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)
Size Constancy in a Photograph. Size constancy refers to the fact that our peceptions of the size of objects are relatively constant despite the fact that the size of objects on the retina vary greatly with distance. These pages show some demonstrations of the power of size constancy using a photograph I have. Take a look at the photograph to the right and see if all the people in it all look reasonably the same size. Especially compare the near and far people in the photograph.