Can the Transition To and From Running and the Metabolic Cost of Running Be Determined From the Kinetic Energy of Running?

An experiment was conducted in which volume of used oxygen per stride time and the total segmental changes in kinetic energy generated per stride time, &grD;E(k)>s(-1), of 11 participants were determined on Day 1 for 7 treadmill running speeds. Gait transition speeds were determined on Day 2. Running metabolism and transition speed were predicted from the Day 1 mechanics of running expressed in Speed x &grD;E(k)>s(-1) coordinates. Predictions followed from the relation between 2 generalized quality ratios Q(metab), and Q(mech), with numerator &grD;E(k)>s(-1). In Q(metab), the denominator was the volume of used oxygen per stride time; in Q(mech), the denominator was the absolute regression constant from the linear dependency of &grD;E(k)>s(-1) on speed.     

The effects of token reinforcement,feedback and response cost on standardized test performance

The primary purpose of the present study was to compare the differential effects of token reinforcement, feedback, and response cost on the test performance of delinquent boys. Eighty students were randomly assigned to three experimental groups and one control group of 20 subjects each. Each experimental group received a standard and a modified administration of the verbal section of the WISC. For the token reinforcement group, the modified WISC administration permitted students to earn tokens contingent on correct responses; the response cost group forfeited tokens contingent on incorrect responses; and the feedback group simply received information regarding the accuracy of each response. The control group received two standard WISC administrations. The primary measure was the difference in verbal I.Q. scores between the standard and modified WISC administrations. Results indicated that the token reinforcement and response cost groups achieved significantly higher scores than the feedback and control groups. No significant differences were found between the token reinforcement and response cost groups nor between the feedback and control groups. The implications of these findings for clarifying the relationship between motivational condition and test performance are discussed.     

Patterns of human interlimb coordination emerge from the properties of non-linear, limit cycle oscillatory processes: theory and data

The present article represents an initial attempt to offer a principled solution to a fundamental problem of movement identified by Bernstein (1967), namely, how the degrees of freedom of the motor system are regulated. Conventional views of movement control focus on motor programs or closed-loop devices and have little or nothing to say on this matter. As an appropriate conceptual framework we offer Iberall and his colleagues' physical theory of homeokinetics first elaborated for movement by Kugler, Kelso, and Turvey (1980). Homeo kinetic theory characterizes biological systems as ensembles of non-linear, limit cycle oscillatory processes couple and mutually entrained at all the levels of organization. Patterns of interlimb coordination may be predicted from the properties of non-linear, limit cycle oscillators. In a set of experiments and formal demonstrations we show that cyclical, two-handed movements maintain fixed amplitude and frequency ( a stable limit cycle organization) under the following conditions: (a) when brief and constantly applied load perturbations are imposed on one hand or the other, (b) regardless of the presence or absence of fixed mechanical constraints, and (c) in the face of a range of external driving frequencies from a visual source. In addition, we observe a tight phasic relationship between the hands before and after perturbations (quantified by cross-correlation techniques), a tendency of one limb to entrain the other (mutual entrainment) and that limbs cycling at different frequencies reveal non-arbitrary, sub-harmonic relationships (small integer, subharmonic entrainment). In short, all the above patterns of interlimb coordination fall out of a non-linear oscillatory design. Discussion focuses on the compatibility of these results with past and present neurobiological work, and the theoretical insights into problems of movement offered by homeokinetic physics. Among these are, we think, the beginnings of a principled solution to the degrees of freedom problem, and the tentative claim that coordination and control are emergent consequences of dynamical interaction among non-linear, limit cycle oscillatory processes.     

ASSESSING STIMULUS CONTROL IN NATURAL SETTINGS: AN ANALYSIS OF STIMULI THAT ACQUIRE CONTROL DURING TRAINING

When a learner is taught a new response, the stimuli that influence its display are often unknown. The presence or absence of these stimuli alters the probability of occurrence of the response. By identifying the stimuli influencing the probability of newly acquired responses, interventionists may program for their generalization more effectively and efficiently. This investigation describes the application of an operant methodology to assess functional relationships between responses and specific stimulus variables. Four young adults with moderate mental retardation were taught to include “please” as part of requests they made in school. Four environmental stimuli, present during training, were assessed for the controlling properties they acquired. Each of the four was assessed prior to and after training by presenting it in isolation (i.e., the other three were varied). If the presence of a single stimulus associated with training did not occasion “please,” then pairs of stimuli were probed. The results revealed that single-stimulus probing occasioned responding by only 1 learner; paired-stimulus probing set the occasion for including “please” by 2 others. Control of the 4th learner's responding was lost before training was introduced, because he began including “please” in his requests during baseline. The implications of these results are discussed in terms of analyzing stimulus control and promoting stimulus generalization.     

Discovery of the pendulum and spring dynamics in the early stages of walking

The authors investigated the self-selected, overground walking patterns of 7 children (aged 11 months to 1 year, 5 months) at the initiation of walking (brand-new walkers [BNWs]) and for the next 6 months at 1-month intervals. Walking speed, stride length, and stride frequency increased significantly between the first 2 visits without significant changes in height and weight. The authors calculated sagittal plane angular accelerations of the center of mass over the foot for each step as an indicator of the escapement pulse. Results for the acceleration profiles changed after the 1st visit to positive, single-peaked accelerations that occurred < 0.20 s after initial foot contact. Increases in sagittal plane hip angular displacement and decreases in frontal plane pelvic angular displacement were observed. The pattern changes suggest that children quickly discover appropriately timed and directed escapements that initiate and support the conservative sagittal plane pendulum and spring dynamics observed in older children.     

Putting phonetic context effects into context: a commentary on Fowler (2006)

On the basis of a review of the literature and three new experiments, Fowler (2006) concludes that a contrast account for phonetic context effects is not tenable and is inferior to a gestural account. We believe that this conclusion is premature and that it is based on a restricted set of assumptions about a general perceptual account. Here, we briefly address the criticisms of Fowler (2006), with the intent of clarifying what a general auditory and learning approach to speech perception entails.     

Differential effects of amount on temporal and probability discounting of gains and losses

In four experiments, we compared the effects of delay, probability, and monetary amount on the subjective value of gains and losses. For delayed gains, smaller amounts were discounted more steeply than larger amounts, whereas the opposite pattern was observed with probabilistic gains. For both delayed and probabilistic losses, however, amount had much smaller and less reliable effects on discounting. Taken together, the pattern of differential magnitude effects leads to delayed gains' being discounted significantly more steeply than delayed losses, but only at smaller amounts, whereas probabilistic gains are discounted significantly more steeply than probabilistic losses, but only at larger amounts. Even though the same hyperbola-like function described both individual and group discounting of delayed and probabilistic gains and losses, the present findings suggest that different processes are involved in discounting positive and negative outcomes. Raw data may be downloaded from www.psychonomic.org/archive.     

How Do People Process Health Information? Applications in an Age of Individualized Communication

Advances in computer technology have made it possible to customize communication, including health-education materials, to the specific needs and interests of any individual. Studies show that individually tailored health-education materials are more effective than generic materials in promoting changes in a variety of health-related behaviors. Theory and research in information processing provide an explanation for why such materials are effective. This article discusses current research on how individuals process tailored health information, and discusses directions for future research in this area.