Achieving Coordination in Prehension: Joint Freezing and Postural Contributions

The focus of the present study was on the intersegmental relationships that emerge when both task and oganismic constraints are imposed upon the coordination system. Seven right-handed subjects were required to reach and grasp a cup (hand transport phase) and place it on a designated target (cup transport phase), using either their preferred or nonpreferred hand. The kinematics of the movement were examined as a function of task (grasping a full cup versus grasping an empty one) and organismic (preferred or nonpreferred hand) constraints. During the hand transport phase, a task constraint effect was revealed through an increase in the low-velocity phase for the full cup condition. This constraint coexisted with a decrease in angular motion of the shoulder and elbow joints, indicating subjects reduced the number of variables to be independently controlled in the final homing-in stage of the movement. Accompanying this decrease in angular change was an increase in the displacement of the trunk. During the cup transport phase, the trunk was shown to contribute significantly more to the movement in the full cup condition and for the left hand movements, thereby increasing the stability of the movement system. These findings are in agreement with Bernstein's (1967) notion of fixating parts of the body as an initial solution to a movement problem, and they lend support to the concept of a proximodistal organization of coordination.     

A Comparison of the Effectiveness of Substantive and Contextual Mediation Tactics1

The effectiveness of three mediation tactics was compared in two laboratory studies. It was hypothesized that a content mediation procedure which involved identifying the priorities of both parties and suggesting a trade-off of low for high priority issues would be most effective in helping to resolve the dispute, followed by an issue identification mediation procedure in which priorities were identified but no suggestions were made. A positive framing mediation procedure in which the benefits of a negotiated settlement were emphasized was expected to be somewhat less effective. In Study 1, 64 students played the role of company negotiator and interacted with a programmed citizen group negotiator. All three mediation tactics produced more satisfactory outcomes (higher joint payoffs) than did a no-mediation condition. In Study 2, 46 pairs of students negotiated with one another and received content mediation, issue identification mediation, positive framing mediation, or no mediation. Negotiators receiving content mediation achieved more satisfactory outcomes (higher joint profits) than did negotiators in the other 3 conditions. Results are discussed in terms of a contingency model of mediation effectiveness.     

Ethnic and Gender Variations in the Sources of Information Used to Evaluate Performance in the Exercise Setting1

The purpose of this study was to identify ethnic and gender differences in the types of information Anglo and Hispanic exercisers use in self-evaluation. University students in exercise classes rated the importance of norm-referenced and self-referenced sources used in self-evaluation of performance. Results showed that males rated norm-referenced sources as more important to self-evaluation, while females rated self-referenced sources as most important. A gender by ethnicity interaction showed that Anglos, especially Anglo males, preferred norm-referenced sources, while Hispanics preferred self-referenced sources. Provided with this information, instructors could more effectively motivate exercise participants.     

SUPERVISORY MENTORING BY ADVISERS: RELATIONSHIPS WITH DOCTORAL STUDENT POTENTIAL, PRODUCTIVITY, AND COMMITMENT

A 2-year, three-panel (T1-T3) longitudinal study of 233 entering Ph.D. students examined the relationships between student potential for mentoring, (i.e., attitudes and objective abilities at entry (T1), mentoring functions used by the faculty adviser (T2,T3), and student research productivity and commitment (T3). Student potential was found to predict the amount of psychosocial mentoring, career mentoring, and research collaboration provided by the adviser. Psychosocial mentoring and collaboration were not related to student productivity or commitment after controlling for the students' entering abilities and attitudes. Career mentoring at T2 was negatively related to the students' affective commitment to their program at T3. Implications for our understanding of mentoring and future research are discussed.     

Behavioral economics of concurrent ethanol-sucrose and sucrose reinforcement in the rat: effects of altering variable-ratio requirements.

