Final answer:
The dominant eye is the one that the brain prefers for visual input and is more accurate for tasks like aiming. It is the eye one should use for sighting a firearm.
Step-by-step explanation:
The dominant eye is the eye that provides a greater degree of input to the visual part of the brain and is more precise in tasks such as aiming, which is crucial when sighting a firearm. It is generally the eye that works faster and more accurately for sighting, regardless of being on the dominant side of the body or having better vision. To identify the dominant eye, a person can perform a simple test by creating a triangular opening between the hands at arm's length and viewing a distant object through the gap with both eyes open. By alternately closing each eye, the dominant eye will be the one that keeps the object in the same position, indicating that it should be used for aiming and sighting a firearm.