A global factor in the Hermann grid illusion or an artifact?

Ln the first of the present experiments, subjects were required to estimate the strength of the Hermann grid illusion in grids containing various numb ers of intersections even though those grids were not actually presented. T he positive relationship found by Wolfe (1984) for real grids was, neverthe less, replicated. It is argued that this suggests that a response bias migh t have been the source of his effect (although other possibilities are also noted). In addition, in a second experiment, subjects who were not aware o f the fact that grid size was being manipulated (i.e., between subjects) sh owed no consistent effect of that factor, thus supporting the same suggesti on.