Has it ever happened to you that you look at the clouds and see the shape of an animal or some inanimate object? Or do you look at a power outlet and give you the impression of seeing a figure resembling a face? Surely, well, this phenomenon is called pareidolia

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Pareidolia is a psychological phenomenon that makes us see a face, a silhouette, a human or animal figure anywhere: in a cloud, in the stains of a toast, in a mountain, etc.

Some people do not see those faces or silhouettes at first glance, but as soon as someone mentions what they should be seeing, then the image immediately appears in their brain, and it is almost impossible to stop seeing it.

Why do pareidolias occur?

“ As soon as the baby can see, recognize the faces, and now we know that this ability is wired in our brain."

Theorized Carl Sagan in his book, "The Demon-Haunted World", published in 1995. 

A baby with just a few minutes of life, outside his mother's womb will turn his attention to something that has the general features of a face rather than something else, explains Christopher French of the British Psychological Society. And that tendency is what helps him to recognize early the face of his mother and his closest relatives. 

Our brains today are able to recognize patterns easily, and especially patterns that serve to identify faces or silhouettes. It is impressive how in only milliseconds we can detect if a face is happy, sad or angry. For example, think about how you interpret the emoticons made with the keyboard. If the line of the mouth is straight, it is a serious face. And it is also very easy to draw an angry face, with simple stripes and dots.

This is a totally unconscious reaction. Before processing the information in detail, a certain area of the brain interprets and gives meaning to what it sees, accelerates the assessment of the situation and decision making, which was (or still is) very important for survival.

This ability, while highly specialized in the processing and recognition of human faces and emotions, also works to interpret animal behavior.

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What happens at the brain level during the pareidolias?  

Researchers have studied what happens at the brain level when we recognize a face where there is none. Apparently there is an area of the brain called the facial fusiform area, which is specialized in detecting faces, and is the area that is activated when we look at someone's face.

Another region of the brain that is activated with facial pareidolia is the prefrontal cortex. It could be said that this area is what "suggests" the facial fusiform area as interpreting the received visual signals.

There are many cases of pareidolia in our daily lives, even some have become famous. The case of "The Face of Mars" it is one of these. On July 25, 1976, the Viking spacecraft took several photos of the relief of the Martian soil in the region of Cydonia.

In one of the rock formations photographed a great similarity with a human face could be observed, especially by the effect of the shadows that were projected on them, when the rays of sun arrived with a slope of 20 degrees. Subsequently, many other photos of this formation were taken, with greater resolution and without any shadows, and in those other photos the human face is no longer so clearly seen.

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References

http://www.bbc.com/mundo/noticias/2013/05/130531_ciencia_pareidolia_caras_objetos_ig

http://www.lifeder.com/pareidolia/

http://spanish.skepdic.com/carademarte.html

(The information of these websites it is on spanish, I did the traduction for the info that I used on this post)