On models with variable universe

In this paper some parts of the model theory for logics based on generalised Kripke semantics are developed. Löwenheim-Skolem theorems and some applications of ultraproduct constructions for generalised Kripke models with variable universe are investigated using similar theorems of the model theory for classical logic. The results are generalizations of the theorems of [4].     

Recidivism and dependency in a psychiatric population: An investigation with kelly's dependency grid

Over the years there have been varied attempts to explain or predict recidivism, which is a phenomenon whereby psychiatric patients are hospitalized repeatedly. Recent efforts to predict relapse have used specific symptoms (Harris, Bergman, & Bachrach, 1986), diagnoses (Kastrup, 1987; Lally, 1989), postdischarge treatment compliance (Caton, Koh, Fleiss, Barrow, & Goldstein, 1985), and the level of emotional expression in the family environment (Doane, Goldstein, Miklowitz, & Falloon, 1986) as relapse predictors. Despite progress, many unanswered questions remain. The present study examined recidivism from the perspective of personal construct psychology (Kelly, 1955). The Dependency Grid was administered to 33 first-admission patients, 39 recidivists, and 26 controls. As hypothesized, recidivists identified the smallest social network and the fewest people on whom they believed they actually could rely in a crisis. In contrast, patients experiencing their first admission offered an extensive array of individuals to whom they felt they could turn in a crisis. Controls reported the greatest number of social resources potentially available to them, but then selectively chose a sample of them as individuals on whom they would be comfortable relying. Results are discussed in terms of support for Kelly's personal construct theory.     

Generalized latent variable models with non‐linear effects

Until recently, item response models such as the factor analysis model for metric responses, the two‐parameter logistic model for binary responses and the multinomial model for nominal responses considered only the main effects of latent variables without allowing for interaction or polynomial latent variable effects. However, non‐linear relationships among the latent variables might be necessary in real applications. Methods for fitting models with non‐linear latent terms have been developed mainly under the structural equation modelling approach. In this paper, we consider a latent variable model framework for mixed responses (metric and categorical) that allows inclusion of both non‐linear latent and covariate effects. The model parameters are estimated using full maximum likelihood based on a hybrid integration–maximization algorithm. Finally, a method for obtaining factor scores based on multiple imputation is proposed here for the non‐linear model.     

Fixed and optional stopping models for two-choice discrimination times

Several current models for choice- or discrimination-time experiments represent the stimulus as a sequence of independent and identically distributed observations. This paper develops and compares models based on two different stopping rules that a subject might use to terminate his sampling process and convert his perceptual evidence into an observable response. The fixed and optional stopping rules yield different predicted forms for the speed/accuracy tradeoff function and for the relation between mean and variance of response times. These predictions are developed in the general case and then specialized for certain conditions of symmetry, so that the expressions are easier to apply and to compare between models. A later section considers how changes in stopping criteria (either between or within experimental trials) affect predictions about mean response times for correct responses and errors, and then uses these ideas to relate the optional stopping rule for the Random Walk models to those of the Accumulator models. A final section considers specialized models for stimulus detection and intensity discrimination that assume Poisson-distributed sensory input, and relates these models to the present fixed stopping model.     

Multidimensional scaling models for reaction times and same-different judgments

A method for joint analysis of reaction times and same-different judgments is discussed. A set of stimuli is assumed to have some parametric representation which uniquely defines dissimilarities between the stimuli. Those dissimilarities are then related to the observed reaction times and same-different judgments through a model of psychological processes. Three representation models of dissimilarities are considered, the Minkowski power distance model, the linear model, and Tversky's feature matching model. Maximum likelihood estimation procedures are developed and implemented in the form of a FORTRAN program. An example is given to illustrate the kind of analyses that can be performed by the proposed method.The work reported in this paper is supported by Grant A6394 to the first author from the Natural Sciences and Engineering Research Council of Canada. Portions of this study have been presented at the Psychometric Society meeting in Chapel Hill, N.C., in May, 1981. We thank Tony Marley, Jim Ramsay and anonymous reviewers for their helpful comments. MAXRT, a computer program which performs the computations described in this paper may be obtained by writing to the first author.     

