The development of children's rule use on the balance scale task

Cognitive development can be characterized by a sequence of increasingly complex rules or strategies for solving problems. Our work focuses on the development of children's proportional reasoning, assessed by the balance scale task using Siegler's (1976, 1981) rule assessment methodology. We studied whether children use rules, whether children of different ages use qualitatively different rules, and whether rules are used consistently. Nonverbal balance scale problems were administered to 805 participants between 5 and 19 years of age. Latent class analyses indicate that children use rules, that children of different ages use different rules, and that both consistent and inconsistent use of rules occurs. A model for the development of reasoning about the balance scale task is proposed. The model is a restricted form of the overlapping waves model (Siegler, 1996) and predicts both discontinuous and gradual transitions between rules.     

Speech parts as Poisson processes

This paper presents evidence that six of the seven parts of speech occur in written text as Poisson processes, simple or recurring. The six major parts are nouns, verbs, adjectives, adverbs, prepositions, and conjunctions, with the interjection occurring too infrequently to support a model. The data consist of more than the first 5000 words of works by four major authors coded to label the parts of speech, as well as periods (sentence terminators). Sentence length is measured via the period and found to be normally distributed with no stochastic model identified for its occurrence. The models for all six speech parts but the noun significantly distinguish some pairs of authors and likewise for the joint use of all words types. Any one author is significantly distinguished from any other by at least one word type and sentence length very significantly distinguishes each from all others. The variety of word type use, measured by Shannon entropy, builds to about 90% of its maximum possible value. The rate constants for nouns are close to the fractions of maximum entropy achieved. This finding together with the stochastic models and the relations among them suggest that the noun may be a primitive organizer of written text.     

MCMC estimation and some model-fit analysis of multidimensional IRT models

A Bayesian procedure to estimate the three-parameter normal ogive model and a generalization of the procedure to a model with multidimensional ability parameters are presented. The procedure is a generalization of a procedure by Albert (1992) for estimating the two-parameter normal ogive model. The procedure supports analyzing data from multiple populations and incomplete designs. It is shown that restrictions can be imposed on the factor matrix for testing specific hypotheses about the ability structure. The technique is illustrated using simulated and real data. The authors would like to thank Norman Verhelst for his valuable comments and ACT, CITO group and SweSAT for the use of their data.     

Rotation in the dynamic factor modeling of multivariate stationary time series

A special rotation procedure is proposed for the exploratory dynamic factor model for stationary multivariate time series. The rotation procedure applies separately to each univariate component series of aq-variate latent factor series and transforms such a component, initially represented as white noise, into a univariate moving-average. This is accomplished by minimizing a so-called state-space criterion that penalizes deviations of the rotated solution from a generalized state-space model with only instantaneous factor loadings. Alternative criteria are discussed in the closing section. The results of an empirical application are presented in some detail.This research was supported by the Institute for Developmental and Health Research Methodology, University of Virginia.     

Identifiability of nonlinear logistic test models

The linear logistic test model (LLTM) specifies the item parameters as a weighted sum of basic parameters. The LLTM is a special case of a more general nonlinear logistic test model (NLTM) where the weights are partially unknown. This paper is about the identifiability of the NLTM. Sufficient and necessary conditions for global identifiability are presented for a NLTM where the weights are linear functions, while conditions for local identifiability are shown to require a model with less restrictions. It is also discussed how these conditions are checked using an algorithm due to Bekker, Merckens, and Wansbeek (1994). Several illustrations are given.This article was written while the first author was a post doctoral fellow at the university of Twente. He gratefully acknowledges the university's hospitality and the financial support by NWO (project nr. 30002).     

A computational model of frontal lobe dysfunction: working memory and the Tower of Hanoi task

A symbolic computer model, employing the perceptual strategy, is presented for solving Tower of Hanoi problems. The model is calibrated—in terms of the number of problems solved, time taken, and number of moves made—to the performance of 20 normal subjects. It is then "lesioned" by increasing the decay rate of elements in working memory to model the performance of 20 patients with lesions to the prefrontal cortex. The model captures both the main effects of subject groups (patients and normal controls) performance, and the subject groups (patients and normal controls) by problem difficulty interactions. This leads us to support the working memory hypothesis of frontal lobe functions, but for a narrow range of problems.     

Scharffs' Application of Hopper's Concept: “Incohesion: Aggregation/Massification”

We begin by stating our understanding of the concepts presented in Hopper's paper, then comment on the clinical illustration, and conclude by describing two group situations in which we have applied the concepts we have taken from Hopper's paper. Hopper's fourth basic assumption applies to our work as individual psychoanalysts, family therapists, and group leaders because it integrates psychoanalytic and social understanding. We demonstrate how and why we find Hopper's idea to be a useful advance.     

The Possible Place of Cognitive Appraisal in the ABC Model Underlying Rational Emotive Behavior Therapy

In a critique of Ellis' Rational Emotive Behavior Therapy (REBT) theory of personality, it has been argued that, among other strategies, REBT personality theory could be significantly advanced by attempting to incorporate within it already established theoretical constructs compatible with the cognitive-behavioral movement. Richard Lazarus' prominent, well-articulated, and extensively studied theoretical construct of cognitive appraisal seems ideal in this regard. In the present article, the relevant and salient aspects of Lazarus' construct are described. An attempt is then made to delineate the possible place of cognitive appraisal in the ABC model underlying REBT. Finally, the clinical implications of this proposed ABC model refinement are then explored, and an additional REBT therapeutic strategy based upon the cognitive appraisal construct, reappraisal training, is suggested and briefly described.     

Palm Beach County Child Abuse and Neglect System Redesign: Initial Process Evaluation

For the families in Palm Beach County who entered the child abuse and neglect system as a result of having a child placed into emergency shelter, their experience was that the system was frequently intimidating, confusing, and fragmented. The reaction of the children and their families to this system was often defensiveness and resistance. To increase the system's effectiveness, it was redesigned and privatized. The redesigned system included centralized shelter placement, a comprehensive assessment, independent service coordination, and treatment service provision within a managed care model. By emphasizing family involvement and quality service provision, the goal was to increase voluntary participation and improve family outcomes. Based on initial data, it appears that the redesigned system has been successfully implemented and has made notable progress toward meeting its system flow timeframes. The initial data also indicate that high percentages of families are participating in and are satisfied with the system, that children are spending less time in shelter placements, and that only one family has reentered the system.     

Mentoring: Some ethical considerations

To counter confusion about the term ‘mentor’, and address concerns about the scarcity of mentoring, I argue for an “honorific” definition, according to which a mentor is virtuous like a saint or hero. Given the unbounded commitment of mentors, mentoring relationships must be voluntary. In contrast, the role of advisor can be specified, mandated, and monitored. I argue that departments and research groups have a moral responsibility to devise a system of roles and structures to meet graduate students’ and postdoctoral fellows’ needs for information and advice. An earlier version of this paper was presented at a conference sponsored by the National Science Foundation on Mentoring and Research Values: Students as Vital Human Resources, Chicago, March 1995.