Perception is the process of organizing and interpreting sensory information so that it becomes meaningful. It transforms the raw data of sensation into the experienced world of objects, events, and spatial layout.

Bottom-up processes begin with the sensory receptors and build toward more complex representations. Top-down processes use knowledge, expectations, and context to shape what is perceived. The two interact continuously. Illusions reveal the constructive nature of perception: the same sensory input can yield different percepts depending on organization and prior experience. Perceptual constancies allow objects to appear stable despite continually changing retinal images.

Attention selects which aspects of the sensory input receive further processing. Without perception, sensation would remain an unstructured flux. With it, the observer inhabits a world of recognizable things and predictable relationships.

Seeing, hearing, and feeling are not passive recordings. They are active constructions performed by the perceptual system.