ROD VISION AS CHROMATIC VISION

S tabell , B. Rod vision as chromatic vision. Scand. J. Psychol ., 1968, 9, 282–288.—It was found (I) that the smallest quantity of light of pre-stimula-tion which produces color upon test-stimulation, stands in unique relation to the intensity of the specific threshold, and (2) that the size of the pre-and test-stimulation fields may affect the duration of the after-image. The results are judged to indicate that pre-stimulation of cones creates the disposition for the color-related response, and that the color-related response is generated centrally to the photochemical systems of the receptors.     

COLOR THRESHOLD MEASUREMENTS IN SCOTOPIC VISION: Test-stimulation varied

S tabell , U. & S tabell , B. Color threshold measurements in scotopic vision. II. Test-stimulation varied. Scand. J. Psychol ., 1968, 9, 129–132.—The color threshold curve generally coincides with the dark adaptation curve of the rods, irrespectively of test-stimulation variation, confirming the assumption that a threshold response of rods may initiate a color-related process. Variation of color threshold intensity is thus assumed to reflect variation of rod threshold intensity.     

Mental health of outpatient pediatric patients

The purpose of this study is to estimate the percentage of mental health problems in a pediatric outpatient Norwegian clinic. We used the Strengths and Difficulties Questionnaire to screen for mental health problems. Families of children aged 4–11 took part in the study, and 380 out of 982 possible families consented to take part, and 349 families contributed with questionnaire data. The main referral reasons for the patients were asthma, eneuresis and stomach pain. Mothers reported that 17.4% of boys and 17.8% of girls displayed mental clinical problems. The prevalence of problems did not differ significantly between somatic diagnostic groups. Although the study has low participation, it underlines the necessity of screening all pediatric patients for mental health problems. Future research in pediatric clinics should include factors of psychology because pediatric problems are not caused by somatics alone.     

Anxiety and Threat Perception Abnormalities in Normal Children

The current study examined the relationship between childhood anxiety and threat perception abnormalities. Children (N = 105) were exposed to stories reflecting three types of anxiety: social anxiety, separation anxiety, and generalized anxiety. From children's reactions to the stories, a number of threat perception indices were derived. Children's level of anxiety was assessed by means of questionnaires and a structured diagnostic interview. Results indicated that high levels of anxiety, as measured by questionnaires and interview, were accompanied by a high frequency of threat perception, high ratings of threat, a high frequency of threatening interpretations, high levels of negative feelings and cognitions, and an early detection of threat. Furthermore, results seemed to suggest that threat perception abnormalities were mediated by children's general level of anxiety rather than by levels of specific anxiety symptoms.     

Information matrix estimation procedures for cognitive diagnostic models

Two new methods to estimate the asymptotic covariance matrix for marginal maximum likelihood estimation of cognitive diagnosis models (CDMs), the inverse of the observed information matrix and the sandwich-type estimator, are introduced. Unlike several previous covariance matrix estimators, the new methods take into account both the item and structural parameters. The relationships between the observed information matrix, the empirical cross-product information matrix, the sandwich-type covariance matrix and the two approaches proposed by de la Torre (2009, J. Educ. Behav. Stat., 34, 115) are discussed. Simulation results show that, for a correctly specified CDM and Q-matrix or with a slightly misspecified probability model, the observed information matrix and the sandwich-type covariance matrix exhibit good performance with respect to providing consistent standard errors of item parameter estimates. However, with substantial model misspecification only the sandwich-type covariance matrix exhibits robust performance.