Final answer:
Two-point discrimination is a test that measures the ability to discern two distinct points of contact; fingertips have a closer point distance due to their high density of nerve endings compared to the palm, arm, or shoulder.
Step-by-step explanation:
The subject in question deals specifically with two-point discrimination, a concept in biology that refers to the ability of the skin to discern two separate points of contact as distinct stimuli. The video referenced in the question demonstrates the use of a specialized caliper to measure the minimum distance at which two points of contact can be perceived as separate on the skin's surface. The reason the distance between the caliper points is closer on the fingertips as opposed to the palm of the hand is due to the higher density of nerve endings and sensory receptors in the fingertips, which allows for more precise tactile resolution. As for the arm or shoulder, the distance at which two points are perceived separately would be greater than on the fingertip or palm due to the lower density of nerve endings in these areas.