Punishment of temporally spaced responding

The responses of pigeons were maintained by a DRL schedule of food reinforcement. With this schedule, responses were reinforced only when a fixed period of time elapsed without an intervening response. Punishment of all responses reduced the frequency of these responses as a direct function of the punishment intensity. As a consequence of the increased temporal spacing of responses, more reinforcements resulted during punishment. Under progressively higher intensities of punishment, the reinforcement frequency increased to a maximum value and then decreased at the highest intensities. The increased frequency of reinforcement which resulted during punishment did not counteract the suppressive effect of punishment, nor did it lead to a low response rate after punishment was removed. Punishment did not reduce the inter-response time distribution uniformly, but rather especially reduced the number of short inter-response times. Even at the low punishment intensities, the number of short inter-response times was considerably reduced. After punishment was discontinued, performance recovered almost completely after a compensatory burst. The number as well as the temporal pattern of responses returned to normal.     

The surface-weight illusion: on the contribution of grip force to perceived heaviness

Previous psychophysical studies have shown that an object, lifted with a precision grip, is perceived as being heavier when its surface is smooth than when it is rough. Three experiments were conducted to assess whether this surface-weight illusion increases with object weight, as a simple fusion model suggests. Experiment 1 verified that grip force increases more steeply with object weight for smooth objects than for rough ones. In Experiment 2, subjects rated the weight of smooth and rough objects. Smooth objects were judged to be heavier than rough ones; however, this effect did not increase with object weight. Experiment 3 employed a different psychophysical method and replicated this additive effect, which argues strongly against the simple fusion model. The whole pattern of results is consistent with a weighted fusion model in which the sensation of grip force contributes only partially to the perceived heaviness of a lifted object.     

FUNCTIONAL ANALYSIS OF SEPARATE TOPOGRAPHIES OF ABERRANT BEHAVIOR

We conducted a functional analysis of distinct topographies of aberrant behavior displayed by 4 clients. We first analyzed the behaviors in an aggregate fashion and then separated the behaviors to formulate hypotheses about the maintaining variables for each behavior. The procedures were used in a two-phase experiment. During Phase 1, two extended functional analyses were completed, one in an inpatient unit and one in a special education classroom. During Phase 2, two brief functional analyses were completed in an outpatient clinic. Results indicated that hypotheses of separate functions for distinct behaviors can be generated using both extended and brief functional analyses when the results are graphed in the aggregate and are separated by response topography. The results also suggest that these methods can improve the accuracy of data interpretation and treatment selection.     

Adaptive Dynamics of the Leg Movement Patterns of Human Infants: II. Treadmill stepping in Infants and Adults

Infant treadmill steps have many temporal and kinematic similarities to adult walking. Kinematic similarities can result from different patterns of underlying torque, however. In this study, we used inverse dynamics to compare the patterns and contributions of active (muscle) and passive (gravity and motion-dependent) torques in the swing phase of treadmill stepping in 7-month-old infants and adults. Results indicated that adults consistently used muscle torque to initiate and terminate swing, but that passive torques accounted for leg motion during most of the swing phase. Infants, in contrast, displayed multiple patterns of torque contributions during swing. In the most frequently occurring infant pattern, muscle torque remained flexor throughout swing and joint reversals were due to the dominant passive gravitational torque. The kinetic data suggest that the temporally and kinematically similar treadmill steps produced by adults and infants do not emanate from a unique set of neural commands to the muscles, but from a flexible interplay between multiple internal as well as external elements. These data suggest that the intrinsic dynamics of the human system provide a medium out of which, given a supportive context, stable patterns can emerge spontaneously. During development, voluntary controlled movement patterns must build on these intrinsic dynamics.     

Is it possible to prepare the second component of a movement before the first one?

Experiment 1 utilized a choice reaction time paradigm to examine whether advance information about the second component of a movement has similar effects upon movement initiation and execution as advance information about the first component. Four stimuli were assigned to four goal keys. Subjects responded with the index finger of their preferred hand. They had to press on of two intermediate keys before pressing the assigned stimulus goal key. Advance information signaled one pair of goal keys in such a way that either the first or the second movement component was unequivocally specified before the response signal appeared. Shorter reaction times resulted when the first component was precued. Further control conditions showed that advance information about the second movement component could not be utilized for movement preparation. Experiment 2 ruled out a perceptual interpretation of this effect. Experiment 3 showed that preparation time for two-component movements are longer than for one-component movements. The study permits the conclusions that speeded two-component movements are controlled by motor programs and that advance information about the first movement component is required before the second movement component can be programmed.     

Computers and the nature of farm management

The introduction of computer-based information systems to be used by farmers, as in many other fields, is preceded mostly by great expectations. Some persons even tend to think that eventually the computer might take over farm management. This article tries to make an assessment of the validity of such expectations. Based upon a study among Swedish farmers, it examines the nature of farmers' decision-making. The latter is based upon an adaptive rationality, as opposed to the normative models of formal rationality used by scientists. Essential to this rationality are coordination skills: the ability of farmers to arrange the many interacting factors important to the totality of a farm in a satisfactory way. What the farmer needs in this complex situation is personal communication and tacit knowledge, knowledge that cannot be reduced to facts and rules. Consequently computer-based information systems can be useful tools only in some aspects of farm management, but they will never replace farmer's decision-making. To understand the possibilities of the computer as a tool in farm management, a distinction between interpretation skills and application skills is necessary.     

A computer program for Spearman-K?rber and probit analysis of psychometric function data.

PMETRIC is a computer program for the analysis of observed psychometric functions. It can estimate the parameters of these functions, using either probit analysis (a parametric technique) or the Spearman-K?rber method (a nonparametric one). For probit analysis, either a maximum likelihood or a minimum chi 2 criterion may be used for parameter estimation. In addition, standard errors of parameter estimates can be estimated via bootstrapping. The program can be used to analyze data obtained from either yes-no or m-alternative forced-choice tasks. To facilitate the use of PMETRIC in simulation work, an associated program, PMETGEN, is provided for the generation of simulated psychometric function data. Use of PMETRIC is illustrated with data from a duration discrimination task.     

Organizational citizenship behavior and organizational commitment in Nepal

The present study examines the structure of organizational citizenship behavior (OCB) and its relation to organizational commitment in Nepal. Four-hundred and fifty employees of five Nepalese organizations filled out standardized questionnaires. Exploratory and confirmatory factor analyses revealed two factors of OCB, altruism and compliance, replicating Western models of extra-role behavior. Structural equation analysis showed a positive relation between affective and normative commitment on the one hand and both citizenship factors on the other. Continuance commitment was negatively related to compliance and unrelated to altruism. The findings thus confirmed the structure and usefulness of the concepts in an under-researched geographical area. Findings of the research are discussed within the Nepalese sociocultural context.