Editing Grid illusion (section)

==Differences between the scintillating and Hermann grid illusions==
The difference between the Scintillating Grid Illusion and the Hermann Grid Illusion is that the former has dots already in place at the intersections, which is not the case for the latter. Since, at first sight, the graphs appear similar, the two illusions are occasionally confused. But the scintillating illusion does not occur with an isolated intersection, as is the case for the Hermann grid; observations suggest that a minimum of {{nowrap|3 × 3}} evenly spaced intersections with superimposed discs are required to produce the effect. This requirement suggests the participation of global processes of the kind proposed for the linking and grouping of features in an image, in addition to local processes.<ref>{{cite journal |author=Alexander, D.M. |author2=Van Leeuwen, C. |year=2010 |title=Mapping of contextual modulation in the population response of primary visual cortex |doi=10.1007/s11571-009-9098-9 |pmid=19898958 |volume=4 |issue=1 |journal=Cognitive Neurodynamics |pages=1–24|pmc=2837531 }}</ref>