An analysis of the VOSP Silhouettes Test with neurological patients

The Silhouettes subtest belongs to the Visual Object and Space Perception Battery, and this study looked closely at how its individual items behave. Test protocols came from 266 German-speaking patients seen for neurological reasons, with an average age of 54.8 years. Each person in the group had some form of brain pathology.

Across that sample the average score landed at 17.0, with a standard deviation of 4.6. The subtest splits into two halves of 15 items each: one set of animals, one set of objects. Those two halves correlated at only 0.45, which is a moderate figure at best. A correlation that loose raises a fair question about whether the animals and objects really belong together on one scale.

Reliability figures came out on the weak side as well, ranging somewhere between 0.62 and 0.77. Item difficulty was another problem. The sample produced large swings in how hard individual items turned out to be, and the rules for scoring responses were not spelled out clearly enough to apply consistently.

The Silhouettes did show some agreement with other measures. Rank correlations reached 0.65 with the Hooper Visual Organization Test, 0.57 with WAIS-R Block Design, and -0.45 with the SKT neuropsychological screening battery. Even so, those connections are moderate, and they do not rescue the overall picture.

Taken together, the psychometric properties seen in this group of patients fall short of what the test would need to be dependable. The work was carried out by Thomas Merten at the Klinik für Neurologie, Klinikum im Friedrichshain, in Berlin.