Note: Most of the problems that contain "noise" are particularly difficult. Here, the noise is the crosses. Once you mentally remove them, the problem becomes trivial, but the hard part is to consciously arrive at the decision to remove them. Also: look how badly some of these crosses are depicted; yet, we do not seem to have any trouble to see them as crosses, given the overall information from all 12 boxes. The context forces us to see some of these deformed figures as crosses.