proportions
We had to look twice to find out what’s going on in this photo. At first glance, it looks as if the young man has an extremely large head on particularly narrow shoulders. But at second glance you can see what’s really going on here.
A young woman hugs the boy, who seems to be staring so hard at his cell phone. Wearing a black shirt, his upper body seems to disappear. The effect is enhanced by the fact that the girl wears a white top. The contrast catches the viewer’s eye and creates the illusion of a body.