Racial Identity Attitudes Survey (WRIAS) was used. Results indicated that the cross-cultural training course (a) influenced racial identity attitudes of White counselors in training and (b) racial identity attitudes were influenced by gender.     

Comparing Risky Decision Making Under Conditions of Real and Hypothetical Consequences

In a series of three experiments, subjects made risky decisions under conditions of hypothetical or real consequences. Task variations across experiments included: (1) type of risk (monetary gambles or investments of time and effort), (2) within-subject and between-subjects manipulations of consequence condition, and (3) single or multiple decisions. The hypothesis of no difference between choices in real and hypothetical consequence conditions was retained in each experiment. Supplemental analyses ruled out various “artifactual” interpretations of the null results. Discussion focused on conditions in which researchers can and cannot infer decision makers’ actual risk preferences from their responses in laboratory tasks.     

Event-related brain potentials elicited by rhyming and non-rhyming pictures differentiate subgroups of reading disabled adolescents

Event-related brain potentials were recorded while disabled adolescent subjects read and judged whether two sequentially presented pictures had names that rhymed. Subjects with relatively good phonetic skills displayed an N400 priming effect, i.e., a significant reduction in the amplitude of the negative peak, occurring approximately 400 msec post-stimulus, for pictures with names that rhymed with preceding pictures as compared with pictures that had names that did not rhyme with the prime. No such effect was evident for subjects with relatively poor phonetic skills. This lack of an N400 priming effect provides evidence for a reduction in neural capacity and/or activation during phonological processing in the subjects with poor phonological skills. Demonstrating the N400 priming effect to be stronger in one group of reading disabled subjects, compared to another, supports the position that specific subtypes of reading disability exist. In addition to the stronger N400 priming effect, the phonetically stronger group also exhibited an enhanced negativity, from 700 to 1,000 msec after target stimulus onset, compared to phonetically inferior subjects. This finding replicates earlier work and possibly reflects a higher level of confidence in the group with better phonetic skills.