Information-theoretic latent distribution modeling: distinguishing discrete and continuous latent variable models

Distinguishing between discrete and continuous latent variable distributions has become increasingly important in numerous domains of behavioral science. Here, the authors explore an information-theoretic approach to latent distribution modeling, in which the ability of latent distribution models to represent statistical information in observed data is emphasized. The authors conclude that loss of statistical information with a decrease in the number of latent values provides an attractive basis for comparing discrete and continuous latent variable models. Theoretical considerations as well as the results of 2 Monte Carlo simulations indicate that information theory provides a sound basis for modeling latent distributions and distinguishing between discrete and continuous latent variable models in particular.     

Classification response times in probabilistic rule-based category structures: Contrasting exemplar-retrieval and decision-boundary models

Experiments were conducted to contrast the predictions from exemplar models and rule-based decisionboundary models of perceptual classification. Observers classified multidimensional stimuli into categories that could be described in terms of easily verbalized logical rules. The critical manipulation was that some pairs of stimuli received probabilistic feedback, whereas other control pairs received deterministic feedback. Despite the probabilistic feedback, the probabilistic pairs and the deterministic pairs were the same distance from idealobserver, rule-based decision boundaries. Across two experiments with varying category structures, observers classified the probabilistic pairs with slower response times (RTs) and lower accuracies than the comparison deterministic pairs. The effects were relatively long term, extending into test blocks in which all feedback was withheld. The results were as predicted by exemplar models, but challenged models that posit that RT is a function solely of the distance of a stimulus from rule-based boundaries. The studies add considerable generality to previous ones and suggest that, even in domains involving rule-based category structures, exemplar-retrieval processes play a significant role. Supplemental materials related to this article may be downloaded from http:// mc.psychonomic-journals.org/content/supplemental.     

Approaches to chemical dependency: chemical dependency and interactive group therapy--a synthesis

Though the focus on interpersonal interaction is a powerful therapeutic factor in group therapy, traditional chemical dependency therapy groups generally fail to employ the interactional group orientation. An interactional approach can be effectively applied to alcoholics if the following guidelines are observed: (1) recovery is always accorded priority, (2) the patient accepts identification as an alcoholic, (3) anxiety is carefully modulated, (4) the proper distinction is made between what the alcoholic is and is not responsible for, (5) the therapist is thoroughly familiar with Alcoholics Anonymous language, steps, and traditions. It is important that therapists not permit misperceptions of A.A. to be used as therapy resistance and that they be able to harness the wisdom of A.A. for psychotherapeutic ends. Group therapists must also be prepared to deal with common themes arising in the treatment of the alcoholic patient: idealization, devaluation, externalization, defiance, grandiosity, conning, and avoidance.     

The integration of continuous and discrete latent variable models: potential problems and promising opportunities

Structural equation mixture modeling (SEMM) integrates continuous and discrete latent variable models. Drawing on prior research on the relationships between continuous and discrete latent variable models, the authors identify 3 conditions that may lead to the estimation of spurious latent classes in SEMM: misspecification of the structural model, nonnormal continuous measures, and nonlinear relationships among observed and/or latent variables. When the objective of a SEMM analysis is the identification of latent classes, these conditions should be considered as alternative hypotheses and results should be interpreted cautiously. However, armed with greater knowledge about the estimation of SEMMs in practice, researchers can exploit the flexibility of the model to gain a fuller understanding of the phenomenon under study.     

Fast and accurate calculations for first-passage times in Wiener diffusion models

We propose a new method for quickly calculating the probability density function for first-passage times in simple Wiener diffusion models, extending an earlier method used by [Van Zandt, T., Colonius, H., & Proctor, R. W. (2000). A comparison of two response-time models applied to perceptual matching. Psychonomic Bulletin & Review, 7, 208-256]. The method relies on the observation that there are two distinct infinite series expansions of this probability density, one of which converges quickly for small time values, while the other converges quickly at large time values. By deriving error bounds associated with finite truncation of either expansion, we are able to determine analytically which of the two versions should be applied in any particular context. The bounds indicate that, even for extremely stringent error tolerances, no more than 8 terms are required to calculate the probability density. By making the calculation of this distribution tractable, the goal is to allow more complex extensions of Wiener diffusion models to be developed.     

