A person cannot taste food unless it is mixed with saliva. For example, if a strong-tasting substance like salt is placed on a dry tongue, the taste buds will not be able to taste it. As soon as a drop of saliva is added and the salt is dissolved, however, a definite taste sensation results. This is true for all foods.
Tired eyes get dry, and rubbing stimulates the lacrimal glands to produce more fluid. Tiredness also closes your eyes, so you may rub to keep them open. Finally, there’s a connection between the muscles that move your eyes around and your heart. When these muscles are stimulated, a reflex slows the heart.