Results Of Psychophysical Studies Research Articles

Symmetrical patterns in natural images

One of the approaches to image analysis is based on the use of visual alphabets comprising the compact patterns characteristic of the images of a particular class. Elements of these alphabets can be either obtained from a theoretical model describing the basic image structures or extracted directly from the training sets. Symmetric patterns characteristic of the images of outdoor scenes were investigated in this study. The choice of this pattern class is driven by the fact that the objects of interest usually have at least local symmetry. Furthermore, selection of only symmetric patterns allows most fragments of random textures that in most cases do not have symmetry to be dismissed. The image set used in this study comprised 829 monochromatic photographs showing natural objects and textures at different scales. Fragments with diameters of 13 pixels having 1 of 9 symmetry types were selected from this set. The obtained sets of symmetric fragments were processed using a density-based spatial clustering of applications with noise (DBSCAN) cluster analysis algorithm, which allows clusters of arbitrary shape to be analyzed. Fifteen pattern types were obtained; five of them have not previously been used as elements of visual alphabets. Most of the obtained patterns have reflection symmetry, which agrees with the results of psychophysical studies, according to which reflection symmetry is identified faster than other symmetry types. The obtained data can be used for the formation of elements of visual alphabets as well as for synthesizing the stimuli for the experiments in the field of vision physiology.

Modern interpretation of the results of psychophysical studies of the threshold of visual perception of light

This paper shows that there currently are difficulties with the traditional interpretation of psychophysical experiments for determining the energy threshold of light perception. The functioning of the retina in the threshold regime is analyzed using models that give a new interpretation of these tests and that take into account the achievements of physiological studies of threshold vision.

Influence of Task Complexity on Manual Asymmetries

The degree of manual asymmetry is generally assumed to vary with task complexity. However, task complexity as a factor in manual asymmetries has rarely been examined directly. Further, the results of psychophysical studies indicate that manual asymmetry increases with task complexity, while physiological studies consistently report a reduction of manual asymmetries in more complex tasks. The use of different tasks (rather than different complexity levels within a given task) in many psychophysical studies might result in this inconsistency. This study investigated the influence of task complexity on manual asymmetries in 70 right-handed subjects. We used three complexity levels within a finger-tapping paradigm. A strong advantage of the preferred hand was particularly pronounced in the simple finger-tapping task. When the task was more complex, the advantage of the preferred hand, and thus, the manual asymmetry significantly decreased or disappeared. These results support previous suggestions that simple motor tasks involve localised neural networks confined to one cerebral hemisphere, while complex motor tasks are controlled by more widely distributed neuronal assemblies that involve both hemispheres. However, the influence of task complexity on manual asymmetry seems not to be monotonic.