Automaticity and attention: investigating automatic processing in texture segmentation with event-related brain potentials.

The present article deals with the question of automaticity and/or plasticity of processes in early vision. The detection of irregularities in an otherwise homogeneous surrounding, as studied in texture segmentation tasks, is considered an example of an automatic process in the processing of visual information. Participants in texture segmentation experiments are usually instructed to respond to the texture stimuli, i.e. attention is completely allocated towards them. Automaticity, however, would imply that processing takes also place when no attention is allocated to the texture stimuli and participants, e.g. perform another primary task. We investigated the automaticity of texture segmentation by recording Event-related potentials which allow to investigate processing also when no overt response is given. Three experiments investigated the role of attention in texture segmentation by varying task relevance of the texture stimuli. Participants had to either discriminate homogeneous or inhomogeneous textures or had to perform a different primary task of varying complexity. Two components were found to be sensitive to texture segmentation, a posterior N2 and a positivity within the P3 time interval. Both components were also observed when texture segmentation was task-irrelevant. However, while the posterior N2 was not affected by the complexity of the primary task and thus showed some degree of automaticity, the P3 was found to be dependent on the attentional resources left over by the primary task.