Q.How does perception of space take place?

We perceive space in three dimensions even though the retinal image is flat and two-dimensional, because our visual system converts this flat image into a three-dimensional experience using depth cues. …

Space refers to the visual field or surface within which objects exist, move, and can be located; the physical space in which we live has three dimensions, and our perception of it includes not just the spatial attributes of individual objects (their size, shape, direction) but also the distances between different objects.

This presents an interesting problem, because the image that is actually formed on our retina is flat -- two-dimensional, carrying only left-right and up-down information -- and yet we clearly experience the world as three-dimensional, with a genuine sense of depth and distance. This is possible because we have the ability to transform, or convert, a flat, two-dimensional retinal image into a fully three-dimensional perceptual experience. This overall process of viewing the world in three dimensions is what psychologists call distance perception, or depth perception.

Depth perception is far from being a purely academic ability -- it plays a role in countless everyday activities. When driving a vehicle, depth perception allows us to judge the distance and closing speed of an approaching car; when we see a person walking down the street and want to get their attention, our sense of how far away they are helps us judge how loudly to call out to them. …