ACQUISITION OF AN AVOIDANCE REACTION TO LIGHT IN THE PROTOZOA TETRAHYMENA

B ergström , S. R. Acquisition of an avoidance reaction to light in the Protozoa Tetrahymena. Scand. J. Psychol ., 1968, 9 , 220–224.—A culture of Tetra-hymena, dividing synchronously after exposure to an alternating heat treatment, was exposed to a series of light and electric shocks paired. Samples of this culture were drawn after 1, 6, 11, 16, 21, 26, and 31 exposures to the stimulus combination and were then placed in a partially lighted chamber. With an increasing number of stimulus presentations, the proportions of the samples found in the lighted parts decreased, while they remained roughly constant in control samples which had received either shocks or light or neither of the two stimuli.     

A PARADOX IN THE PERCEPTION OF LUMINANCE GRADIENTS. III

In the second paper of this series (Bergström, 1967) a psychophysical model of certain contrast phenomena in the perception of luminance gradients was outlined on the basis of empirical findings. From this model two predictions were derived about the appearance of a steplike luminance distribution. These predictions about relations between the brightness of different parts of the distribution have been tested by means of a ranking method and a matching technique. Both predictions were confirmed.     

Regional cortical dysfunction in schizophrenic patients studied by computerized neuropsychological methods

18 RDC-diagnosed schizophrenic patients (11 men, 7 women) were compared to 84 normal men with three computerized neuropsychological methods, assumed to reflect lateralized and frontal cortical functions: (1) Bilateral Finger Tapping and Finger Alternation, (2) Bilateral Trail Making, and (3) passively perceived Necker cube reversals. Schizophrenics differed from normals by (1) inferior Tapping/Alternation but only in the right hand, (2) inferior Trail Making, most pronounced for Form B, and (3) lower frequency of Necker cube reversals. Patients with previous neuroleptic medication and prior psychiatric hospitalizations were inferior in Trail Making and had fewer Necker cube reversals. The findings were interpreted in line with recent models of schizophrenia involving a left-hemisphere dysfunction/over-activation and a frontal dysfunction.     

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.