Competition for feature selection: Action-related and stimulus-driven competitive biases in visual search

While constantly confronted with an enormous amount of visual information, humans are highly efficient in detecting different aspects of this information on the basis of what they want to do with the objects that they see. Specifically, at any given time, only a small portion of the information available in the visual environment can be selected for conscious processing. This selection should be based on the information required for controlling current behavior, and this process is called selective attention. The present thesis aims to reveal relations between intentional and perceptual effects on how people visually search for objects in their environment. Firstly, we investigated how intentions to grasp a visual object affects visual selection of the behaviorally more relevant visual feature (objects’ orientation in space) and the behaviorally neutral feature (objects’ color). Secondly, we cautiously controlled the perceptual similarity between objects’ colors and orientations and investigated whether they are equally relevant for visual selection. The results provide strong evidence for a biased competition between the visual features. Three studies suggest that on the basis of the perceptual information about objects’ colors and orientations, visual selection is—by default—biased towards color processing. However, two of the studies also provide support for the crucial role of action-related effect on visual selection. The results indicate that intention to make a hand movement can bias the competition between the behaviorally more relevant feature (e.g. orientation) and the perceptually more salient feature (color) in visual selection.