Distinctness of perceived three-dimensional form induced by modulated illumination: Effects of certain display and modulation conditions

The present study concerns the distinctness of the 3-D shape-induced on flat displays by spacemodulated illumination (“shape from shading”). The displays that we used varied in structure, hue contrast, lightness contrast, and in the number of reflectance edges present. The modulations of the illumination were a square-wave grating, a gradual modulation (a blurred grating), and an “O’Brien modulation,” which combines an edge and a gradient. The displays were compared, using the paired comparison method, as to the distinctness of the perceived 3-D form. The results showed that the structure and chromatic color of the display were important factors facilitating the distinctness of the induced 3-D shape under all the modulation conditions. The results are discussed in relation to the “vector model” for color constancy, proposed in earlier papers.     

Personality traits in patients with narcolepsy

Narcolepsy is a lifelong disorder with the main symptoms of sleep attacks and cataplexy. In this study 49 narcoleptic patients were investigated with a battery of personality inventories, covering the following personality dimensions: anxiety-neuroticism, extraversion and socialization. The results were compared with three groups: normal subject, psychiatric inpatients with anxiety and outpatients with psychosomatic complaints. The main aim was to evaluate a clinical impression of a high degree of extraversion in narcoleptic patients, which according to Eysenck's model could be related to a disturbance in the arousal regulation. Narcoleptic patients had higher anxiety-neuroticism scores than normal individuals, particularly in terms of Somatic Anxiety. They had unexpectedly low scores in some socialization scales, and were contrary to our hypothesis slightly lower in the extraversion variables, than the comparison groups. The high scores in anxiety-neuroticism personality scales may depend on an anxiety-provoking effect of central stimulant drugs and/or a lability of the autonomic regulation associated with the disorder. Further, the strain caused by the narcoleptic symptoms may result in high scores in anxiety-neuroticism scales and low scores in socialization scales, via social-learning mechanisms. However, there may also be a coupling between the genetics of narcolepsy and biologically based personality traits.     

A PARADOX IN THE PERCEPTION OF LUMINANCE GRADIENTS. II

The first paper in this series was a study on a brightness paradox in the perception of luminance gradients in space. This study tests the hypothesis that an inducing field of higher or lower luminance having a luminance acceleration in space is a necessary condition for the paradox to appear. A magnitude estimation and a constant-sum method were used. The main result was a falsification of the hypothesis. A luminance acceleration across the inducing field was not necessary but it enhanced the paradox. The results are discussed in relation to theories on neural inhibition.     

'NEURAL UNIT' IN THE PERCEPTION OF LUMINANCE GRADIENTS

The neural unit model of neural networks proposed by von Békésy was simulated on a CDC 3600 digital computer. Certain luminance gradients in space were used as input. The output of the model was compared with the results of earlier studies on the visual appearance of these gradients. The main result was that the 'predictions' made by the model did not fit all the empirical data. Certain modifications of the model are suggested.     

Kann Es Ein Argument Für Den Skeptizismus Geben? Das Epistemische Problem Der Irrtumsmöglichkeit

Summary  Is there any argument for scepticism? The epistemic problem of the possibility of error. Arguments for scepticism rest on the assumption that knowledge claims are fallible. For this reason the concept of knowledge appears to be questionable. Since it is necessary to distinguish doubts from possible doubts, the arguments for scepticism appear to be unconvincing. If we take it into account that we know something that is immune to doubt, we should draw the conclusion that, contrary to scepticism, knowledge claims have to be compatible with being fallible. Thus any knowledge claim is capable of being doubted.