The within-trial time course of local and global processing in a matching task

To study the time course of the global precedence, global-to-local interference, and local-to-global interference effects in a global/local matching task, we analyzed the response time (RT) and accuracy distributions using discrete-time event history analysis and conditional accuracy analysis, respectively. In the matching task, participants saw two compound shapes on either side of a screen (e.g., a circle composed of triangles on the left and a square composed of circles on the right) and were asked to indicate whether the shapes were the same or different on a global (overall shape) or local (smaller shapes) level. A global precedence effect (faster response times in the global task) was found to occur between 300 and 800 ms after stimulus onset. Local-to-global interference was found between 400 and 700 ms. Global-to-local interference was evident by early errors when the local shapes differed, and by a decreased hazard probability of response occurrence between 400 and 800 ms. These results suggest that performance depends on the dynamic interplay between three types of shape comparisons or response tendencies: between two local shapes of the same global stimulus (triggering always the "same" response), between two global shapes ("same" or "different"), and between two local shapes on the left and right of fixation ("same" or "different").