Figure-Ground Perception

Figure-Ground Perception: Relating to or denoting the perception of images by the distinction of objects from a background from which they appear to stand out

In the picture, the branches make a face but some people might not be able to notice that right away.

 

Picture from: https://www.google.com/search?q=figure-ground+perception+real+examples&source=lnms&tbm=isch&sa=X&ei=Ks17UvmOAajNsQSWzYA4&ved=0CAcQ_AUoAQ&biw=1280&bih=907#q=figure+ground+perception&tbm=isch&facrc=_&imgdii=_&imgrc=dEiQXppMchENSM%3A%3BHG6-6PKAezcqMM