pictures that you have to look at cross eyed
Autostereogram There are two ways an autostereogram can be viewed: wall-eyed and cross-eyed.[a] Most autostereograms (including those in this article) are designed to be viewed in only one way, which is usually wall-eyed. Wall-eyed viewing requires that the two eyes adopt a relatively parallel angle, while cross-eyed viewing requires a relatively convergent angle. An image designed for wall-eyed viewing if viewed correctly will appear to pop out of the background, while if viewed cross-eyed it will instead appear as a cut-out behind the background and may be difficult to bring entirely into focus.[b]
Imagination A study using fMRI while subjects were asked to imagine precise visual figures, to mentally disassemble them, or mentally blend them, showed activity in the occipital, frontoparietal, posterior parietal, precuneus, and dorsolateral prefrontal regions of the subject's brains.[23]