How you see these shapes may depend on your culture. Why your eyes perceive the world differently from everyone else.

Pedro_P

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Would you believe your eyes?
Roman Samborskyi/Shutterstock
▼ As the old saying goes, beauty is in the eye of the beholder. But while we can appreciate that others might hold different opinions of objects we see, not many people know that factors beyond our control can influence how we perceive the basic attributes of these objects. We might argue that something is beautiful or ugly, for example, but we would be surprised to learn that the same object is perceived as a sphere by one person but as a cube by another.
The process of visual perception is a best guessscenario. When we look at something, the brain uses visual cues—sensory signals that convey information—to help work out what that thing is. This means that our perception of the world is not a simple reflection of sensory information, it is an interpretationof it.
Along with color and motion, the perception of depth is very important to help us visually perceive things. Depth helps us to understand the shape of objects and their location relative to ourselves. We need to understand it to move around our environment and interact with objects. Imagine trying to pick something up if you don’t know what shape it is, or crossing the road if you can’t accurately perceive the distance of the cars.
To perceive depth, humans and animals rely on a number of brain processes and visual cues. One of these cues is shading information: we can perceive depth by simply interpreting the patterns of light and dark on the surface of objects, without needing to refer to any other information.
In order to perceive depth from shading patterns, we must either know or assume the position of the light source that illuminates the object. By default, if the light source is not apparent, we assume that the light comes from above the object.

The circle on the left is usually perceived as convex, while the circle on the right is usually perceived to be concave.
The Conversation
Look at the image to the right. The sphere on the left will most likely appear convex (protruding outwards). This is because it is lighter at the top,  (▪ ▪ ▪)

► Please, read the full article here: Source

dushazmi

Heard the concept on TED talk too, Nice but surprising facts.