Polydipsia's contribution to temporal discrimination of rats on a fixed interval schedule

This experiment concerned the contribution of polydipsia on the temporal discrimination of rats during a fixed-interval 60-sec. schedule. In this study, the timing accuracy of 12 rats which had access to water during training was compared to that of 12 rats which had no water during training. The rats were trained for 25 sessions on an FI 60-sec. schedule. In early sessions before polydipsia was fully developed, no differences existed between the timing accuracy of the water group and no-water group. As the amount of water drunk by the water group increased as the number of sessions increased, a parallel increase was noted in the timing accuracy of the water group. In the final sessions, a significant difference was found between the timing accuracy of rats in the water group and that of those in the no-water group. It was concluded that polydipsia facilitated the development of the temporal discrimination which is characteristic of a fixed-interval 60-sec. schedule.     

Motoric change subsequent to therapeutic intervention in infants and young children who have cerebral palsy: annotated listing of group studies

This annotated listing is of group reports pertaining to therapeutic strategies utilized with infants and young children who have cerebral palsy. The studies are organized by type of design used.     

Acoustically evoked brain stem potential in Wilson disease

By 48 patients with Wilson's disease the brainstem acoustic evoked potentials were stated. There were 35 pathological findings (73%), 13 were normal (27%). The waves, determined by the middle and upper brainstem (Pons and Mesencephalon) showed most of all pathological changes. Those patients with forms of Wilson's disease called Pseudoskelerose and Pseudoparkinson showed the most pathological findings. But one could watch these findings by about 30% of patients in preclinical stage. This method can possibly be used for early detection of disorders of brainstem functions and in the same way it can be used for control of treatment by patients in preclinical stage.     

A general structural equation model with dichotomous,ordered categorical,and continuous latent variable indicators

A structural equation model is proposed with a generalized measurement part, allowing for dichotomous and ordered categorical variables (indicators) in addition to continuous ones. A computationally feasible three-stage estimator is proposed for any combination of observed variable types. This approach provides large-sample chi-square tests of fit and standard errors of estimates for situations not previously covered. Two multiple-indicator modeling examples are given. One is a simultaneous analysis of two groups with a structural equation model underlying skewed Likert variables. The second is a longitudinal model with a structural model for multivariate probit regressions.This research was supported by Grant No. 81-IJ-CX-0015 from the National Institute of Justice, by Grant No. DA 01070 from the U.S. Public Health Service, and by Grant No. SES-8312583 from the National Science Foundation. I thank Julie Honig for drawing the figures. Requests for reprints should be sent to Bengt Muthén, Graduate School of Education, University of California, Los Angeles, California 90024.     

On tests for correlated proportions in the presence of incomplete data

This paper proposes test statistics based on the likelihood ratio principle for testing equality of proportions in correlated data with additional incomplete samples. Powers of these tests are compared through Monte Carlo simulation with those of tests proposed recently by Ekbohm (based on an unbiased estimator) and Campbell (based on a Pearson-Chi-squared type statistic). Even though tests based on the maximum likelihood principle are theoretically expected to be superior to others, at least asymptotically, results from our simulations show that the gain in power could only be slight.