Least-squares approximation of an improper correlation matrix by a proper one

An algorithm is presented for the best least-squares fitting correlation matrix approximating a given missing value or improper correlation matrix. The proposed algorithm is based upon a solution for Mosier's oblique Procrustes rotation problem offered by ten Berge and Nevels. A necessary and sufficient condition is given for a solution to yield the unique global minimum of the least-squares function. Empirical verification of the condition indicates that the occurrence of non-optimal solutions with the proposed algorithm is very unlikely. A possible drawback of the optimal solution is that it is a singular matrix of necessity. In cases where singularity is undesirable, one may impose the additional nonsingularity constraint that the smallest eigenvalue of the solution be , where is an arbitrary small positive constant. Finally, it may be desirable to weight the squared errors of estimation differentially. A generalized solution is derived which satisfies the additional nonsingularity constraint and also allows for weighting. The generalized solution can readily be obtained from the standard unweighted singular solution by transforming the observed improper correlation matrix in a suitable way.     

A componential model for mental addition

A componential model capable of representing simple and complex forms of mental addition was proposed and then tested by using chronometric techniques. A sample of 23 undergraduate students responded to 800 addition problems in a true-false reaction time paradigm. The 800 problems comprised 200 problems of each of four types: two single-digit addends, one single- and one double-digit addend, two double-digit addends, and three single-digit addends. The results revealed that the columnwise product of addends, a structural variable consistent with a memory network retrieval process, was the best predictor of mental addition for each of the four types of problem. Importantly, the componential model allowed estimation of effects of several other structural variables, e.g., carrying to the next column and speed of encoding of digits. High levels of explained variance verified the power of the model to represent the reaction time data, and the stability of estimates across types of problem implied consistent component use by subjects. Implications for research on mental addition are discussed.     

Twenty-four-hour sleep-wake patterns in a nursing home population

Sleep-activity patterns were objectively recorded over a 24-hr period in 19 elderly nursing home residents. On average, both sleep and wake times were observed during every hour of the 24 recorded hours; however, the sleep pattern of the residents was fragmented so that they rarely experienced even a single hour of consolidated time spent sleeping. It is hypothesized that several independent factors, including compensation for lost sleep, increased total time in bed, weakening of social constraints, and deterioration of the circadian sleep-wake rhythm, are interacting to produce this increase in sleep fragmentation.     

Comparative analysis of actual and mental movement times in two graphic tasks

This study compared the temporal organization of graphic movements executed either actually or mentally. Six subjects had to perform two tasks, writing a sentence and drawing a cube, either as a real performance or as an imagined one, with either the right or the left hand, and with either a small or a large tracing amplitude. In the same subject, for the same hand, mental and actual movement times were both very stable and very close from trial to trial regardless of the tracing amplitude. Thus, mental movements mimic closely real movements in their temporal organization and are likely to involve the same planning program.     

How and when to correct for juror hindsight bias in mental health malpractice litigation: Some preliminary observations

This article examines the hindsight bias in the context of mental health malpractice litigation, analyzes various legal mechanisms for dealing with the bias, and discusses whether the law should strive for debiasing in all mental health malpractice cases.     

Sex role orientations,attributions for achievement,and personal goals of Chinese youth

The role of women in the People's Republic of China has changed dramatically in the last 40 years. This study assesses what impact these changes have had on the attitudes of Chinese youth. The sample consisted of 164 subjects (77 men and 87 women) who completed the Bem Sex Role Inventory, the Objective Fear of Success Measure, a locus of control scale, and a personal goals questionnaire. They also evaluated a painting attributed to artists of different gender and status. The results indicate that the sex role orientations of Chinese students were similar to those of American students. On the Bem inventory, the direction of the sex differences on the sex role scales was the same for U.S. and Chinese students, but the latter had a sex role orientation that, in our culture, is regarded as more “traditional.” Chinese women were significantly more likely to endorse statements expressing fear of success than were Chinese men. On the locus of control measures, Chinese women were more likely than men to attribute their achievement successes to luck and failures to a lack of ability. The women students also attributed affiliation outcomes more to luck than did the men. The most important personal goal cited by both men and women was that of career success. Chinese men placed greater importance than women on achieving wealth, and their expectancy of actually becoming wealthy was higher. Finally, in an evaluation of a painting, Chinese men, but not the women, devalued a painting when it was supposedly the work of a female student artist.     

Computers and commitment to a public management decision: An experiment

Based on results of an experiment, hypotheses are tested concerning the effects of computer use on decision commitment. The experiment required subjects to make an adoption decision regarding a hypothetical government agency's innovation. Subjects could choose from a variety of information sets, some computer based, some not, before making the decision. After their decision the subjects were given “new evidence” that contradicted their initial position. Two experimental treatments included more difficult access to the computer-based information and higher cost for the computer-based information. Results indicate that access difficulty diminishes confidence in decisions and leads to lesser commitment. However, the cost of the computer information seems to have little bearing on decision commitment. Barry Bozeman is director of the Technology and Information Policy Program of the Maxwell School of Public Affairs, Syracuse University, Syracuse NY 13244-4010. There he is professor of public policy and administration and affiliate professor of engineering. His research has focused on organization theory and public management, science and technology policy, and the use of technical information in decision-making. R.F. Shangraw, Jr. is vice president of Independent Project Analysis, Inc., Great Falls, Virginia. Previously, he was assistant professor of public administration at Syracuse University. His research interests include information management, decision-making, and public policy applications of expert systems.     

Frequency analysis of electromyographically measured covert speech behavior

Eleven subjects were asked to silently read slides of the letters “P” and “T,” and to view meaningless control slides similarly as they were presented visually. One-eighth-second electromyographic excerpts were sampled from the baseline and response periods. The data were then transformed into the frequency domain for inferential analyses. The mean power spectral frequencies for the response period were significantly lower than those for the base-line in the overall analysis. There were, however, no significant changes from baseline as a function of kind of stimulus (T, P, or Control) or muscle activated (lips or tongue). It was concluded that there was a generalized responding, not unique to the processing of the specific stimuli studied. Frequency analysis of EMG measures of covert behavior holds some promise of yielding unique information not available through traditional analysis procedures, but more sensitive methods than those used here would be required to demonstrate this.