Psychological studies have confirmed that the brains of infants are hardwired to recognize human faces. Just like a ducking knows how to swim by instinct, humans have an instinct to seek out human faces.
This instinct was the result of natural selection as babies must have a desire to be “cute”, and gaze into their mothers face. If babies were not cute, no doubt they would have been eaten by their parents.
Our instinct to search for faces leads to some interesting “illusions”. For example, consider this un-altered Victorian tintype photograph:
Most people see the man and woman with the face of Jesus sandwiched between them.
But that’s our instincts playing tricks.
Take a closer look at the “eye” of the Jesus face, which is in-reality the face of an infant sitting in the man’s lap!
To see the "real" image: "block out the head’s “hair” with your finger. That’s just a collection of foliage in the background. The “eye” is the face the child, shadowed by a large white bonnet. The “nose” is the sleeve of the child’s shirt. And the “mustache” is the child’s arm, bent at the elbow".
This is an excellent example of innate instinct in-action.