Definition - What does System Unit mean? A system unit is the part of a computer that houses the primary devices that perform operations and produce results for complex calculations. It includes the motherboard, CPU, RAM and other components, as well as the case in which these devices are housed. This unit performs the majority of the functions that a computer is required to do.
size constancy - the tendency to perceive the veridical size of a familiar object despite differences in their distance (and consequent differences in the size of the pattern projected on the retina of the eye)
1 Shape Constancy: No matter the changes in an object's position or orientation, the shape of the object will be perceived as constant. 2  Brightness Constancy: Objects are perceived to have a stable amount of brightness despite changes in the amount of light that hits the object.