Statistical significance tests for binormal ROC curves

Statistical significance tests are derived and evaluated for measuring apparent differences between an obtained and an expected binormal ROC curve, between two independent binormal ROC curves, and among groups of independent binormal ROC curves. A binormal ROC curve is described by two parameters which represent the spread of the means and the ratio of the standard deviations of the two underlying Gaussian decision variable distributions. To test the significance of apparent differences between or among ROC curves, approximate χ² statistics for each of the three tests were constructed from maximum likelihood estimates of the two parameters defining the binormal ROC curve. The performance of each test statistic was evaluated by simulating five-category rating scale data with equal numbers of noise and signal-plus-noise trials (set at 50, 250, and 500) for each of three typical ROC curves. For the significance test involving only one ROC curve, rating scale data were generated from the chance diagonal of the ROC space also. Although test performance was found to be somewhat dependent on the number of trials and on the location of the ROC curve in the ROC space, comparisons of the obtained and expected fractions of (falsely) significant results at various α levels showed the proposed statistical significance tests to be reliable under practical experimental conditions.     

Syntactic influences on stuttering in young child stutterers

This study examined the location and rate of stuttering in the spontaneous speech of nine young stutterers (4.0–6.6 yr) in relation to certain aspects of syntax. It was designed to answer the following questions: Is there more stuttering at clause onset (boundary) than at other points in the clause? Does the type of clause influence rate of stuttering? Is there more stuttering on complex than on simple sentences? The syntactic analysis defined 10 clause types (seven pertaining to complex sentences and three pertaining to simple sentences); clause boundaries (taking into account “filler” words occuring in such positions); and hierarchical constituent structure within sentences. Stuttering was found with significantly greater frequency at clause boundaries than at internal (nonboundary) positions of clauses. This was apparent for nine of the 10 clause types, the exception being complement clauses. The word “and” at the beginning of simple and complex sentences provoked a high rate of stuttering. The hierarchical structure within the clause did not influence the location of stuttering, and sentence complexity was not a factor in the rate of stuttering.     

The relationship between arousal and positive self-presentation

Investigated the validity of the hypothesis that subjects would experience arousal if they received information suggesting that they were presenting themselves to others in a negative manner. Twenty-seven subjects were randomly assigned to a control, evaluation apprehension, or negative feedback group. Subjects' heart-rate was continuously monitored as subjects' rated a series of photographs. Subjects in the evaluation apprehension group were given a cue as to how to present themselves positively whereas subjects in the negative feedback group were told, following their response to the 15th photograph, that their responses suggested maladjustment. Heart-rate change above a baseline measure revealed that an increase in heart-rate occurred only when subjects were informed that they were transmitting negative information. Such a finding supports a positive self-presentation explanation of subject motives in the psychological experiment.     

A method for identifying eggs laid by individual birds

A method for identifying eggs laid by different subsections or individual members of groups of domestic hens is described. Fat-soluble dyes are placed in gelatin capsules and fed to selected birds. These dyes produce discrete colored bands in the yolks of eggs laid by those birds. The presence of dye in eggs can be detected through the shell, and different patterns of rings can be distinguished by boiling and sectioning eggs. Application of the method to other species and other circumstances is considered.     

Metalinguistic awareness and language development

Thirty-six 3- and 4-year-old children were given a battery of six metalinguistic tasks and two measures of language development: the Peabody Picture Vocabulary Test and a sentence comprehension test. The results clearly showed that the majority of preschoolers were able to make at least some metalinguistic judgments, and that metalinguistic performance improved with age. Furthermore, overall performance on the metalinguistic tasks was significantly correlated with each language measure when the effects of age were partialed out. In contrast, the correlation between age and metalinguistic performance was not significant once the effects of both language measures were partialed out. These data demonstrate that preschoolers' metalinguistic abilities are more extensive than has been previously acknowledged, and that they are closely tied to other aspects of language development at this time.     

Wepman test of auditory discrimination: What does it discriminate

This study investigated auditory discrimination as a function of ethnic group membership within the same socioeconomic status (SES). Subjects were 126 randomly selected six-year-old students attending schools in the lower SES community of southeast San Diego. Only students with no known speech or hearing defects and of normal intelligence were included. They were assigned to one of three categories: Black, Chicano, or Anglo.Subjects were administered four tests in a counterbalanced design: the Wepman, the Gross, and the Ott. The latter two were developed for use with Black dialect and Spanish-speaking youngsters, respectively. The ANOVA results indicated a reliable difference between the main effects of the groups (F=40.34,p<.001) and tests (F=72.82, p<.001), with a significant interaction between tests and groups (F=44.91, p<.001). Interaction effects were evaluated with the Dunn theorem. Significant differences were found among Anglo, Black, and Chicano students on the discrimination list for Spanish sounds (Ott) and a significant Anglo/Black difference on the discrimination test for Black dialect (Gross). Contrary to previous findings, there were no differences between the groups on the Wepman Test of Auditory Discrimination (WTAD). However, there are significant differences between groups on separate items of this test.     

Counseling Women in Behavioral Self-Direction

After consciousness raising, what? Women who want to alter their socialized responses may learn the necessary skills from counselors. Teaching behavioral self-management principles in the context of women's sex role enculturation is a preventive as well as corrective approach to helping women develop increased personal effectiveness. It is also an important option for those who do not need therapy or who have found other skill training insufficient.