8 Perceptual Organization and Visual Target Selection

Visual information processing is linked with feature selection and integration (also known as perceptual organization). The focus of the current chapter will be on the interaction of these processes in different stages of visual information processing, giving rise to various interference effects, such as crowding, Stroop and Garner interference, as well as specific interference characteristic of letters and numbers. The stagewise organization of visual perception is reviewed based on experimental studies using behavioral responses or measurements of brain signals, including event-related potentials (ERP) and the electroencephalogram (EEG). Even though perceptual organization can be fast, it interacts with early (crowding) and late (Stroop-congruence) visuospatial target selection. In letter processing, the association with phonemes makes that letters are preferably processed analytically, giving rise to negative congruence effects; for numbers we observe congruence effects in a generic magnitude space instead of the visual space. Furthermore, depending on the stimulus, perceptual organization can also be slow in the presence of distractors.