Calibration of probability assessments by professional blackjack dealers, statistical experts, and lay people

The question addressed in this study is whether experts are better calibrated than lay people. We investigated how well people are calibrated when they assess the probabilities of card combinations in the game of blackjack. Three groups of subjects were used: professional dealers, statistical experts, and control subjects. The results showed that experience and statistical expertise do not make people better calibrated in this task. It is argued that the concept of calibration is not wholly appropriate to describe the obtained deviations from the normatively correct responses. This is illustrated by a discriminant analysis performed on the signed deviation scores, which resulted in an almost perfect separation of the three groups, although they were overlapping with respect to calibration.     

Development of lateral asymmetry in the perception of sequentially touched fingers

In order to investigate lateral asymmetry in tactile perception, two or four fingers of normal primary school children were touched sequentially. Stimulation was either unimanual or bimanual and either verbal or nonverbal responses were required. Right hand advantage was demonstrated subsequent to uni- and bimanual stimulation in both the verbal and nonverbal response conditions. Neither an age nor a sex effect on laterality was found. Right hand advantage was affected by direction of stimulation in the bimanual condition. Left hemispheric dominance was argued to be related to the temporal nature of the tasks.     

On various causes of improper solutions in maximum likelihood factor analysis

In the applications of maximum likelihood factor analysis the occurrence of boundary minima instead of proper minima is no exception at all. In the past the causes of such improper solutions could not be detected. This was impossible because the matrices containing the parameters of the factor analysis model were kept positive definite. By dropping these constraints, it becomes possible to distinguish between the different causes of improper solutions. In this paper some of the most important causes are discussed and illustrated by means of artificial and empirical data.The author is indebted to H. J. Prins for stimulating and encouraging discussions.     

Treatment of obsessive-compulsive patients: The contribution of self-instructional training to the effectiveness of exposure

Fifteen obsessive-compulsive patients were given treatment consisting of ten sessions of gradual exposure in vivo. For half of the patients gradual exposure in vivo was preceded by self-instructional training.Treatment resulted in significant improvement on anxiety and avoidance scales, Leyton Obsessional Inventory, Self-rating Depression Scale and on ratings for anxious mood and depression. Neither the post-test nor the follow-ups 1 month and 6 months later indicated a difference between the effects of the two conditions. Self-instructional training did not enhance the effectiveness of gradual exposure in vivo.     

TEACHING THE HANDICAPPED TO EAT IN PUBLIC PLACES: ACQUISITION,GENERALIZATION AND MAINTENANCE OF RESTAURANT SKILLS

This study examined classroom-based instruction in restauranting skills for handicapped persons. Three male students were taught each of four skill components in sequential order: locating, ordering, paying, and eating and exiting. Training was implemented in a multiple baseline design across subjects and consisted of modeling and role playing in conjunction with photo slide sequences and a simulated ordering counter. The use of a menu containing general item classes and a finger matching procedure for identifying errors in the delivery of change greatly reduced the reading and math skills necessary to enter and complete the program. Periodic probes were conducted in a McDonald's restaurant prior to, during, and up to one-year following the termination of training. In addition, two probes (overt and covert observation) were conducted in a Burger King restaurant to assess further generalization to a location different from the one depicted throughout training. Results showed that students' performance on restaurant probes improved as a result of training, generalized to novel settings, maintained over an extended period of time, and was comparable to that of a normative sample of nonretarded persons.     

Foveal diplopia thresholds and fixation disparities

Comparison of the magnitude and intrinsic spread of foveal diplopia thresholds with the accuracy of ocular alignment as determined with a subjective alignment method shows that: the accuracy of alignment in the vertical direction (within 1–2 min) is remarkably good and much better than in the horizontal direction; the largest disparities occurring due to restricted alignment accuracy are usually substantially smaller than the foveal diplopia thresholds; interindividual variability in the magnitude of foveal diplopia thresholds is not due only to interindividual variability in the alignment accuracy; and the spread of foveal diplopia thresholds exceeds the spread of ocular alignment, which implies that the noise in the foveal disparity domain is not only due to the restricted alignment accuracy but also to sensory processes. Finally, the data confirm that, unlike the case with diplopia thresholds, the spread of stereoscopic thresholds is not affected by the restricted alignment accuracy.     

The linear utility model for optimal selection

A linear utility model is introduced for optimal selection when several subpopulations of applicants are to be distinguished. Using this model, procedures are described for obtaining optimal cutting scores in subpopulations in quota-free as well as quota-restricted selection situations. The cutting scores are optimal in the sense that they maximize the overall expected utility of the selection process. The procedures are demonstrated with empirical data.     

Attitude extremity,consensus and diagnosticity

Studied the effects of attitude extremity on perceived consensus and willingness to ascribe trait terms to others with either pro or anti nuclear attitudes. Results showed that attitude extremity affected consensus estimates. Trait attributions revealed a clear effect for valence, especially for the extreme attitude groups. Subjects with extreme attitudes also ascribed more traits to both pro and anti others than subjects with relatively moderate attitudes.