Visual attention and perceptual grouping

Perceptual organization is thought to involve an analysis of bothtextural discontinuities andperceptual grouping. In earlier work, we found that textural discontinuities were detected normally even when visual attention was engaged elsewhere. Here we report how perceptual grouping is affected when visual attention is engaged by a concurrent visual task. To elicit perceptual grouping, we used the Gestalt demonstrations of grouping on the basis of proximity and of similarity. Four tasks were investigated, some requiring the observer to discriminate between horizontal and vertical grouping, and some requiring the observer to merely detect the presence or absence of grouping. Visual attention was engaged at the center of the display by a form identification task. The detection of a textural discontinuity served as a control task. Concurrent form identification conflicted with all four grouping tasks, resulting in a significant reduction of grouping performance in each case. No performance reduction was observed when either form identification or grouping discrimination was combined with the detection of a textural discontinuity. These results suggest that perceptual grouping and form identification compete for visual attention, whereas the detection of a textural discontinuity does not.     

Subjective quality of life of surgically treated glioma patients undergoing polychemotherapy

25 patients with glioma were questioned as to how they apprehended and appreciated their state of health and their psychosocial situation 1 1/2 years (s = 4 months) after the start of their postoperative polychemotherapy. In their opinion, their health was relatively good, that is, they claimed to suffer little pain, few complaints, little feeling of inadequacy, few fears for the future. They regarded the mode of treatment as being somewhat more inconvenient. Such an unexpectedly positive response, in view of the poor prospect, raises the question as to its provenance. A significant cause is seen in the organic psycho-syndrome, and its significance is made the subject of the concluding discussion, with reference to adaptation mechanisms and specifics of the illness.     

RELATIONS BETWEEN PREDICTION- AND ESTIMATION-RESPONSES IN CUE-PROBABILITY LEARNING AND TRANSFER

B auer M arianne Relations between prediction- and estimation-responses in cue-probability learning and transfer. Scand. J. Psychol ., 1972, 13 , 198–207. —Comparisons were made between prediction- and estimation-responses, preceded by training with different types of responding and when task probabilities were shifted. The main results were: ( a ) differential effects of procedure of learning and shift in task structure on predictions and estimates support the hypothesis of two different processes, ( b ) estimates as indicators of probability learning reflect traits assumed to characterize the perception process, viz. sensitivity to shifts in probabilities, and robustness against influence from procedure of learning, and ( c ) prediction-responses were affected in the direction of more extreme responses by simultaneous estimation, which result strengthens the supposition that probability estimates are insufficient as indicators of the complete perception process in a prediction task.     

Magnetoencephalography--current trends

The review deals with the method of magnet-encephalography. The physical principles and the most important technical conditions to put into practice this method are mentioned. Comparing with the electroencephalography this method shows various advantages, what leads to its intensive use for the localisation of components of evoked potentials, for the magnet-encephalographic record of the brain activity of the human fetus, and for the localisation of epileptic foci in therapy resistant epileptics.     

Perceptual scaling of synthesized musical timbres: Common dimensions,specificities, and latent subject classes

To study the perceptual structure of musical timbre and the effects of musical training, timbral dissimilarities of synthesized instrument sounds were rated by professional musicians, amateur musicians, and nonmusicians. The data were analyzed with an extended version of the multidimensional scaling algorithm CLASCAL (Winsberg & De Soete, 1993), which estimates the number of latent classes of subjects, the coordinates of each timbre on common Euclidean dimensions, a specificity value of unique attributes for each timbre, and a separate weight for each latent class on each of the common dimensions and the set of specificities. Five latent classes were found for a three-dimensional spatial model with specificities. Common dimensions were quantified psychophysically in terms of log-rise time, spectral centroid, and degree of spectral variation. The results further suggest that musical timbres possess specific attributes not accounted for by these shared perceptual dimensions. Weight patterns indicate that perceptual salience of dimensions and specificities varied across classes. A comparison of class structure with biographical factors associated with degree of musical training and activity was not clearly related to the class structure, though musicians gave more precise and coherent judgments than did nonmusicians or amateurs. The model with latent classes and specificities gave a better fit to the data and made the acoustic correlates of the common dimensions more interpretable.     

Social facilitation during the initial stage of motor learning: a re-examination of Martens' audience study

This study partially replicated Martens' (1969a) social-facilitation study of motor behavior. His very robust performance findings provided impressive confirmation for Zajonc's hypothesis, and his arousal findings have since been used as evidence for a nonlearned-drive basis for social facilitation. The present study also extended Martens' investigation by examining the separate and combined effects of an audience and videotape camera. The effects due to the presence of the audience and camera were not additive; instead, the audience detrimentally affected subjects' performance consistency and the camera resulted in more trials with errors greater than 30 msec after the performance criteria had been attained. Martens' most robust findings for constant error were not replicated, nor were some of his physiological arousal findings. His pattern of constant error results over all trials is atypical of known learning strategies that subjects use to reduce error over successive trials. Overall, audience effects accounted for only a very small portion of the variance.     

Irrelevant differences in the "same"--"different" task

This article examines the effects of irrelevant information on the multidimensional "same"--"different" task. Subjects were instructed to compare two geometric figures with respect to certain attributes but to ignore other attributes in making the "same"--"different" decision. The irrelevant attributes were chosen in such a way that they could not easily be ignored to see how the existence of irrelevant differences would affect the comparison process. As expected, the overall latencies were longer than is usually found in tasks with no irrelevant differences. However, the nature of the comparison process appeared unchanged. The usual finding of a "fast-same" phenomenon persisted even when irrelevant information was present. The similarity of the results in this task to results in the "same"--"different" task with no irrelevant features supports the idea that the same comparison mechanism is used whether or not irrelevant differences are present in the stimulus pairs. The results suggest a more general-purpose comparison mechanism than is usually included in models of this task. Two-process models of visual comparisons are thus ruled out entirely. A modified version of Krueger's noisy-operator theory does appear consistent with the results.