The absence of depth constancy in contour stereograms.

Stereoscopic surfaces constructed from Kanizsa-type illusory contours or explicit luminance contours were tested for three-dimensional (3-D) shape constancy. The curvature of the contours and the apparent viewing distance between the surface and the observer were manipulated. Observers judged which of two surfaces appeared more curved. Experiment 1 allowed eye movements and revealed a bias in 3-D shape judgment with changes in apparent viewing distance, such that surfaces presented far from the observer appeared less curved than surfaces presented close to the observer. The lack of depth constancy was approximately the same for illusory-contour surfaces and for explicit-contour surfaces. Experiment 2 showed that depth constancy for explicit-contour surfaces improved slightly when fixation was required and eye movements were restricted. These experiments suggest that curvature in depth is misperceived, and that illusory-contour surfaces are particularly sensitive to this distortion.

Alternative representations of war zone stressors: relationships to posttraumatic stress disorder in male and female Vietnam veterans.

Four conceptualizations of war zone stressor experiences were defined: traditional combat, atrocities-abusive violence, perceived threat, and malevolent environment. Items from the National Vietnam Veterans Readjustment Study (NVVRS) were reviewed for content, and stressor indexes were created. Using retrospective self-report data from the NVVRS, intercorrelations among stressor scores and between these scores and measures of posttraumatic stress disorder (PTSD) were computed for all veterans and for men and women separately. Structural equation modeling procedures followed. Results indicated that the four stressor indexes were internally consistent, reasonably distinct from one another, and influenced PTSD differentially. Men scored significantly higher than women on all 4 indexes. Whereas the pattern of relationships among the variables was comparable across genders, there was evidence that one path coefficient in the model differed for men and women.

The civilian version of the Mississippi PTSD Scale: a psychometric evaluation.

This three-part study examined the reliability and validity of the civilian version of the Mississippi Scale for Combat-Related PTSD using data from the nonveteran participants in the National Vietnam Veterans Readjustment Study. The Civilian Mississippi Scale had a raw score distribution that was roughly symmetric, with an acceptable degree of dispersion and a reasonably high internal consistency reliability coefficient. Overall, however, measurement precision was weaker than that for the military version of the instrument, and confirmatory factor analytic findings differed from those found for the military version. Preliminary investigations of validity were in the form of correlations with indices of stressful life events, a PTSD symptom count, and measures of demoralization and active expression of hostility. The Civilian Mississippi Scale emerged from the various analyses as a PTSD measure with potential but requiring further validational study and perhaps some refinement.