These experiments examined the own-price and cross-price elasticities of a drug (ethanol mixed with 10% sucrose) and a nondrug (10% sucrose) reinforcer. Rats were presented with ethanol-sucrose and sucrose, both available on concurrent independent variable-ratio (VR) 8 schedules of reinforcement. In Experiment 1, the variable ratio for the ethanol mix was systematically raised to 10, 12, 14, 16, 20, and 30, while the variable ratio for sucrose remained at 8. Five of the 6 rats increased ethanol-reinforced responding at some of the increments and defended baseline levels of ethanol intake. However, the rats eventually ceased ethanol-reinforced responding at the highest variable ratios. Sucrose-reinforced responding was not systematically affected by the changes in variable ratio for ethanol mix. In Experiment 2, the variable ratio for sucrose was systematically increased while the ethanol-sucrose response requirement remained constant. The rats decreased sucrose-reinforced responding and increased ethanol-sucrose-reinforced responding, resulting in a two- to 10-fold increase in ethanol intake. Experiment 3 examined the substitutability of qualitatively identical reinforcers: 10% sucrose versus 10% sucrose. Increases in variable-ratio requirements at the preferred lever resulted in a switch in lever preference. Experiment 4 examined whether 10% ethanol mix substituted for 5% ethanol mix, with increasing variable-ratio requirements of the 5% ethanol. All rats eventually responded predominantly for the 10% ethanol mix, but total amount of ethanol consumed per session did not systematically change. In Experiment 5, the variable-ratio requirements for both ethanol and sucrose were simultaneously raised to VR 120; 7 of 8 rats increased ethanol-reinforced responding while decreasing sucrose-reinforced responding. These data suggest that, within this ethanol-induction procedure and within certain parameters, demand for ethanol-sucrose was relatively inelastic, and sucrose consumption was independent of ethanol-sucrose consumption. Demand for sucrose, on the other hand, was relatively elastic, and ethanol-sucrose readily substituted for it. The results are discussed in terms of applying a behavioral economic approach to relationships between drug and nondrug reinforcers.     

Public knowledge,attitudes, and beliefs about homeless people: Evidence for compassion fatigue?

Media reports suggest that the public is becoming impatient with the homeless—that so-called “compassion fatigue” has gripped the nation. This characterization of public sentiment could have important policy consequences—restrictive measures can be justified by growing public impatience, and progressive housing policies seem infeasible within a hostile climate of opinion. But evidence to support the compassion fatigue notion is anecdotal. We examine the issue by tracking the results of public opinion polls and by reporting detailed evidence from a nationwide random-digit dial telephone survey (N=1,507) concerning knowledge attitudes and beliefs about homeless people. To be sure, the public sees homelessness as an undesirable social problem and wants something done about it. However, although the homeless are clearly stigmatized, there is little evidence to suggest that the public has lost compassion and is unwilling to support policies to help homeless people.     

Perceptual scaling of synthesized musical timbres: Common dimensions,specificities, and latent subject classes

To study the perceptual structure of musical timbre and the effects of musical training, timbral dissimilarities of synthesized instrument sounds were rated by professional musicians, amateur musicians, and nonmusicians. The data were analyzed with an extended version of the multidimensional scaling algorithm CLASCAL (Winsberg & De Soete, 1993), which estimates the number of latent classes of subjects, the coordinates of each timbre on common Euclidean dimensions, a specificity value of unique attributes for each timbre, and a separate weight for each latent class on each of the common dimensions and the set of specificities. Five latent classes were found for a three-dimensional spatial model with specificities. Common dimensions were quantified psychophysically in terms of log-rise time, spectral centroid, and degree of spectral variation. The results further suggest that musical timbres possess specific attributes not accounted for by these shared perceptual dimensions. Weight patterns indicate that perceptual salience of dimensions and specificities varied across classes. A comparison of class structure with biographical factors associated with degree of musical training and activity was not clearly related to the class structure, though musicians gave more precise and coherent judgments than did nonmusicians or amateurs. The model with latent classes and specificities gave a better fit to the data and made the acoustic correlates of the common dimensions more interpretable.     

Applying market principles to the delivery of careers guidance services: A critical review

Market principles can be applied to careers guidance services through the concept of guidance as market-maker or through the concept of a market in guidance. The notion of a market in guidance can take the form of a real market or of a quasi-market. A quasi-market can take the form of contracts or of vouchers. These three sets of options are explored in relation to current policy developments in the careers guidance field.