Vaughan of Mind Hacks discusses an unusual case human's seeing meaning - specifically, in this case, a human face - in random data. He tells it better than I do:
This is quite possibly the oddest example of an illusory face I have ever discovered.
Seeing meaningful information in meaningless data is a psychological effect known as pareidoia or apophenia and this is an example that was published in the Journal of the Royal Society of Medicine in 1996:
The case of the haunted scrotum
A 45-year-old man was referred for investigation of an undescended right testis by computed tomography (CT). An ultrasound scan showed a normal testis and epididymis on the left side. The right testis was not visualized in the scrotal sac or in the right inguinal region. On CT scanning of the abdomen and pelvis, the right testis was not identified but the left side of the scrotum seemed to be occupied by a screaming ghostlike apparition (Figure 1). By chance, the distribution of normal anatomical structures within the left side of the scrotum had combined to produce this image. What of the undescended right testis? None was found. If you were a right testis, would you want to share the scrotum with that?
J R Harding
Consultant Radiologist, Royal Gwent Hospital