Independent control of processing strategies for different locations in the visual field.

We investigated how the selection of information-processing strategies is organized. We contrasted three alternative ways in which strategies may be controlled: a centralized mechanism, a hemisphere-specific mechanism or a local mechanism. We built on the previous observation that the size of the noise-compatibility effect (flanker effect) is influenced by observers' expectancies for compatible or incompatible arrays. In three experiments, we varied the probabilities of compatible or incompatible noise in different locations of the visual field. We found that observers can adapt their processing strategies, as indicated by changes in the size of the noise-compatibility effect, independently in the left and right hemifields. However, processing of midline stimuli is determined by the expectancies existing in the lateral locations. These data support the notion of a hemisphere- or location-specific selection of processing strategies and suggest that the strategy selection process is not unitary.