Estimation for structural equation models with missing data

A direct method in handling incomplete data in general covariance structural models is investigated. Asymptotic statistical properties of the generalized least squares method are developed. It is shown that this approach has very close relationships with the maximum likelihood approach. Iterative procedures for obtaining the generalized least squares estimates, the maximum likelihood estimates, as well as their standard error estimates are derived. Computer programs for the confirmatory factor analysis model are implemented. A longitudinal type data set is used as an example to illustrate the results.This research was supported in part by Research Grant DAD1070 from the U.S. Public Health Service. The author is indebted to anonymous reviewers for some very valuable suggestions. Computer funding is provided by the Computer Services Centre, The Chinese University of Hong Kong.     

Visual control of step length during running over irregular terrain

Running over uneven ground requires visually regulating step length to secure proper footing. To examine how this is achieved, we studied subjects running on a treadmill on a series of irregularly spaced targets. The movements of their lower limbs and coccyx relative to the targets were monitored opto-electronically by a Selspot system. The results indicated that step length was adjusted to strike the targets primarily by varying the vertical component of impulse applied to the ground during the stance phase. In contrast, horizontal impulse was not varied significantly, and changing the reach forward of the foot on landing contributed little to variation in step length. Changing the vertical impulse simply altered the step time proportionately. Thus the data are consistent with a time-based model in which vertical impulse is modulated by the optic variable delta tau (Lee, 1976) specifying the time gap that has to be bridged by the runner between two targets.     

Visual and auditory attention performance in hyperactive children: Competence or compliance

The effect of self-control and compliance on the attentional performance of hyperactive children was assessed. Visual and auditory attention tasks were presented in conditions in which the experimenter was either absent and therefore not imposing external control, or present and therefore imposing some degree of control. There was no difference in performance between hyperactives and controls when the experimenter was present, but the hyperactives' performance showed a greater deterioration than controls when the experimenter was absent. The amount of movement displayed during the tasks was greater for hyperactives and increased more for this group during experimenter-absent conditions. The results support the contention that noncompliance is a major contributor to the poor performance of hyperactive children, which can be seen as an application deficit rather than an ability deficit. These findings have relevance for the current debate on the association between hyperactivity and conduct disorder, and from an applied perspective they serve to stress the importance of situational contributors to the problem behaviors of hyperactive children.     

Attitudes to new technology in relation to social beliefs and group memberships: A preliminary investigation

Though the term “new technology” is widely used and discussed, there has been very little systematic study of attitudes to technology and their relation to other beliefs and group memberships. This article describes an initial investigation into the nature of attitudes towards new technology (n=534 undergraduates) and demonstrates that, as yet, these attitudes are only weakly structured and are not fully integrated with other social beliefs. General evaluations of the benefits of technological advance appear to be almost unrelated to beliefs about the inevitability of these advances or the desire to acquire training to deal with them. Contrary to popular expectations, evaluations of video games are unrelated to other beliefs about technology while other social beliefs are, as yet, only weakly integrated with these attitudes. This study also identifies gender differences in the assessment of potential benefits and highlights other differences attributable to academic group memberships. These finding are discussed with reference to the literature on sex-role stereotyping and group socialization processes.     

Criminal profiling from crime scene analysis

Since the 1970s, investigative profilers at the FBI's Behavioral Science Unit (now part of the National Center for the Analysis of Violent Crime) have been assisting local, state, and federal agencies in narrowing investigations by providing criminal personality profiles. An attempt is now being made to describe this criminal-profile-generating process. A series of five overlapping stages lead to the sixth stage, or the goal of apprehension of the offender: (1) profiling inputs, (2) decision-process models, (3) crime assessment, (4) the criminal profile, (5) investigation, and (6) apprehension. Two key feedback filters in the process are: (a) achieving congruence with the evidence, with decision models, and with investigation recommendations, and (b) the addition of new evidence.     

Norms for employed daughters' and sons' behavior toward frail older parents

This study examined whether norms that concerning assisting frail older parents were different for daughters than for sons when the adult children are members of dual-earner couples. Data were gathered by telephone interviews from a probability sample of 315 adults residing in western Alabama. Of the 18 statements presented, statistically significant differences between the expectations for daughters and sons occurred in only three cases (help with housework, meal preparation, and yard work), suggesting substantial support for norms of equalitarianism. Further, there were few differences between the expectations held by females and by males for daughters and sons. Generally, the results suggested strong support for behaviors that facilitate the independent living of both adult children and their frail older parents.The authors acknowledge with thanks the assistance of the University of Alabama's Capstone Poll, which collected the data for this study.     

Survey on present and potential instructional use of computers in psychology

A survey of academic psychologists was taken to determine present use of computers in instruction, willingness to use good education software, and kinds of potential uses of computers in psychology courses. A majority of the respondents reported using computers in instruction. Respondents indicated substantial willingness to adopt computer-based courseware. Respondents believed that a variety of uses, including classroom demonstrations and student experiments, would facilitate student learning. The results of the survey are compared with the instructional modules the task force is developing.     

The processing of the sounds and meanings of ongoing speech by aphasic subjects

The ability of aphasic subjects to process the sounds and meanings of ongoing speech was tested. Subjects, 10 aphasic and 20 control, heard test sentences which contained one member of phonemically similar word pairs in one of three semantic contexts: congruent, neutral, and noncongruent. Immediately after hearing a sentence, subjects were to indicate which member of the word pair had been in the sentence. All subject groups had similar overall patterns of response to the different semantic contexts. The division of aphasic subjects into groups of high and low comprehenders revealed response differences. High comprehending aphasic subjects, like control subjects, demonstrated interactive processing of the sounds and meaning of speech while low comprehending aphasic subjects did not.     

REDUCING SELF-INJURY AND CORRESPONDING SELF-RESTRAINT THROUGH THE STRATEGIC USE OF PROTECTIVE CLOTHING

We examined the use of protective clothing to reduce a retarded male's face-punching and leg-kicking and two corresponding forms of self-restraint—arm and leg self-restraint. The resident was observed each day in three sessions of randomly ordered conditions (one condition per session): without any protective clothing, with a padded helmet, and with a padded helmet and padded slippers. Use of the padded helmet substantially reduced face-punching and arm self-restraint. The addition of padded slippers reduced leg-kicking and leg self-restraint. These results suggest a practical and effective means of controlling self-injury and self-restraint. They are also consistent with the possibility that the resident's arm restraint was maintained in part by escape or avoidance of face-punching and that his leg restraint was maintained in part by escape or avoidance of leg-kicking.