Maximum-likelihood estimation of the accuracy of auditory discrimination in the absence of an overt response to every stimulus

In research on human performance in which techniques for estimating hits and false-alarm rates are used in conjunction with other measurements, such as evoked potentials, it is necessary to devise special data-collection methods. This paper describes such data-collection methods, together with a statistical method for summarizing the data. The statistical method consists of setting up a probability model whose parameters describe the process and then estimating the parameters using maximum likelihood.     

The Effects of Using the International Versus Comprehensive System Rorschach Norms For Children,Adolescents, and Adults

Currently, there is some debate about whether to use Comprehensive System norms (CS; Exner, 2003 Exner, J. E. (2003). The Rorschach: A Comprehensive System: Vol. 1. Basic foundations (4th ed.). New York, NY: Wiley. [Google Scholar]) or the Composite International Reference Values (CIRV; Meyer, Erdberg, &; Shaffer, 2007 Meyer, G. J., Erdberg, P., &; Shaffer, T. W. (2007). Toward international normative reference data for the Comprehensive System. Journal of Personality Assessment, 89(Suppl. 1), S201–S216.[Taylor &; Francis Online], [Web of Science ®] , [Google Scholar]) when interpreting Rorschach Inkblot Method (RIM; Rorschach, 1921 Rorschach, H. (1921). Psychodiagnostik [Psychodiagnostics]. Bern, Switzerland: Bircher. [Google Scholar]) protocols administered with the CS method. The goal of this study is to assist clinicians in making this decision by providing information about the effects of choosing one option or the other. Accordingly, this research evaluates the effects of using the CS versus CIRV norms with children, adolescents, and adults. First, we identified 43 variables for which the CS and the CIRV for children and adolescents differ from each other by at least a Cohen's d value of .50. Next, we evaluated whether these divergent variables are the same as those previously identified as divergent for the adult population. Results showed that for both children and adolescents, as well as for adults, relying on CS norms versus CIRV would result in interpretations that are more pathological in terms of (a) perception and thinking, (b) psychological resources and cognitive and emotional abilities, and (c) representations of human relationships. A discussion on the clinical effects of using one versus the other set of norms follows.     

Changing industry to continuous operations: Different strokes for different plants

A survey method was designed to evaluate the effect of shift work on industrial workers and to develop recommendations for 7-day around-the-clock production work systems. A Work-Sleep Survey was then offered to 2,340 hourly and salaried workers at four plants. Each plant was in the rubber and plastic products industry and on 5-day around-the-clock operations using permanent shifts. Of the total workers, 90.38% responded to the survey. The results agree with the findings of a previous survey, offered to workers through their unions, using many of the same survey items. The plants were found to differ in worker demographics, habits, and preferences. This survey method is helpful as an aid for the design and evaluation of shift-work systems tailored to specific worker and plant requirements.     

Individual Restraint and Group Efficiency in Commons Dilemmas: The Effects of Two Types of Environmental Uncertainty1

In most real-world commons, the exact resource quantity is rarely known, and the rate at which the resource regenerates is not always predictable. Annual salmon runs, for example, are based on breeding rates and many other factors; those fishing never know exactly how many fish will be available for next year's season. The present study employed a computerized commons dilemma simulation to investigate the impact of uncertainty in pool size and regeneration rate on individuals harvest choice and the efficiency with which groups managed the resource pool. Both types of uncertainty produced significant declines in individual restraint and group efficiency, although the group-level effects tended to be stronger than those at the individual level. Implications for the management of real-world commons are discussed.     

Methodological considerations in the study of delay discounting in intertemporal choice: A comparison of tasks and modes

An experimental comparison of two commonly used delay-discounting procedures (binary choice and fill in the blank) and modes of administration (paper and pencil and computer based) was conducted. Statistically significant main effects were found for task type—steeper discounting was observed in the binary-choice task— but not for mode of administration. As simple evidence of validity, hyperbolic curves consistently provided a better fit to the data than did exponential curves for both tasks. Further, magnitude effects were also observed across conditions. Correlational results varied largely as a function of the discounting index (either k or area under the curve) under consideration. Across the two tasks, discounting indices showed modest levels of reliability [r(AUC)=.33; r(k)=.75]. The findings pointed to refinements for both the methodology and criteria that are used to study delay discounting and raised questions about the commonly assumed relationship between discounting and the construct of impulsivity.     

Discrimination is more closely associated with perceived similarity than with distance and color

Diverse factors affect perceived similarity and discrimination, with high perceived similarity associated with poor discrimination. To investigate this hypothesis, college students made speeded same-different discriminations between 2 achromatic colors when they were contiguous and separated, did the same with 2 chromatic colors, and rated similarity. Compared with chromatic color, the separation for achromatic color impaired the performance on different stimuli more than on same stimuli with response bias controlled, which implied an increase in the perceived similarity of the discriminated stimuli, hurt overall performance, and elevated rated similarity. Thus, discrimination was more closely associated with 2 measures of perceived similarity than with distance and color, in support of the hypothesis.     

Resolving the latent structure of schizophrenia endophenotypes using expectation-maximization-based finite mixture modeling

Prior research has focused on the latent structure of endophenotypic markers of schizophrenia liability, or schizotypy. The work supports the existence of 2 relatively distinct latent classes and derives largely from the taxometric analysis of psychometric values. The present study used finite mixture modeling as a technique for discerning latent structure and the laboratory-measured endophenotypes of sustained attention deficits and eye-tracking dysfunction as endophenotype indexes. In a large adult community sample (N=311), finite mixture analysis of the sustained attention index d' and 2 eye-tracking indexes (gain and catch-up saccade rate) revealed evidence for 2 latent components. A putative schizotypy class accounted for 27% of the sample. A supplementary maximum covariance taxometric analysis yielded highly consistent results. Subjects in the schizotypy component displayed higher rates of schizotypal personality features and an increased rate of treated schizophrenia in their 1st-degree biological relatives compared with subjects in the other component. Implications of these results are examined in light of major theories of schizophrenia liability, and methodological advantages of finite mixture modeling for psychopathology research, with particular emphasis on genomic issues, are discussed.