The Blindspot is a gaze-contingent technique that parametrically masks central vision. Therefore the Blindspot allows us to infer how effectively extrafoveal information is used to solve the task at hand.
In the example below, a Western Caucasian observer is learning a face with a 2 degrees Blindpsot aperture:
By using the Blindspot, we have shown that the well-established eyes-mouth pattern for Westerners shifted progressively towards the typical Eastern central fixation pattern for larger Blindspots.
Miellet, S., He, L., Zhou, X., Lao, J. & Caldara, R. (2012). When East meets West: gaze-contingent Blindspots abolish cultural diversity in eye movements for faces. Journal of Eye Movement Research, 5(2):5, 1-12 [PDF]