Latent variable models for the measurement of flashbulb memories: a comparative approach

Flashbulb memories are defined as vivid, long‐lasting, and detailed memories for the circumstances in which people learned of shocking and important public events, that is the so‐called reception context (Brown & Kulik, 1977). They are considered as highly integrated cores of autobiographical knowledge which aggregate attributes of the reception context (Conway, 1995). The present paper deals with the measurement of flashbulb memories. Data from both a correlational and an experimental study were submitted to confirmatory factor analysis, latent trait model, and latent class model (LCM) procedures. Results confirmed that the clustered nature of flashbulb memories is better assessed by a LCM. The attribute of mass media as a source of the original news seemed to be crucial in defining flashbulb memories. The impact of the mass media was discussed, in that flashbulb memories appear to be not indelible and immune to forgetting. Copyright © 2004 John Wiley & Sons, Ltd.     

Mathematical analysis of the durations of reinforced inter-response times during variable interval reinforcement

In a free-responding situation in which reinforcements are scheduled by a variable interval program, the durations of reinforced inter-response times are shown to be a function of the durations of all inter-response times produced by S and of the frequency of reinforcement.Based on a portion of the author's doctoral dissertation, and supported in part by an NIMH predoctoral research fellowship. Suggestions by W. K. Estes increased the intelligibility of this paper.     

Retention enhancement with post-training picrotoxin: lack of state dependency

Immediate post-training intraperitoneal administration of the GABA-antagonist picrotoxin (0.5 or 1.0 mg/kg) significantly enhanced retention of CD1 mice tested 24 h after training in an inhibitory avoidance task. Administration of picrotoxin prior to the retention test did not affect the retention performance of mice given post-training injections of either saline or picrotoxin. These findings indicate that the memory-enhancing effects of post-training administration of picrotoxin are not state-dependent.     

Obsessional-compulsive checking: Experimental replication and development

The purpose of this experiment was to resolve some inconclusive findings from an earlier study on the effects of compulsive checking rituals. Twelve obsessional-compulsive checkers carried out a provoking act followed by their compulsive checking ritual, in natural situations, under two conditions—E present and E absent. The provoking act produced subjective discomfort, tension, worry and anxiety; these feelings were reduced after completion of the checking ritual. Both the increases and post-ritual decreases in discomfort were more pronounced in the spontaneous occurrence condition (E absent). The results are consistent with the hypothesis that compulsive rituals serve to reduce discomfort.     

Semi‐parametric proportional hazards models with crossed random effects for psychometric response times

The semi‐parametric proportional hazards model with crossed random effects has two important characteristics: it avoids explicit specification of the response time distribution by using semi‐parametric models, and it captures heterogeneity that is due to subjects and items. The proposed model has a proportionality parameter for the speed of each test taker, for the time intensity of each item, and for subject or item characteristics of interest. It is shown how all these parameters can be estimated by Markov chain Monte Carlo methods (Gibbs sampling). The performance of the estimation procedure is assessed with simulations and the model is further illustrated with the analysis of response times from a visual recognition task.     

Subgrouping with psychiatric inpatients in group psychotherapy: linking dependency and counterdependency

Abstract A model of inpatient group psychotherapy that focuses on two frequently observed patient subgroups reflecting contrasting attitudes toward authority is presented. The counterdependent subgroup overly values autonomy, opposes unit restrictions, and rejects treatment. The dependent subgroup tends to accept the unit's treatment and structure but is overly passive. In this model these attitudes are addressed in order to help patients adapt to the unit and to facilitate discharge. The author describes a three-stage group designed to help patients achieve these goals.