Biasing the pacemaker in the behavioral theory of timing

In the behavioral theory of timing, pacemaker rate is determined by overall rate of reinforcement. A two-alternative free-operant psychophysical procedure was employed to investigate whether pacemaker period was also sensitive to the differential rate of reinforcement. Responding on a left key during the first 25 s and on a right key during the second 25 s of a 50-s trial was reinforced at variable intervals, and variable-interval schedule values during the two halves of the trials were varied systematically. Responding on the right key during the first 25 s and on the left key during the second 25 s was not reinforced. Estimates of pacemaker period were derived from fits of a function predicted by the behavioral theory of timing to right-key response proportions in consecutive 5-s bins of the 50-s trial. Estimates of pacemaker period were shortest when the differential reinforcer rate most strongly favored right-key responses, and were longest when the differential reinforcer rate most strongly favored left-key responses. The results were consistent with the conclusion that pacemaker rate is influenced by relative reinforcer rate.     

To pray or not to pray: Reflections on the intersection of prayer and medicine

Recent medical studies documenting the influence of prayer in our physical lives challenge mainstream Christians to rethink their ideas and practice of prayer. A new model of prayer questions dysfunctional images of prayer based on 1) the doctrine of divine omnipotence, 2) the rewards-punishments notion of health and illness, and 3) linear notions of the power of prayer. Relational, holistic, and multidimensional images of God, human existence, and the effects of prayer provide the basis for a constructive theology of prayer. Ironically, the fact that prayer is not omnipotent makes it possible to practice prayer in a technological context.     

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.     

Pronominalization and discourse coherence,discourse structure and pronoun interpretation

Two self-paced reading-time experiments are reported that examine the time course of pronoun interpretation processes based on local discourse structure and on world knowledge. The characterization of local discourse structure is based on recent work on centering, which provides a specific formulation of how the ways in which sentences make reference to common entities determines the coherence of discourse segments and how discourse structure influences interpretation of ambiguous pronouns. The results of the first experiment show that readers generate a default interpretation of a pronoun based on features of local discourse structure, and that that default interpretation is later confirmed or overridden by knowledge-based processes. The results of the second experiment show that local discourse structure continues to influence pronoun interpretation even when the semantic information that ultimately compels interpretation occurs before the pronoun. These results support the view that processes acting on local discourse structure play a powerful role in guiding language comprehension.     

Is space-time discrete or continuous? — An empirical question

In this paper I present the Discrete Space-Time Thesis, in a way which enables me to defend it against various well-known objections, and which extends to the discrete versions of Special and General Relativity with only minor difficulties. The point of this presentation is not to convince readers that space-time really is discrete but rather to convince them that we do not yet know whether or not it is. Having argued that it is an open question whether or not space-time is discrete, I then turn to some possible empirical evidence, which we do not yet have. This evidence is based on some slight differences between commonly occurring differential equations and their discrete analogs.I would like to express my thanks to John McKie with whom I have had several inspiring conversations about discrete space. I would also like to thank the audience of a paper on this topic which I read in October 1991 at the College Park campus of the University of Maryland. Finally I would like to thank the referees ofSynthese for their comments. One of them, in particular, should be thanked especially for help in improving Appendix Two.     

The third person effect: Social distance and perceived media bias

Two studies were conducted to determine the conditions under which the third person effect (Davison, 1983) operates. It was hypothesized that the effect would be accentuated as target groups of others became more remote from the self. A second objective was to determine whether the effect operates in the absence of overtly persuasive intent in the media. Television programmes concerned with moral themes were employed as stimuli. The results further support Davison's claim that overestimation of media effects is greater when people imagine the responses of others whom they do not know than those of familar individuals. The results also indicate that the third person effect does operate in the absence of perceived persuasive intent, but is accentuated when bias is perceived by viewers.