Delay discounting in current and never-before cigarette smokers: similarities and differences across commodity,sign, and magnitude

Research has found that nicotine-dependent individuals delay discount monetary gains at a higher rate than matched controls. Delay discount rates, however, have also been found to vary across within-subject variables such as the magnitude of the outcome (e.g., 10 dollars or 1,000 dollars), whether the outcome constitutes a gain or a loss, and the commodity being evaluated (e.g., money or health). The present study comprehensively investigated the differences in delay discounting between current and never-before cigarette smokers and across these within-subject variables. Both groups exhibited a magnitude, sign, and commodity effect. Current smokers' delay discount rates for monetary outcomes, however, were higher than never-before smokers across all magnitudes and both signs. This trend was also found for delayed health outcomes, but failed to reach significance.     

An analysis of response,direction, and place learning in an open field and T maze

Rats were trained to locate food in a response, direction, or place problem on an open field located at 2 positions. In Experiment 1, both the response and direction groups solved the problem. The place group failed to solve the task in approximately 300 trials. Experiment 2 demonstrated that rats need distinguishable start points to solve a place problem when neither a response nor a direction solution is available. Findings from Experiment 3 suggest that a combination of path traveled and distinct cues help to differentiate start points. Experiment 4 replicated the findings using a T maze. These results suggest "place" solutions are difficult for rats. The data are discussed with respect to conditional learning and modern spatial mapping theory.     

An investigation of hierarchical Bayes procedures in item response theory

Hierarchical Bayes procedures for the two-parameter logistic item response model were compared for estimating item and ability parameters. Simulated data sets were analyzed via two joint and two marginal Bayesian estimation procedures. The marginal Bayesian estimation procedures yielded consistently smaller root mean square differences than the joint Bayesian estimation procedures for item and ability estimates. As the sample size and test length increased, the four Bayes procedures yielded essentially the same result.The authors wish to thank the Editor and anonymous reviewers for their insightful comments and suggestions.     

Misinterpretation of instructions in an aftereffect task

Some subjects in studies of kinesthetic aftereffect erroneously believe the task is to show the width of the aftereffect inducing rather than the standard stimulus. Although such subjects may be encountered rarely, the errors they make are very large. Precautionary steps are indicated.     

Individual differences in visual imaging and the voluntary control of heart rate.

The role of visual imagery in the bidirectional control of heart rate (HR) was explored in 24 subjects. While voluntary HR increases were reliably demonstrated with and without HR feedback, appropriate HR decreases were modest and inconsistent. Changes in respiration rate (RR) generally paralleled the alterations in HR. Eighteen of the subjects reported conventionally using visual imagery to effect HR changes. For these subjects, vividness of visual imagery scores and the extent of HR change showed indications of a direct relationship in the HR increase condition. However, in the HR decrease condition, it was concomitant RR changes which were associated with the vividness and the control of imagery production. The remaining six subjects, who reported not employing visual imagery, demonstrated superior HR acceleration to the imaging subjects. Further, while the imaging subjects did not benefit from the introduction of feedback, the six non-imaging subjects showed reliably greater HR acceleration as a result of feedback introduction.     

Evaluating the conformity of sociometric measurements

The problem of comparing two sociometric matrices, as originally discussed by Katz and Powell in the early 1950's, is reconsidered and generalized using a different inference model. In particular, the proposed indices of conformity are justified by a regression argument similar to the one used by Somers in presenting his well-known measures of asymmetric ordinal association. A permutation distribution and an associated significance test are developed for the specific hypothesis of no conformity reinterpreted as a random matching of the rows and (simultaneously) the columns of one sociometric matrix to the rows and columns of a second. The approximate significance tests that are presented and illustrated with a simple numerical example are based on the first two moments of the permutation distribution, or alternatively, on a random sample from the complete distribution.Partial support for the research of the first author was provided by the National Science Foundation through SOC 75-07860. Equal authorship is implied. The work was done when the first author was at the University of Wisconsin.     

The comparison and fitting of given classification schemes

A permutation procedure is described for statistically comparing a given classification scheme, characterized as a hierarchically organized collection of subsets, to either a proximity matrix or a second classification scheme defined on the same basic set of objects. To prevent a bias that may result when an optimization method is used to construct the classification structures being considered, it is assumed that the desired comparisons involve classifications and/or proximities that have been derived from separate sources. In addition to an extensive number of examples used to clarify the major points in the presentation of the inference strategy, several heuristic optimization techniques are also introduced and illustrated. These latter procedures attempt to “fit” the form of a target classification structure by relabeling the rows and simultaneously the columns of a given proximity matrix to maximize the correspondence between the fixed target and the relabeled proximity matrix.     

Cardiac response as an index of the effect of aversion therapy

Recent research shows that aversion conditioning produces conditioned aversions to target stimuli. Conditioned aversions are manifest in the following posttreatment changes in Ss' responses to target stimuli: increased negative evaluations, decreased contact or consumption, and increased phasic heart-rate responses (HRRs). Research on aversion therapy for additive disorders reveals that HRR is a particularly important index of therapeutic change as it is predictive of latency to relapse to drug use. We speculate that aversion conditioning increases Ss' fear and repugnance of target stimuli, that HRRs accurately reflect such defensive responses and that magnitude of defensive response is positively related to latency to relapse. In addition to defensive responding, we believe that HRRs may reflect coping-response or active-avoidance information processing.