Abstract EN:

The purpose of the experiments described here was to demonstrate, by means of psychochysical invbestigation, that the perception of illusory forms such as the kanizsa square is generated through low-level mechanisms. Lateral interactions between local operators which are sensitive to luminance and the sign of contrast may account for the perception of brightness differences in the stimuli. Orientation-selective operators which are insensitive to the sign of contrast may account for illusory contour genesis. The mechanisms related to the activity of both types of operators are supposed to be basically independent. However, they must cooperate at critical stages of processing to generate the integration of local inputs into global representations. A first series of experiments was run to demonstrate global effects related to the perception of local brightness differences in the kanizsa square. Data obtained in a second series of experiments by means of increment threshold procedures show that local brightness differences go a long with locally increased thresholds for the detection of a small light spot. On the other hand, illusory contour formation is reflected through abrupt local threshold decreases when the target is located on that contour.