Global orientation disrupts the detection of a similar local orientation

Two experiments were carried out with organised displays in order to examine the role of similarity between global and local orientation in visual search. In both experiments, distractors were organised to form a diagonal line of plus or minus 45 degrees. In experiment 1, target displays were presented tachistoscopically. Participants searched for a target letter 'Q' among distractor letters 'O'. In experiment 2, participants performed a heterogeneity task with target line segments that could have an orientation of either plus or minus 45 degrees. The target appeared partly or completely inside a distractor circle. In both experiments, the target was more difficult to detect when the critical feature aligned with the slope of the global diagonal than when the feature did not align. Taken together, the two experiments suggested a sequential global-to-local processing in which the orientation of the global figure disrupts the detection of a similar local orientation.