What is perception?  The process of perception begins with an object in the real world, called the distal stimulus or distal object.   By means of light, sound or another physical process, the object stimulates the body’s sensory organs. These sensory organs transform the input energy into neural activity—a process called transduction.

The raw pattern of neural activity is called the proximal stimulus.  These neural signals are transmitted to the brain and processed. The resulting mental re-creation of the distal stimulus is the percept. Perception is sometimes described as the process of constructing mental representations of distal stimuli using the information available in proximal stimuli.

A key concept to understand is that of amodal perception.  Amodal perception  is the perception of the whole of a physical structure when only parts of it affect the sensory receptors. For example, a table will be perceived as a complete volumetric structure even if only part of it—the facing surface—projects to the retina; it is perceived as possessing internal volume and hidden rear surfaces despite the fact that only the near surfaces are exposed to view. Similarly, the world around us is perceived as a surrounding plenum, even though only part of it is in view at any time.