Hidden faces is a vivid manifestation of the possibility to test and train visual memory. Visual memory is the special nature of memory, based mainly on visual impressions, capable of holding and replaying extremely vivid image of a previously observed object or phenomenon. This may, and often does also include saturated images on other channels of perception (auditory, tactile, movement, taste, smell, etc.). In some form and degree eidetism is inherent in every human being, especially in childhood or adolescence, but vivid displays of these abilities are quite rare.