Cluttering upgraded

The articles in this special edition have been scrutinized for new information on the problem of cluttering. The etiology of the disorder is still a riddle, but we now seem to know more about its relationship to learning disorders. Cluttering is not only a fluency and language disorder, but pragmatic rules are also violated by clutterers.

The most encouraging advances presented in this special edition are within assessment and therapy. New diagnostic instruments have been developed. The widely accepted view of a poor prognosis for clutterers has been partly refuted, even if we still only have a couple of case studies showing long-time effects of therapy. Recommendations for further research and development are suggested.     

DIAGNOSTIC EXPLOITATION OF VISUAL AFTEREFFECT MEASURES IN A MODERATELY DEPRESSIVE PATIENT GROUP

SMITH, G. J. W., FRIES, I., ANDERSSON, A. L. & RIED, J. Diagnostic exploitation of visual aftereffect measures in a moderately depressive patient group. Scand. J. Psychol. , 1971, 12, 68–79.–A group of 39 moderately depressive patients were tested before and after therapy with two serial aftereffect tests. One of them concerned size, intensity, and color of projected afterimages (AI), the other the duration of spiral aftereffects (SAE). AI and SAE data correlated highly with psychiatric ratings of depressive retardation, anxiety, and compulsion. These correlations formed the nucleus of three independent dimensions in a factorial space.     

The use of extreme groups in assessing relationships

The relationship between variables in applied and experimental research is often investigated by the use of extreme (i.e., upper and lower) groups. Earlier analytical work has demonstrated that the extreme groups procedure is more powerful than the standard correlational approach for some values of the correlation and extreme group size. The present article provides methods for using the covariance information that is usually discarded in the classical extreme groups approach. Essentially, then, the new procedure combines the extreme groups approach and the correlational approach. Consequently, it includes the advantages of each and is shown to be more powerful than either approach used alone.     

DIFFERENCES IN VERBALLY EXPRESSED COGNITION FOLLOWING LEFT AND RIGHT VENTROLATERAL THALAMOTOMY

A lmgren , P.-E., A ndersson , A. L. & K ullberg , G. Differences in verbally expressed cognition following left and right ventrolateral thalamotomy. Scand. J. Psychol ., 1969, 10 , 243–249.—Patients with Parkinson's disease, subjected to ventrolateral thalamotomy, 44 on the left side and 23 on the right, were tested pre- and postoperatively with the Color-Word Test (CWT), a memory test of word pairs (WPT), and Raven's Progressive Matrices Test (PMT). As to performance change from pre- to postoperative testing, there were significant differences between the two groups of operatees on the CWT (p =0.000001, at best) and the WPT(p = 0.01), implying a less effective postoperative performance in the group with left-sided thalamic lesion. Such a lesion seems to impair the continuous suppression of previously relevant information in connection with selection of the appropriate verbal response.     

The classification of individuals into two criterion groups on the basis of a discontinuous payoff function

An analytic method is presented for optimally classifying individuals into two subgroups on the basis of a cutting score on a test or test composite. The development assumes the test and criterion scores to be normally distributed, and the correlation surface to be bivariate normal. It is further assumed that individuals belong to the first or second sub-group depending on whether their criterion score is above or below a specified value. The predictor cutting score is determined so as to maximize the expected value of the decision procedure, taking gains and losses associated with correct and incorrect assignments into account.The opinions expressed are those of the authors and do not necessarily reflect those of the Navy Department. This research was supported in part by a grant from the National Institute of Mental Health, MH 10449-01.     

Finite Mixtures of Hidden Markov Models for Longitudinal Responses Subject to Drop out

Abstract

Drop out is a typical issue in longitudinal studies. When the missingness is non-ignorable, inference based on the observed data only may be biased. This paper is motivated by the Leiden 85+ study, a longitudinal study conducted to analyze the dynamics of cognitive functioning in the elderly. We account for dependence between longitudinal responses from the same subject using time-varying random effects associated with a heterogeneous hidden Markov chain. As several participants in the study drop out prematurely, we introduce a further random effect model to describe the missing data mechanism. The potential dependence between the random effects in the two equations (and, therefore, between the two processes) is introduced through a joint distribution specified via a latent structure approach. The application of the proposal to data from the Leiden 85+ study shows its effectiveness in modeling heterogeneous longitudinal patterns, possibly influenced by the missing data process. Results from a sensitivity analysis show the robustness of the estimates with respect to misspecification of the missing data mechanism. A simulation study provides evidence for the reliability of the inferential conclusions drawn from the analysis of the Leiden 85+ data.