Recognition processes and occurrence of the dot Poggendorff illusion.

The occurrence of the dot Poggendorff illusion was assessed in two groups of naive subjects (N = 48). One group was given information on the line Poggendorff figure while a second group was not. The line Poggendorff illusion was assessed in a third group of 24 subjects. The experiment is presented in the context of the proposal that recognition of the line Poggendorff figure in the dot-figure can be a factor determining the occurrence of the dot Poggendorff illusion.