The investigation of eidetic images poses special problems for psychology. The principal problem is how to characterize the subjective reports of eidetic imagery. These problems have led many physcologists to question the existence, in the strict sense required by science, of eidetic images. Descriptivists and strict behaviorists claim there is no way to differentiate performances consistent with so-called eidetic images from performances consistent with extraordinary descriptive memory. According to some, then, eidetic images are just memory images .
Eidetic images are distinct from after-images.
Typically, after-images are an involuntary reaction brought about as a result of overstimulation of the retina. A flash of light, intent staring at a bright color patch, and similar events overload the retinal tissues, causing them to send signals to the brain after the source of the stimulation is removed. They do not appear to be in a fixed in a physical location. An after-image will appear to move when the eyes focus on a different location. Eidetic images, on the other hand, can be triggered by what appears to be simple visual inspection of a physical object.