V.M. Bondarko - Dr. Sc. (Biol.), Leading Research Scientist, Pavlov Institute of Physiology RAS, Saint-Petersburg, Russia. E-mail: vmbond@gmail.com M.V. Danilova - Ph.D. (Biol.)., Leading Research Scientist, Pavlov Institute of Physiology RAS, Saint-Petersburg, Russia. E-mail: mar.danilova@gmail.com S.D. Solnushkin - Leading Research Scientist, Pavlov Institute of Physiology RAS, Saint-Petersburg, Russia. E-mail: solnushkin@list.ru V.N. Chikhman - Ph.D. (Eng.), Head of Information Technology Laboratory, Pavlov Institute of Physiology RAS, Saint-Petersburg, Russia. E-mail: niv@pavlov.infran.ru

An important part of experimental scientific studies is development of methodology. Psychophysical measurements are one of the basic experimental techniques for studying mechanisms of visual perception. In the psychophysical experiment, stimuli with specific parameters are presented to observers; responses are delivered to the computer and stored in a database for further processing and analysis. We developed an experimental system for psychophysical studies of visual perception. The system includes software with a unique approach to the arrangement of separate program modules into a complex which presents stimuli, records responses, stores data and performs further analysis. The software is developed using Delphi to make the final product available for the users of Windows. Since Windows is not a real time system and at any moment the processor can be occupied by running a service program, special care should be taken to separate the experimental and service streams. This was done by synchronizing the experimental programs with distal devices (monitor frame rate, etc.). The core of experimental programs provides also an access to a database where infor-mation about observers, test objects, parameters of experimental procedures and observers` responses are recorded. During instal-lation of the programs the necessary Delphi and BDE-modules supporting database are also installed on the experimental computer. To ensure true stimuli duration for short presentation intervals (10-50 ms) to synchronize the stimuli presentation with the beginning of the monitor frame special services of the library DirectX are used instead of the component "Timer". Using the same core structure several sets of programs are developed: (i) presentation of fragmented contour images and generation of the matrices of correct responses; (ii) presentation of fragmented images under condition of forward and backward masking; (iii) programs for studying the influence of objects of various shapes on the recognition of test objects. One of the important aspects of visual perception is attention and its influence in crowding-effect phenomena. Special programs were developed to study central and peripheral crowding effects using Landolt rings as stimuli. At the stage of the image synthesis similar in shape tests and distractors were used. The tests were digital images of standard Landolt rings of the large size and threshold contrast in four orientations. The distractors were Landolt rings or similar rings without gaps. Orientation of the Landolt rings varies randomly. The distance between the test images and distractors changed from presentation to presentation. The task of the observers was to determine the orientation of the test. In one series of experiments only one distractor was presented, in other series two distractor were located symmetrically. Observer-s responses were entered into the computer by using the keyboard arrow keys to report one of the four orientations of the test Landolt ring. In the experiment, the database formed the matrices of correct and incorrect responses for various parameters of the test and distractors. It was shown that one distractor has much stronger effect on the perception of the test than the two distractors. Also, the distracting Landolt rings with gaps impaired performance at larger separations compared with the distractor in the form of a ring without a gap.

 

1. Bondarko V.M., Danilova M.V., Solnushkin S.D., CHikhman V.N. Ocenka razmera zony krauding-ehffekta pri periferijjnom predjavlenii stimulov // Fiziologija cheloveka. 2014. T. 40. № 3. S. 13-21.
2. Bondarko V.M., Danilova M.V., Solnushkin S.D., CHikhman V.N. Vlijanie dopolnitelnykh izobrazhenijj na opoznanie periferijjnogo stimula // Sensornye sistemy. 2014. T. 28. № 2. S. 3-13.
3. Bondarko V.M., Danilova M.V., Solnushkin S.D., CHikhman V.N. Issledovanie krauding-ehffekta dlja stimulov nizkogo kontrasta i bolshogo razmera v centre polja zrenija // EHksperimentalnaja psikhologija. 2015. T. 8. № 2. S. 5-20.