Spatial distance between target and irrelevant patch modulates detection in a texture segmentation task

In three texture segmentation experiments a target patch had to be detected. We studied the impact of a task-irrelevant patch in the backward mask on detection performance, and especially the modulating effects of its spatial distance to the target. It was assumed that the signals of the two texture irregularities interact as a function of their spatial distance. Experiment 1 revealed that the task-irrelevant patch impaired target detection only when the distance was small. In Experiments 2 and 3 with systematically varying distances, detection performance increased linearly with distance until a maximum point. If the task-irrelevant patch appeared outside of a critical distance, performance did not increase further with increasing distance. Our findings are discussed in terms of the biased competition account. It is proposed that the critical distance may correspond to the average receptive field size of a cortical area that is critical for target detection.