The Poggendorff illusion effect influenced by top-down control: evidence from an event-related brain potential study

Event-related brain potentials were used to examine the neural correlates of the visual illusion effect in the Poggendorff illusion. In this study, there were three tasks, namely, illusion task 1, illusion task 2 (similar to the classical Poggendorff figures, where the two oblique lines in which individuals were prone to judge to be collinear, were not collinear in fact), and baseline task. Scalp event-related brain potential analysis revealed that (a) both illusion task 1 and illusion task 2 elicited a more negative event-related brain potential deflection (N400-600) than did baseline task, approximately 400 ms after onset of the stimuli, and (b) high-level cognitive control system is, through enhancing the influence of the context on identifying the relationships of the two oblique lines, involved in generating the Poggendorff illusion.